- 08 mai 2010 15:22
#266498
Salut,
Ça faisait longtemps que je ne l’avais pas fait. C’est l’occasion ou jamais. Au programme : des Midas, de la phylogénie, l’évolution du cerveau (ou pourquoi les pétricoles pensent pas comme les sabulicoles), des tilapias qui voient violet, de la génomique (ça je suis à peu près sûr que personne demandera le papier, et d’ailleurs vous êtes combien à savoir ce qu’est la génomique ???), des femelles incubantes en hypoxie, des mâles dominants qui auraient une meilleure audition, encore de la vision (là j’y comprends pas grand-chose…), des tilapia qui ont chopé l’herpès (enfin un virus qui ressemble à ça pour être exact), comment rendre vos cichlidés plus intelligents, de la génétique de discus (non c’est pas ce que vous croyez), de la phylogénie de Tropheus (non, svp sortez pas de bazooka), de la plasticité phénotypique de la vision (ben oui maintenir les poissons dans le noir, ça leur fait de l’effet), comment rendre vos cichlidés moins agressifs en jouant avec la lumière (ca marche au moins sur vos dimerus si vous en avez), que se passe-t-il dans la tête d’un mâle en pleine ascension sociale, de la phylogénie de vers parasites (qui n’intéressera personne ici…), de la génétique de la coloration des haplos du Victoria (ou pourquoi celui là il est jaune et l’autre il est rouge), le constat que nos cichlidés tapent plus facilement sur les dominants des autres espèces que sur les dominés, des hormones de burtoni (qui n’intéresseront personne…), du stress chez des tilapia (qui n’intéressera encore une fois personne), du sexe des tilapias (non ça parle encore de génétique…), de la viabilité des hybrides et de la divergence entre espèces (ça, ça devrait en intéresser beaucoup, quoique…), de la mobilité spermatique des burtoni, des récepteurs d’oestrogènes de tilapia, de l’évolution génomique des midas (qui malheureusement intéressera pas grand monde), de la coloration des midas (oui encore eux), des préférences sexuelles chez les Nyassachromis, encore des gènes opsin, du constat que les nigro explorateurs réagissent moins vite face à un prédateur (je suis curieux de voir leur robot lol, faut que je trouve l’article !), des mangeurs d’écailles asymétriques, de l’introgression entre zebra et fuelleborni, de la biogéographie de Cichla, encore de la vision de cichlidé, de la toxicologie (suis pas fan, mais bon…), de la détermination du sexe chez les cichlidés du Malawi, des cellules intestinales de poisson, de la morphométrie de Tropheus (avec des femelles à grosse bouche), encore du stress chez les tilapia (ils ont pas de bol !), un peu de biologie cellulaire, des enzymes de tilapia, des chromosomes B au Victoria, encore du stress chez les tilapias (à croire que les mecs sont des sadiques qui adorent asphyxier leurs poissons !), et après ça, d’autres vont les intoxiquer aux métaux lourds (sadiques je vous dis !), encore des hormones de tilapia, après ça, ils leur refilent des champignons pathogènes, encore des enzymes de tilapia, de la différenciation du sexe de tilapia en boîte de pétri, des tilapias qui sentent les odeurs des poissons rouges, de la génétique des populations de Pseudocrenilabrus, des variations du niveau du lac Malawi et de l’expansion des populations de pétricoles, et c’est tout pour la période de janvier 2010 à aujourd’hui (hors descriptions scientifiques).
Si vous voulez des pdf, faites moi signe, je dois avoir accès à la plupart d’entre eux. Et préparez une bonne dose d’aspirine !
Séb
Local variation and parallel evolution: morphological and genetic diversity across a species complex of neotropical crater lake cichlid fishes.
Philos Trans R Soc Lond B Biol Sci. 2010 Jun 12;365(1547):1763-82.
Elmer KR, Kusche H, Lehtonen TK, Meyer A.
The polychromatic and trophically polymorphic Midas cichlid fish species complex (Amphilophus cf. citrinellus) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic diversification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, sampled from six crater lakes (maximally 1.2-23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic diversity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early divergence of each crater lake colonization, followed by intralacustrine diversification and speciation by ecological adaptation and sexual selection.
Multilocus phylogeny and rapid radiations in Neotropical cichlid fishes (Perciformes: Cichlidae: Cichlinae).
Mol Phylogenet Evol. 2010 Jun;55(3):1070-86. Epub 2010 Feb 21.
López-Fernández H, Winemiller KO, Honeycutt RL.
Neotropical cichlid fishes comprise approximately 60 genera and at least 600 species, but despite this diversity, their phylogeny is only partially understood, which limits taxonomic, ecological and evolutionary research. We report the largest molecular phylogeny of Neotropical cichlids produced to date, combining data from three mitochondrial and two nuclear markers for 57 named genera and 154 species from South and Central America. Neotropical cichlids (subfamily Cichlinae) were strongly monophyletic and were grouped into two main clades in which the genera Retroculus (Tribe Retroculini) and Cichla (Cichlini) were sister to a monophyletic group containing all other lineages. This group included the tribes Chaetobranchini, Astronotini, Geophagini, Cichlasomatini and Heroini. Topological comparisons with previously published hypotheses indicated that our results are congruent with recent analyses of the tribe Cichlasomatini, but significantly more likely than published hypotheses for Geophagini, Heroini and the entire Cichlinae. Improved resolution and support are attributed to increased taxon sampling and to the addition of taxa never before included in phylogenetic analyses. Geophagini included two major subclades congruent with our own previous findings but more strongly supported; we also found a new and strongly supported sister-group relationship between Guianacara and Mazarunia. Cichlasomatini relationships were similar to recently proposed topologies, but contrastingly, we found a monophyletic Cichlasoma and support for a monophyletic grouping of the Aequidens diadema and A. tetramerus groups. Three basal South American Heroini lineages were recovered: (Hypselecara+Hoplarchus), Pterophyllum, and a grouping we refer to as mesonautines. Three other South American clades, caquetaines, Australoheros and the 'Cichlasoma'festae group, were nested within Central American clades. Most Heroini diversity was divided into two relatively well-supported large groups: the Southern Central American Clade, including clades herein referred to as nandopsines, caquetaines and amphilophines, and the Northern Central American Clade, including astatheroines, tomocichlines and herichthyines. Some of these groups have been previously identified, but often with different taxonomic compositions. Further resolution of Neotropical cichlid relationships, especially within the large amphilophine clade of Heroini, will require additional phylogenetic analysis. Nevertheless, the topology from this study provides a robust phylogenetic framework for studying evolutionary diversification in Neotropical cichlids. Significantly-short branches at the base of Geophagini and Heroini are compatible with early bursts of divergence that are characteristic of adaptive radiations. This pattern suggests diversification of Neotropical cichlid genera occurred rapidly, with subsequent convergent, adaptive ecomorphological diversification among and within South and Central American clades. 2010 Elsevier Inc. All rights reserved.
Brain diversity evolves via differences in patterning.
Proc Natl Acad Sci U S A. 2010 May 3. [Epub ahead of print]
Sylvester JB, Rich CA, Loh YH, van Staaden MJ, Fraser GJ, Streelman JT.
Differences in brain region size among species are thought to arise late in development via adaptive control over neurogenesis, as cells of previously patterned compartments proliferate, die, and/or differentiate into neurons. Here we investigate comparative brain development in ecologically distinct cichlid fishes from Lake Malawi and demonstrate that brains vary among recently evolved lineages because of early patterning. Divergence among rock-dwellers and sand-dwellers in the relative size of the telencephalon versus the thalamus is correlated with gene expression variation in a regulatory circuit (composed of six3, fezf2, shh, irx1b, and wnt1) known from model organisms to specify anterior-posterior (AP) brain polarity and position the shh-positive signaling boundary zona limitans intrathalamica (ZLI) in the forebrain. To confirm that changes in this coexpression network are sufficient to produce the differences we observe, we manipulated WNT signaling in vivo by treating rock-dwelling cichlid embryos with temporally precise doses of LiCl. Chemically treated rock-dwellers develop gene expression patterns, ZLIs, and forebrains distinct from controls and untreated conspecifics, but strongly resembling those of sand-dwellers. Notably, endemic Malawi rock- and sand-dwelling lineages are alternately fixed for an SNP in irx1b, a mediator of WNT signaling required for proper thalamus and ZLI. Together, these natural experiments in neuroanatomy, development, and genomics suggest that evolutionary changes in AP patterning establish ecologically relevant differences in the elaboration of cichlid forebrain compartments. In general, variation in developmental patterning might lay the foundations on which neurogenesis erects diverse brain architectures.
Electrophysiological assessment of spectral sensitivity in adult Nile tilapia Oreochromis niloticus: evidence for violet sensitivity.
Lisney TJ, Studd E, Hawryshyn CW.
J Exp Biol. 2010 May;213(Pt 9):1453-63.
The cichlid fish radiations of the African Great Lakes are an important model for evolutionary biology. Cichlids have diverse colour vision systems and predominately express three cone visual pigments. However, rare populations of spectrally distinct cones have been found in a number of species, but it is not known whether they contribute to spectral sensitivity. Adult Nile tilapia, Oreochromis niloticus, an ancestral outgroup to the cichlid radiations in the Great Lakes, have three cone types: short-wavelength sensitive (SWS), medium-wavelength sensitive (MWS) and long-wavelength sensitive (LWS) cones, but evidence from microspectrophotometry and cone opsin gene expression suggests they may also have violet-sensitive (VS) cones. We used electrophysiology to assess spectral sensitivity in this species and found evidence of four sensitivity peaks in the ranges 380-420, 440-480, 500-600 and 600-680 nm, with maximal sensitivity at longer wavelengths. The continued presence of a 380-420 nm peak under long-wavelength chromatic adapting backgrounds indicates that this is due to a VS cone mechanism not the beta-band of the LWS cone mechanism. Differences in spectral sensitivity curves recorded at different times of year revealed evidence of A1/A2 shifts. The presence of notches in the sensitivity curves and a multiple-mechanisms model used to assess cone contributions indicated that the curves are the result of four cone mechanisms (VS, SWS, MWS and LWS cones) and that chromatically opponent processes occur between mechanisms. The spectral transmittance of the lens steeply declines between 410-380 nm, limiting the short-wavelength limb of the VS cone. As adults, Nile tilapia appear to possess the necessary retinal mechanisms for colour vision. While maximal sensitivity to longer wavelengths is an adaptation to the wavelengths of light predominantly available in their natural habitats, their broad sensitivity range suggests that Nile tilapia possess a flexible, generalised visual system able to adapt to changes in visual environment in their highly variable natural habitat.
Energetics of hypoxia in a mouth-brooding cichlid: evidence for interdemic and developmental effects.
Reardon EE, Chapman LJ.
Physiol Biochem Zool. 2010 May-Jun;83(3):414-23.
We used a common-garden rearing experiment to explore environmentally induced tolerance to hypoxia in the African mouth-brooding cichlid Pseudocrenilabrus multicolor. F(1) fish originating from three field populations were grown under low or high dissolved oxygen (DO), and their resting routine metabolic rate (RMR), critical oxygen tension (P(crit)), and marginal metabolic scope (MMS) were quantified. In a second rearing experiment, we compared the RMR of brooding and nonbrooding females of low-DO origin grown under low and high DO. Fish reared under low DO had a lower P(crit) than fish reared under high DO. There was also an interaction between treatment and gender; females had a higher P(crit) than males when reared under normoxia. Variation in RMR was driven primarily by population effects, and there was an interaction between treatment and population. Regardless of population or treatment, males had a higher MMS than females. Fish reared under low DO had a higher MMS than fish reared under high DO, except for the high-DO population in which there was no treatment effect. Brooding females had a higher RMR than postbrooding females regardless of the growth treatment, indicating an energetic cost to brooding. The results suggest a strong element of developmental plasticity in P(crit) across populations and both plastic and genetic components of variation in the RMR and MMS. This study also highlights the cost of parental care in mouth-brooding fishes, which may increase the fitness of the offspring at the energetic expense of the parent, a cost that may be elevated under hypoxia.
An EST resource for tilapia based on 17 normalized libraries and assembly of 116,899 sequence tags.
Lee BY, Howe AE, Conte MA, D'Cotta H, Pepey E, Baroiller JF, di Palma F, Carleton, KL, Kocher TD.
BMC Genomics. 2010 Apr 30;11(1):278. [Epub ahead of print]
ABSTRACT: BACKGROUND: Large collections of expressed sequence tags (ESTs) are a fundamental resource for analysis of gene expression and annotation of genome sequences. We generated 116,899 ESTs from 17 normalized and two non-normalized cDNA libraries representing 16 tissues from tilapia, a cichlid fish widely used in aquaculture and biological research. RESULTS: The ESTs were assembled into 20,190 contigs and 36,028 singletons for a total of 56,218 unique sequences and a total assembled length of 35,168,415bp. Over the whole project, a unique sequence was discovered for every 2.079 sequence reads. 17,722 (31.5%) of these unique sequences had significant BLAST hits (e-value <10> 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.
Testing the carotenoid trade-off hypothesis in the polychromatic Midas cichlid, Amphilophus citrinellus.
Lin SM, Nieves-Puigdoller K, Brown AC, McGraw KJ, Clotfelter ED.
Physiol Biochem Zool. 2010 Mar-Apr;83(2):333-42.
Many animals use carotenoid pigments derived from their diet for coloration and immunity. The carotenoid trade-off hypothesis predicts that, under conditions of carotenoid scarcity, individuals may be forced to allocate limited carotenoids to either coloration or immunity. In polychromatic species, the pattern of allocation may differ among individuals. We tested the carotenoid trade-off hypothesis in the Midas cichlid, Amphilophus citrinellus, a species with two ontogenetic color morphs, barred and gold, the latter of which is the result of carotenoid expression. We performed a diet-supplementation experiment in which cichlids of both color morphs were assigned to one of two diet treatments that differed only in carotenoid content (beta-carotene, lutein, and zeaxanthin). We measured integument color using spectrometry, quantified carotenoid concentrations in tissue and plasma, and assessed innate immunity using lysozyme activity and alternative complement pathway assays. In both color morphs, dietary carotenoid supplementation elevated plasma carotenoid circulation but failed to affect skin coloration. Consistent with observable differences in integument coloration, we found that gold fish sequestered more carotenoids in skin tissue than barred fish, but barred fish had higher concentrations of carotenoids in plasma than gold fish. Neither measure of innate immunity differed between gold and barred fish, or as a function of dietary carotenoid supplementation. Lysozyme activity, but not complement activity, was strongly affected by body condition. Our data show that a diet low in carotenoids is sufficient to maintain both coloration and innate immunity in Midas cichlids. Our data also suggest that the developmental transition from the barred to gold morph is not accompanied by a decrease in innate immunity in this species.
SEQUENTIAL FEMALE ASSESSMENT DRIVES COMPLEX SEXUAL SELECTION ON BOWER SHAPE IN A CICHLID FISH.
Young KA, Genner MJ, Haesler MP, Joyce DA.
Evolution. 2010 Feb 26. [Epub ahead of print]
In many animals, sexual selection on male traits results from female mate choice decisions made during a sequence of courtship behaviors. We use a bower-building cichlid fish, Nyassachromis cf. microcephalus, to show how applying standard selection analysis to data on sequential female assessment provides new insights into sexual selection by mate choice. We first show that the cumulative selection differentials confirm previous results suggesting female choice favors males holding large volcano-shaped sand bowers. The sequential assessment analysis reveals these cumulative differentials are the result of selection acting on different bower dimensions during the courtship sequence; females choose to follow males courting from tall bowers, but choose to engage in premating circling with males holding bowers with large diameter platforms. The approach we present extends standard selection analysis by partitioning the variances of increasingly accurate estimates of male reproductive fitness and is applicable to systems in which sequential female assessment drives sexual selection on male traits.
Scale-eating cichlids: from hand(ed) to mouth.
Palmer AR.
J Biol. 2010 Feb 24;9(2):11. [Epub ahead of print]
ABSTRACT: Two recent studies in BMC Biology and Evolution raise important questions about a textbook case of frequency-dependent selection in scale-eating cichlid fishes. They also suggest a fascinating new line of research testing the effects of handed behavior on morphological asymmetry.
Genetic basis of differential opsin gene expression in cichlid fishes.
Carleton KL, Hofmann CM, Klisz C, Patel Z, Chircus LM, Simenauer LH, Soodoo N,Albertson RC, Ser JR.
J Evol Biol. 2010 Feb 23. [Epub ahead of print]
Abstract Visual sensitivity can be tuned by differential expression of opsin genes. Among African cichlid fishes, seven cone opsin genes are expressed in different combinations to produce diverse visual sensitivities. To determine the genetic architecture controlling these adaptive differences, we analysed genetic crosses between species expressing different complements of opsin genes. Quantitative genetic analyses suggest that expression is controlled by only a few loci with correlations among some genes. Genetic mapping identifies clear evidence of trans-acting factors in two chromosomal regions that contribute to differences in opsin expression as well as one cis-regulatory region. Therefore, both cis and trans regulation are important. The simple genetic architecture suggested by these results may explain why opsin gene expression is evolutionarily labile, and why similar patterns of expression have evolved repeatedly in different lineages.
Are fast explorers slow reactors? Linking personality type and anti-predator behaviour.
Jones KA, Godin JG.
Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S
Response delays to predator attack may be adaptive, suggesting that latency to respond does not always reflect predator detection time, but can be a decision based on starvation-predation risk trade-offs. In birds, some anti-predator behaviours have been shown to be correlated with personality traits such as activity level and exploration. Here, we tested for a correlation between exploration behaviour and response latency time to a simulated fish predator attack in a fish species, juvenile convict cichlids (Amatitlania nigrofasciata). Individual focal fish were subjected to a standardized attack by a robotic fish predator while foraging, and separately given two repeated trials of exploration of a novel environment. We found a strong positive correlation between exploration and time taken to respond to the predator model. Fish that were fast to explore the novel environment were slower to respond to the predator. Our study therefore provides some of the first experimental evidence for a link between exploration behaviour and predator-escape behaviour. We suggest that different behavioural types may differ in how they partition their attention between foraging and anti-predator vigilance.
HANDEDNESS AND ASYMMETRY IN SCALE-EATING CICHLIDS: ANTISYMMETRIES OF DIFFERENT STRENGTH.
Van Dooren TJ, van Goor HA, van Putten M.
Evolution. 2010 Feb 19. [Epub ahead of print]
Individual symmetry is believed to be advantageous and reflecting developmental stability, but frequency-dependent selection can also maintain polymorphisms of asymmetric phenotypes. There are many examples of so-called antisymmetry, where mirror image morphs occur at equal frequencies. With very few exceptions, these are caused by nongenetic variation. One notable exception is handedness and mouth bending variation in the scale-eating cichlid Perissodus microlepis, which has been suggested to be an example of antisymmetry determined by a single genetic locus of large effect. Here, we report that this handedness and mouth bending asymmetry are not jointly and exclusively determined by a single major locus. We found no evidence of a major locus for asymmetry and some support for a major handedness locus. Also, asymmetry is plastic in this species: it can change in adults. We suggest that behavioral handedness in this system precedes and guides morphological asymmetry.
Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids.
Mims MC, Darrin Hulsey C, Fitzpatrick BM, Todd Streelman J.
Mol Ecol. 2010 Feb 8. [Epub ahead of print]
Abstract Phenotypically diverse Lake Malawi cichlids exhibit similar genomes. The extensive sharing of genetic polymorphism among forms has both intrigued and frustrated biologists trying to understand the nature of diversity in this and other rapidly evolving systems. Shared polymorphism might result from hybridization and/or the retention of ancestrally polymorphic alleles. To examine these alternatives, we used new genomic tools to characterize genetic differentiation in widespread, geographically structured populations of Labeotropheus fuelleborni and Metriaclima zebra. These phenotypically distinct species share mitochondrial DNA (mtDNA) haplotypes and show greater mtDNA differentiation among localities than between species. However, Bayesian analysis of nuclear single nucleotide polymorphism (SNP) data revealed two distinct genetic clusters corresponding perfectly to morphologically diagnosed L. fuelleborni and M. zebra. This result is a function of the resolving power of the multi-locus dataset, not a conflict between nuclear and mitochondrial partitions. Locus-by-locus analysis showed that mtDNA differentiation between species (F(CT)) was nearly identical to the median single-locus SNP F(CT). Finally, we asked whether there is evidence for gene flow at sites of co-occurrence. We used simulations to generate a null distribution for the level of differentiation between co-occurring populations of L. fuelleborni and M. zebra expected if there was no hybridization. The null hypothesis was rejected for the SNP data; populations that co-occur at rock reef sites were slightly more similar than expected by chance, suggesting recent gene flow. The coupling of numerous independent markers with extensive geographic sampling and simulations utilized here provides a framework for assessing the prevalence of gene flow in recently diverged species.
The Casiquiare river acts as a corridor between the Amazonas and Orinoco river basins: biogeographic analysis of the genus Cichla.
Willis SC, Nunes M, Montaña CG, Farias IP, Ortí G, Lovejoy NR.
Mol Ecol. 2010 Feb 8. [Epub ahead of print]
Abstract The Casiquiare River is a unique biogeographic corridor between the Orinoco and Amazonas basins. We investigated the importance of this connection for Neotropical fishes using peacock cichlids (Cichla spp.) as a model system. We tested whether the Casiquiare provides a conduit for gene flow between contemporary populations, and investigated the origin of biogeographic distributions that span the Casiquiare. Using sequences from the mitochondrial control region of three focal species (C. temensis, C. monoculus, and C. orinocensis) whose distributions include the Amazonas, Orinoco, and Casiquiare, we constructed maximum likelihood phylograms of haplotypes and analyzed the populations under an isolation-with-migration coalescent model. Our analyses suggest that populations of all three species have experienced some degree of gene flow via the Casiquiare. We also generated a mitochondrial genealogy of all Cichla species using >2000 bp and performed a dispersal-vicariance analysis (DIVA) to reconstruct the historical biogeography of the genus. This analysis, when combined with the intraspecific results, supports two instances of dispersal from the Amazonas to the Orinoco. Thus, our results support the idea that the Casiquiare connection is important across temporal scales, facilitating both gene flow and the dispersal and range expansion of species.
The relationship between lens transmission and opsin gene expression in cichlids from Lake Malawi.
Hofmann CM, O'Quin KE, Justin Marshall N, Carleton KL.
Vision Res. 2010 Feb 8;50(3):357-63. Epub 2009 Dec 11.
The lens plays an important role in regulating the wavelengths of light that reach the retina. However, the evolutionary relationship between lens transmission and retinal sensitivity remains cloudy at best. We examined the relationship between lens transmission and opsin gene expression in a group of rapidly radiating cichlids from East Africa. Lens transmission was bimodal, either cutting off around 360 or 400 nm, and appeared to be quite labile evolutionarily. We found a strong correlation between lens transmission and SWS1 (UV) opsin gene expression, suggesting that UV transmitting lenses are adaptive in cichlids. Species which expressed high levels of SWS2B (violet) opsin varied in their lens transmission while most species that expressed high levels of SWS2A (blue) opsin had UV blocking lenses. In no instance did lens transmission appear to limit retinal sensitivity. Finally, the strong correlation that we observe between SWS1 expression and lens transmission suggests that these two traits might be coupled genetically. Copyright (c) 2009 Elsevier Ltd. All rights reserved.
Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS.
Wahidulla S, Rajamanickam YR.
Environ Sci Pollut Res Int. 2010 Feb;17(2):441-52. Epub 2009 Oct 2.
BACKGROUND, AIM, AND SCOPE: Mutagenic nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been known to arise in the environment through direct emissions from combustion sources and nitration of PAHs, primarily in the atmosphere. In the marine environment, PAHs are one of the classic anthropogenic organic pollutants, while nitrite (NO(2)(-)) is produced naturally via various biological processes like imbalance in nitrification/denitrification or eutrophication and subsequent oxygen depletion from an oversupply of nutrients. In this paper, we report the formation of PAH-DNA adducts in fish contaminated with PAHs and exposed to NO(2)(-) in the ambient water. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of the bile of the euryhaline fish Oreochromis mossambicus exposed simultaneously to field relevant sublethal concentrations of phenanthrene and NO(2)(-) and collision-induced dissociation of selected ions revealed the presence of DNA-PAH adducts. The present study indicates that, although several high sensitivity techniques have been developed for the analysis of PAH derived DNA adducts, MS/MS has emerged as a powerful tool in the detection and structure elucidation of DNA adducts. MATERIALS AND METHODS: Juvenile O. mossambicus from a local estuarine fish farm were used with increasing frequency for carcinogenicity testing and comparative cancer research. The fish were exposed to the alkylating agent phenanthrene in the presence of NO(2)(-). Composite untreated bile samples after dilution with methanol: water (1:1; v/v) were analyzed by ESI-MS. RESULTS: Several adducts could be evidenced in the bile by MS/MS. Deoxyadenosine/deoxyguanosine having a mass in the range of 450-650 amu is detected. In addition, a segment of modified dinucleotide with a mass that corresponds to a dimer consisting of a modified guanosine and a normal guanosine has also been identified in the bile. DISCUSSION: The formation of certain types of DNA adducts is a crucial step in the induction of cancer and a primary stage in mutagenesis. Phenanthrene injected by i.p. route led to the transformation of phenanthrene to N-formyl amino phenanthrene-N(6)-deoxyadenosine adduct, whereas the fish co-exposed to phenanthrene and ambient nitrite metabolizes PAH to mono-, di- as well as trinitro derivatives, which then react with DNA leading to the formation of mainly modified guanosine and adenosine adducts. In the present investigation, dinitrophenanthrene diol epoxide (DNPDE) adduct with guanosine (m/z 587) seems to be the dominant adduct in the mixture, and its presence is shown first as a comparatively less stable adduct, which decomposes to give a more stable N(2) adduct (m/z 567). CONCLUSIONS: MS/MS has proved to be useful in the rapid determination and discrimination of structurally different phenanthrene/derivatives DNA adducts in a complex mixture of fish bile co-exposed to phenanthrene and nitrite. However, the nature of metabolites formed is likely determined by the route of PAH administration, and there is a need to further define the early biochemical events of carcinogenesis in these species. RECOMMENDATIONS AND PERSPECTIVES: DNA adduct analysis in fish bile offers a promising approach to study the risk of potentiation of anthropogenic chemicals into genotoxic compounds in the presence of nitrite in the marine environment. We believe this is the first report on the formation of DNA-phenanthrene adducts on co-exposure of the fish to PAH and nitrite.
Multiple interacting Loci control sex determination in lake Malawi cichlid fish.
Ser JR, Roberts RB, Kocher TD.
Evolution. 2010 Feb 1;64(2):486-501. Epub 2009 Oct 23.
Several models have been proposed to suggest how the evolution of sex-determining mechanisms might contribute to speciation. Here, we describe the inheritance of sex in 19 fish species from the rapidly evolving flock of cichlids in Lake Malawi, Africa. We found that many of these species have a male heterogametic (XY) system on linkage group 7. Some species also segregate for a female heterogametic (ZW) system on linkage group 5 that is coincident with a dominant orange-blotch (OB) color pattern in females. The ZW system is epistatically dominant to the XY system when both are segregating within a family. Several lines of evidence suggest that additional sex-determining loci are segregating in some species. These results are consistent with the idea that genetic conflicts play an important role in the evolution of these species flocks and suggest that evolution of sex-determining mechanisms has contributed to the radiation of cichlid fish in East Africa.
Endosulfan increases seric interleukin-2 like (IL-2L) factor and immunoglobulin M (IgM) of Nile tilapia (Oreochromis niloticus) challenged with Aeromona hydrophila.
Tellez-Bañuelos MC, Santerre A, Casas-Solis J, Zaitseva G.
Fish Shellfish Immunol. 2010 Feb;28(2):401-5. Epub 2009 Nov 24.
Endosulfan is a persistent organochlorine insecticide which is extremely toxic to fish. It is known to induce immunological alterations in juvenile Nile tilapia (Oreochromis niloticus) such as increases in phagocytic activity and reactive oxygen species production of spleen macrophages. The purpose of the present study was to demonstrate the effects of acute exposure to a sublethal concentration of endosulfan (7 ppb, 96 h) on parameters of the adaptive humoral immune response of the aforementioned aquatic organism. The effect of endosulfan on the capacity of immune cells to produce interleukin-2 like (IL-2L) factor and immunoglobulin M (IgM) in response to a challenge with (1/2) LD50 of the infectious bacteria Aeromonas hydrophila was evaluated. Experimental results indicate that short, sublethal, endosulfan exposure triggers a succession of events beginning with non-specific activation of macrophages followed by an exacerbated synthesis of the IL-2L factor by activated B cells. This leads to significantly increased secretion of IgM and could in turn facilitate autoantibody production and the development of autoimmune pathologies. Copyright 2009 Elsevier Ltd. All rights reserved.
Effect of ferrous sulphate on aspartate and alanine aminotransferases of brain of Tilapia mossambica.
Nunes ES, Desai SN, Desai PV.
Food Chem Toxicol. 2010 Feb;48(2):490-4. Epub 2009 Nov 1.
Iron in the form of ferrous sulphate coming from sources such as mines, writing inks, blue pigments, dyeing industries, photography, medicine, deodorizers, disinfectants, fungicides and molluscides, etc. contributes in elevating ferrous sulphate of water bodies. The present study investigated the action of ferrous sulphate on the local fish Tilapia mossambica. Tilapia exposed to 0.001 g/L ferrous sulphate for 30 days showed reduction of cytosolic AST and ALT activities of cerebral cortex by 35.4% and 29.1%, respectively, while exposure to 0.01% ferrous sulphate promoted 49.2% and 38.4% reduction of AST and ALT activities. Similarly mitochondrial AST and ALT activities reduced by 50% and 34.8%, respectively, on exposure to 0.001 g/L ferrous sulphate while 0.01 g/L ferrous sulphate promoted 51% and 47.8% reductions of AST and ALT activities at the end of 30 days, suggesting interference in the glutamate and protein metabolism of Tilapia brain. Copyright 2009 Elsevier Ltd. All rights reserved.
Histochemical study on the intestine goblet cells in cichlid and poecilid species (Teleostei).
Leknes IL.
Tissue Cell. 2010 Feb;42(1):61-4. Epub 2009 Oct 14.
Histochemical properties of intestine goblet cells in firemouth cichlid, zebra mbuna, freshwater angelfish and platyfish are described. Goblet cells occurred regularly in the epithelial cell layer throughout the entire intestine, they were strongly coloured by alcian blue at pH 2.5. This colour got gradually weaker when the pH was reduced, but still after alcian blue at pH 0.2 these cells displayed a distinct blue colour. When the goblet cells were treated with periodic acid-Schiff (PAS), they displayed a strong purple-magenta colour. The findings that a number of goblet cells displayed various colours between blue and purple-magenta when acidic alcian blue was followed by PAS, and between blue and red-brown when acidic alcian blue was followed by neutral red, may reflect different ages or stages of development and differentiation for these cells. However, such results may also suggest a true cellular heterogeneity in the present population of goblet cells, reflecting that the intestine mucus layer has a number of roles in teleosts like lubrication, protection, immunological defence, digestion and absorption. In the ferritin injected specimens of firemouth cichlid and platyfish, a number of macrophage-like cells in intestine wall displayed Prussian blue precipitations in tissue treated with acid ferrocyanide, suggesting that these cells play a cleansing role in the intestinal wall. No ferritin uptake was seen in the intestine goblet cells and eosinophilic granule cells. Copyright 2009 Elsevier Ltd. All rights reserved.
Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids.
Stewart TA, Albertson RC.
BMC Biol. 2010 Jan 26;8:8.
BACKGROUND: While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids. RESULTS: Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids. CONCLUSIONS: We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will facilitate a better understanding of the evolution of this unique group of fishes, as well as of left-right axis determination among vertebrates in general.
Sexual dimorphism and population divergence in the Lake Tanganyika cichlid fish genus Tropheus.
Herler J, Kerschbaumer M, Mitteroecker P, Postl L, Sturmbauer C.
Front Zool. 2010 Jan 22;7:4.
ABSTRACT: BACKGROUND: With about 120 colour morphs currently assigned to six nominal species, the genus Tropheus is an ideal model to study evolutionary divergence of populations in allopatry. The morphology of Tropheus has been described as relatively static, but reproductive constraints are sexually dimorphic due to mouthbrooding in females. We analysed phenotypic variation in six populations of T. moorii and one population of T. polli using geometric morphometrics to assess morphological differences among sexes in relation to the differentiation of populations and species. RESULTS: The mean shapes differed significantly between sexes, populations, and species even though within-sex variation exceeded the divergence among populations. The first principal component of Procrustes shape coordinates revealed differences between populations and species in mouth position and ventral head shape. The second principal component reflected sex-specific shape differences, mainly comprising a relatively larger female viscerocranium and, in particular, a larger buccal area. While shape variation between populations and between sexes was primarily located in the cranial region, within-sex variation was relatively uniform across all landmarks. CONCLUSIONS: Deviations of the between-population and between-sex pattern of shape variation from that within sex indicate that the differences in head shape likely result from both adaptations to female mouthbrooding and population-specific foraging strategies.
Hyperosmotic shock adaptation by cortisol involves upregulation of branchial osmotic stress transcription factor 1 gene expression in Mozambique Tilapia.
McGuire A, Aluru N, Takemura A, Weil R, Wilson JM, Vijayan MM.
Gen Comp Endocrinol. 2010 Jan 15;165(2):321-9. Epub 2009 Aug 3.
The Mozambique tilapia (Oreochromis mossambicus) is a euryhaline species that does not survive direct seawater exposure. Cortisol is involved in re-establishing electrolyte homeostasis in seawater and is thought to play a role in allowing tilapia to cope with abrupt seawater exposure, but the mechanism(s) are far from clear. Recently, osmotic stress transcription factor 1 (OSTF1) was identified as a key signaling molecule involved in hyperosmotic stress adaptation in tilapia. Consequently, we tested the hypothesis that upregulation of OSTF1 expression by cortisol is a key response for hyperosmotic stress adaptation in tilapia. Fish were exposed to different salinities over a 24h period, while a major electrolyte disturbance and mortality was observed only with full-strength seawater exposure. Therefore, we administered cocoa butter implants of cortisol (50mg/kg) intraperitoneally to tilapia maintained in fresh water and after three days exposed these fish to full-strength seawater. There was 50% mortality in the control fish upon seawater exposure, but this was abolished by cortisol treatment. Abrupt seawater exposure did not affect plasma cortisol levels, while, as expected, exogenous administration of this steroid elevated plasma cortisol levels both in fresh water and seawater. Cortisol treatment significantly induced OSTF1 gene expression in fresh water tilapia, and also enhanced further the seawater-induced OSTF1 mRNA abundance. Plasma osmolality decreased, while gill Na(+)/K(+)-ATPase activity was suppressed in the cortisol group in seawater compared to the sham group. This corresponded with a significant reduction in gill ionocyte size and Na(+)/K(+)-ATPase activity and protein expression after seawater exposure. Cortisol did not modify liver metabolism, but significantly suppressed gill metabolic capacity in seawater. Overall, cortisol adapts tilapia to a hyperosmotic shock associated with abrupt seawater exposure. This involves upregulation of OSTF1 gene expression and a concomitant suppression of branchial metabolism in tilapia.
Cloning and molecular characterization of the glucose transporter 1 in tilapia (Oreochromis niloticus).
Hrytsenko O, Pohajdak B, Xu BY, Morrison C, van Tol B, Wright JR Jr.
Gen Comp Endocrinol. 2010 Jan 15;165(2):293-303. Epub 2009 Aug 3.
Facilitative glucose transporters (GLUTs) are responsible for passively transporting monosaccharides across the plasma membrane. We sequenced and characterized the Nile tilapia (Oreochromis niloticus) GLUT-1 (tGLUT-1) cDNA and genomic DNA. Using rapid amplification of the cDNA ends (RACE), two tGLUT-1 transcripts were detected differing in the length of the 3' untranslated region, 2851 and 4577 bp. Translated tGLUT-1 is a 490 amino acid product, which shares 74% homology with that of humans. Computer analysis of the amino acid sequence predicted 12 transmembrane domains, which are conserved in the GLUT-1 of various species. The tGLUT-1 gene spans more than 11 kb, and similar to the mammalian GLUT-1 genes has a 10 exon, 9 intron organization. Potential promoter regulatory elements have some similarity to those recorded for human, mouse, and rat GLUT-1 genes. Tissue expression studies revealed both GLUT-1 transcripts in liver, Brockmann bodies (BB), heart, small intestine, adipose tissue, white and red muscle, gill, spleen, pituitary gland, and brain. The highest level of expression was detected in tilapia heart, followed by BB, brain, and muscle. Protein based food and glucose had minor or no effects on the level of tGLUT-1 expression in most tissues. The tGLUT-1 mRNA level was significantly induced by glucose and food only in white muscle. Current results suggest that tGLUT-1 is similar to the GLUT-1 of other teleost species and mammals at the genomic, mRNA, and amino acid levels, supporting the concept that tGLUT-1 functions as a ubiquitous basal level glucose transporter.
Genetic variation and demographic history of the Haplochromis laparogramma group of Lake Victoria-An analysis based on SINEs and mitochondrial DNA.
Mzighani SI, Nikaido M, Takeda M, Seehausen O, Budeba YL, Ngatunga BP, Katunzi, EF, Aibara M, Mizoiri S, Sato T, Tachida H, Okada N.
Gene. 2010 Jan 15;450(1-2):39-47.
More than 500 endemic haplochromine cichlid species inhabit Lake Victoria. This striking species diversity is a classical example of recent explosive adaptive radiation thought to have happened within the last approximately 15,000 years. In this study, we examined the population structure and historical demography of 3 pelagic haplochromine cichlid species that resemble in morphology and have similar niche, Haplochromis (Yssichromis) laparogramma, Haplochromis (Y.) pyrrhocephalus, and Haplochromis (Y.) sp. "glaucocephalus". We investigated the sequences of the mitochondrial DNA control region and the insertion patterns of short interspersed elements (SINEs) of 759 individuals. We show that sympatric forms are genetically differentiated in 4 of 6 cases, but we also found apparent weakening of the genetic differentiation in areas with turbid water. We estimated the timings of population expansion and species divergence to coincide with the refilling of the lake at the Pleistocene/Holocene boundary. We also found that estimates can be altered significantly by the choice of the shape of the molecular clock. If we employ the nonlinear clock model of evolutionary rates in which the rates are higher towards the recent, the population expansion was dated at around the event of desiccation of the lake ca. 17,000 YBP. Thus, we succeeded in clarifying the species and population structure of closely related Lake Victoria cichlids and in showing the importance of applying appropriate clock calibrations in elucidating recent evolutionary events.
Purification and characterization of trypsin from the intestine of hybrid tilapia (Oreochromis niloticusxO.aureus).
Wang Q, Gao ZX, Zhang N, Shi Y, Xie XL, Chen QX.
J Agric Food Chem. 2010 Jan 13;58(1):655-9.
Trypsin from the intestine of hybrid tilapia (Oreochromis niloticus x O.aureus) was purified by the following techniques: acetone precipitation, ammonium sulfate fractionation, Sephacryl S-200 gel filtration, and DEAE-sephacel ion exchange chromatography. The purified enzyme was determined to be homogeneous by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecular weight was estimated as 22,000 Da. The optimum pH and temperature of the enzyme for the hydrolysis of casein were determined to be 9.0 and 60 degrees C, respectively. The enzyme was stable over a broad pH range from 7.0 to 12.0 at 30 degrees C, and the enzyme was inactive at temperatures above 50 degrees C. The behavior of the enzyme for the hydrolysis of casein followed Michaelis-Menten kinetics with Km of 0.46 mg/mL. The purified enzyme was inhibited by the general serine protease inhibitor phenyl methyl sulphonyl fluoride (PMSF) and also by the specific trypsin inhibitor N-p-tosyl-L-lysine chloromethyl ketone (TLCK) using Nalpha-CBZ-L-lysine p-nitrophenyl ester hydrochloride (CBZ-Lys.pNP) as a substrate. The protease was inhibited by the following ions in decreasing order: Zn2+>Fe3+>Cu2+>Al3+>Co2+=Pb2+>Cd2+>Mn2+. The ions Li+, Na+, K+, Mg2+, and Ba2+ had little effect on the enzyme, and Ca2+ can partially promote its activity at low concentration.
Genotyping of Streptococcus agalactiae strains isolated from fish, human and cattle and their virulence potential in Nile tilapia.
Pereira UP, Mian GF, Oliveira IC, Benchetrit LC, Costa GM, Figueiredo HC.
Vet Microbiol. 2010 Jan 6;140(1-2):186-92. Epub 2009 Aug 8.
Streptococcus agalactiae (Lancefield group B; GBS) is a pathogen that causes meningoencephalitis in fish, mastitis in cows, and neonatal sepsis in humans. The objective of this study was to characterize S. agalactiae isolated from fish (n=27), cows (n=9), and humans (n=10) using pulsed-field gel electrophoresis (PFGE) and to investigate the virulence of the identified strains in Nile tilapia (Oreochromis niloticus). The PFGE types were determined by dendogram analyses and the in vivo virulence was evaluated by experimental infection (using i.p. and immersion routes) of Nile tilapia. Among the fish strains, 5 different PFGE patterns were observed and 21 strains showed the same genetic pattern. In some farms two or three profiles occurred simultaneously. The bovine and human strains exhibited high genetic diversity and few relationships were established among S. agalactiae strains from the three host origins analyzed. Eight S. agalactiae strains from fish caused high mortality of Nile tilapia. Three bovine strains infected Nile tilapia (by i.p. route) and two of those strains caused clinical signs of meningoencephalitis. All human strains (n=5) infected Nile tilapia (by i.p. route) and meningoencephalitis was induced by one strain (by both i.p. and immersion routes). In conclusion, the analyzed strains from the three natural hosts did not show genetic relatedness, yet some of the bovine and human strains were able to infect fish and cause meningoencephalitis. We suggest that genetic linkage is not a prerequisite for S. agalactiae to cross the host-specific barrier.
The B chromosomes of the African cichlid fish Haplochromis obliquidens harbor 18S rRNA gene copies.
Poletto AB, Ferreira IA, Martins C.
BMC Genet. 2010 Jan 5;11:1.
BACKGROUND: Diverse plant and animal species have B chromosomes, also known as accessory, extra or supernumerary chromosomes. Despite being widely distributed among different taxa, the genomic nature and genetic behavior of B chromosomes are still poorly understood. RESULTS: In this study we describe the occurrence of B chromosomes in the African cichlid fish Haplochromis obliquidens. One or two large B chromosome(s) occurring in 39.6% of the analyzed individuals (both male and female) were identified. To better characterize the karyotype and assess the nature of the B chromosomes, fluorescence in situ hybridization (FISH) was performed using probes for telomeric DNA repeats, 18S and 5S rRNA genes, SATA centromeric satellites, and bacterial artificial chromosomes (BACs) enriched in repeated DNA sequences. The B chromosomes are enriched in repeated DNAs, especially non-active 18S rRNA gene-like sequences. CONCLUSION: Our results suggest that the B chromosome could have originated from rDNA bearing subtelo/acrocentric A chromosomes through formation of an isochromosome, or by accumulation of repeated DNAs and rRNA gene-like sequences in a small proto-B chromosome derived from the A complement.
Effects of environmental hypoxia on cardiac energy metabolism and performance in tilapia.
Speers-Roesch B, Sandblom E, Lau GY, Farrell AP, Richards JG.
Am J Physiol Regul Integr Comp Physiol. 2010 Jan;298(1):R104-19. Epub 2009 Oct 28.
The ability of an animal to depress ATP turnover while maintaining metabolic energy balance is important for survival during hypoxia. In the present study, we investigated the responses of cardiac energy metabolism and performance in the hypoxia-tolerant tilapia (Oreochromis hybrid sp.) during exposure to environmental hypoxia. Exposure to graded hypoxia (> or =92% to 2.5% air saturation over 3.6 +/- 0.2 h) followed by exposure to 5% air saturation for 8 h caused a depression of whole animal oxygen consumption rate that was accompanied by parallel decreases in heart rate, cardiac output, and cardiac power output (CPO, analogous to ATP demand of the heart). These cardiac parameters remained depressed by 50-60% compared with normoxic values throughout the 8-h exposure. During a 24-h exposure to 5% air saturation, cardiac ATP concentration was unchanged compared with normoxia and anaerobic glycolysis contributed to ATP supply as evidenced by considerable accumulation of lactate in the heart and plasma. Reductions in the provision of aerobic substrates were apparent from a large and rapid (in <1 h) decrease in plasma nonesterified fatty acids concentration and a modest decrease in activity of pyruvate dehydrogenase. Depression of cardiac ATP demand via bradycardia and an associated decrease in CPO appears to be an integral component of hypoxia-induced metabolic rate depression in tilapia and likely contributes to hypoxic survival.
Individual and combined effects of heavy metals on serum biochemistry of Nile tilapia Oreochromis niloticus.
Firat O, Kargin F.
Arch Environ Contam Toxicol. 2010 Jan;58(1):151-7. Epub 2009 Jun 2.
Changes in serum biochemistry in response to single- and combined-metal exposure were studied in a freshwater fish Oreochromis niloticus. Fish were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn+1.0 mg/L Cd mixtures for 7 and 14 days to determine levels of biochemical parameters and metals in blood serum. The individual and combined effects of metals caused an increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and in levels of albumin, transferrin, ceruloplasmin, cortisol, glucose, and total protein, whereas they caused a decrease in cholesterol levels. At both exposure periods, increased ALT activity of fish exposed to Cd was higher compared with the Zn and Zn+Cd groups, respectively. The decreased cholesterol level was higher in the Cd alone, and for Cd in combination with Zn, than in Zn alone at 14 days. Zn or Cd levels increased in the blood serum of fish exposed to metals individually or in combination. When fish were exposed to the mixtures of Zn+Cd, concentrations of these metals in their serum were lower than in fish exposed to individual metals. One metal blocks or even antagonizes the gill epithelium absorption of the other and thereby limits the distribution of the metal in blood. The results indicate that biochemical parameters in fish blood can be used as an indicator of heavy-metal toxicity.
Effect of cortisol on melatonin production by the pineal organ of tilapia, Oreochromis mossambicus.
Nikaido Y, Aluru N, McGuire A, Park YJ, Vijayan MM, Takemura A.
Comp Biochem Physiol A Mol Integr Physiol. 2010 Jan;155(1):84-90. Epub 2009 Oct 15.
The aim of the present study was to examine the involvement of cortisol on melatonin synthesis in the pineal organ of the Mozambique tilapia, Oreochromis mossambicus. The circulating levels of melatonin in this species exhibited daily variations with a decrease during the photophase (0600, 1200, and 1800 h) and an increase during the scotophase (0000 h), while cortisol levels peaked during the early photophase (0600 h). The pineal organ was cultured in vitro in the dark in the presence of cortisol mimicking either stressed (100 ng/mL) or resting (10 ng/mL) concentration in tilapia. High cortisol concentration significantly reduced the levels of melatonin secreted into the medium. In the fish reared under stressful conditions, the nocturnal circulating levels of cortisol increased significantly, while melatonin did not change significantly. We detected glucocorticoid receptor (GR) transcripts in the pineal organ and a quantitative real-time PCR revealed that this receptor mRNA abundance fluctuated diurnally, increasing at 0600, 1800, and 0000 h and decreasing at 1200 h. The GR mRNA abundance in the pineal organ was not altered either in vitro when the organ was cultured in the presence of 100 ng/mL cortisol or in vivo when the fish were reared under stressful conditions. On the basis of these findings, it is proposed that cortisol lowers melatonin synthesis in the pineal organ, while the role of GR signaling in this process remains to be established.
Genotoxicity of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus.
Osman A, Ali E, Hashem M, Mostafa M, Mekkawy I.
Ecotoxicol Environ Saf. 2010 Jan;73(1):24-31. Epub 2009 Oct 6.
In the present work we have described the genotoxic potential of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus for the first time by three complementary tests: micronucleus test (MN), nuclear lesions (NL) and comet assay (CA). The groups exposed to the zoosporic fungi subjected to the MN and NL test showed statistically significant differences in MN and NL frequencies with respect to the control one. Also, a significant increase (p<0.001) in micronuclei and nuclear lesions frequencies were recorded with the increase in exposure time. A correlation was observed between the frequencies of MN and NL, suggesting the importance for recording this anomaly in order to improve the information obtained with the MN test. Therefore, our results suggest that the nuclear lesions found here should be considered indicators of genotoxicity, in addition to the typical micronuclei forms. The result of the comet assay showed a significant difference in the percentages of the damaged DNA in the comet tail (%TDNA) of the treated groups comparing to the control. A significant (p<0.001) increase in the DNA damage of the treated groups with the increase in exposure time was recorded, confirming the results of the MN and the NL tests. The results of the current study will be useful for future work involving the biomonitoring of regions where Nile tilapia survive. These data allow us to consider O. niloticus niloticus as a good bioindicator of the effects of genotoxic agents that might be present in the aquatic habitat.
Ça faisait longtemps que je ne l’avais pas fait. C’est l’occasion ou jamais. Au programme : des Midas, de la phylogénie, l’évolution du cerveau (ou pourquoi les pétricoles pensent pas comme les sabulicoles), des tilapias qui voient violet, de la génomique (ça je suis à peu près sûr que personne demandera le papier, et d’ailleurs vous êtes combien à savoir ce qu’est la génomique ???), des femelles incubantes en hypoxie, des mâles dominants qui auraient une meilleure audition, encore de la vision (là j’y comprends pas grand-chose…), des tilapia qui ont chopé l’herpès (enfin un virus qui ressemble à ça pour être exact), comment rendre vos cichlidés plus intelligents, de la génétique de discus (non c’est pas ce que vous croyez), de la phylogénie de Tropheus (non, svp sortez pas de bazooka), de la plasticité phénotypique de la vision (ben oui maintenir les poissons dans le noir, ça leur fait de l’effet), comment rendre vos cichlidés moins agressifs en jouant avec la lumière (ca marche au moins sur vos dimerus si vous en avez), que se passe-t-il dans la tête d’un mâle en pleine ascension sociale, de la phylogénie de vers parasites (qui n’intéressera personne ici…), de la génétique de la coloration des haplos du Victoria (ou pourquoi celui là il est jaune et l’autre il est rouge), le constat que nos cichlidés tapent plus facilement sur les dominants des autres espèces que sur les dominés, des hormones de burtoni (qui n’intéresseront personne…), du stress chez des tilapia (qui n’intéressera encore une fois personne), du sexe des tilapias (non ça parle encore de génétique…), de la viabilité des hybrides et de la divergence entre espèces (ça, ça devrait en intéresser beaucoup, quoique…), de la mobilité spermatique des burtoni, des récepteurs d’oestrogènes de tilapia, de l’évolution génomique des midas (qui malheureusement intéressera pas grand monde), de la coloration des midas (oui encore eux), des préférences sexuelles chez les Nyassachromis, encore des gènes opsin, du constat que les nigro explorateurs réagissent moins vite face à un prédateur (je suis curieux de voir leur robot lol, faut que je trouve l’article !), des mangeurs d’écailles asymétriques, de l’introgression entre zebra et fuelleborni, de la biogéographie de Cichla, encore de la vision de cichlidé, de la toxicologie (suis pas fan, mais bon…), de la détermination du sexe chez les cichlidés du Malawi, des cellules intestinales de poisson, de la morphométrie de Tropheus (avec des femelles à grosse bouche), encore du stress chez les tilapia (ils ont pas de bol !), un peu de biologie cellulaire, des enzymes de tilapia, des chromosomes B au Victoria, encore du stress chez les tilapias (à croire que les mecs sont des sadiques qui adorent asphyxier leurs poissons !), et après ça, d’autres vont les intoxiquer aux métaux lourds (sadiques je vous dis !), encore des hormones de tilapia, après ça, ils leur refilent des champignons pathogènes, encore des enzymes de tilapia, de la différenciation du sexe de tilapia en boîte de pétri, des tilapias qui sentent les odeurs des poissons rouges, de la génétique des populations de Pseudocrenilabrus, des variations du niveau du lac Malawi et de l’expansion des populations de pétricoles, et c’est tout pour la période de janvier 2010 à aujourd’hui (hors descriptions scientifiques).
Si vous voulez des pdf, faites moi signe, je dois avoir accès à la plupart d’entre eux. Et préparez une bonne dose d’aspirine !
Séb
Local variation and parallel evolution: morphological and genetic diversity across a species complex of neotropical crater lake cichlid fishes.
Philos Trans R Soc Lond B Biol Sci. 2010 Jun 12;365(1547):1763-82.
Elmer KR, Kusche H, Lehtonen TK, Meyer A.
The polychromatic and trophically polymorphic Midas cichlid fish species complex (Amphilophus cf. citrinellus) is an excellent model system for studying the mechanisms of speciation and patterns of phenotypic diversification in allopatry and in sympatry. Here, we first review research to date on the species complex and the geological history of its habitat. We analyse body shape variation from all currently described species in the complex, sampled from six crater lakes (maximally 1.2-23.9 kyr old) and both great lakes in Nicaragua. We find that Midas cichlid populations in each lake have their own characteristic body shape. In lakes with multiple sympatric species of Midas cichlid, each species has a distinct body shape. Across the species complex, most body shape change relates to body depth, head, snout and mouth shape and caudal peduncle length. There is independent parallel evolution of an elongate limnetic species in at least two crater lakes. Mitochondrial genetic diversity is higher in crater lakes with multiple species. Midas cichlid species richness increases with the size and age of the crater lakes, though no such relationship exists for the other syntopic fishes. We suggest that crater lake Midas cichlids follow the predicted pattern of an adaptive radiation, with early divergence of each crater lake colonization, followed by intralacustrine diversification and speciation by ecological adaptation and sexual selection.
Multilocus phylogeny and rapid radiations in Neotropical cichlid fishes (Perciformes: Cichlidae: Cichlinae).
Mol Phylogenet Evol. 2010 Jun;55(3):1070-86. Epub 2010 Feb 21.
López-Fernández H, Winemiller KO, Honeycutt RL.
Neotropical cichlid fishes comprise approximately 60 genera and at least 600 species, but despite this diversity, their phylogeny is only partially understood, which limits taxonomic, ecological and evolutionary research. We report the largest molecular phylogeny of Neotropical cichlids produced to date, combining data from three mitochondrial and two nuclear markers for 57 named genera and 154 species from South and Central America. Neotropical cichlids (subfamily Cichlinae) were strongly monophyletic and were grouped into two main clades in which the genera Retroculus (Tribe Retroculini) and Cichla (Cichlini) were sister to a monophyletic group containing all other lineages. This group included the tribes Chaetobranchini, Astronotini, Geophagini, Cichlasomatini and Heroini. Topological comparisons with previously published hypotheses indicated that our results are congruent with recent analyses of the tribe Cichlasomatini, but significantly more likely than published hypotheses for Geophagini, Heroini and the entire Cichlinae. Improved resolution and support are attributed to increased taxon sampling and to the addition of taxa never before included in phylogenetic analyses. Geophagini included two major subclades congruent with our own previous findings but more strongly supported; we also found a new and strongly supported sister-group relationship between Guianacara and Mazarunia. Cichlasomatini relationships were similar to recently proposed topologies, but contrastingly, we found a monophyletic Cichlasoma and support for a monophyletic grouping of the Aequidens diadema and A. tetramerus groups. Three basal South American Heroini lineages were recovered: (Hypselecara+Hoplarchus), Pterophyllum, and a grouping we refer to as mesonautines. Three other South American clades, caquetaines, Australoheros and the 'Cichlasoma'festae group, were nested within Central American clades. Most Heroini diversity was divided into two relatively well-supported large groups: the Southern Central American Clade, including clades herein referred to as nandopsines, caquetaines and amphilophines, and the Northern Central American Clade, including astatheroines, tomocichlines and herichthyines. Some of these groups have been previously identified, but often with different taxonomic compositions. Further resolution of Neotropical cichlid relationships, especially within the large amphilophine clade of Heroini, will require additional phylogenetic analysis. Nevertheless, the topology from this study provides a robust phylogenetic framework for studying evolutionary diversification in Neotropical cichlids. Significantly-short branches at the base of Geophagini and Heroini are compatible with early bursts of divergence that are characteristic of adaptive radiations. This pattern suggests diversification of Neotropical cichlid genera occurred rapidly, with subsequent convergent, adaptive ecomorphological diversification among and within South and Central American clades. 2010 Elsevier Inc. All rights reserved.
Brain diversity evolves via differences in patterning.
Proc Natl Acad Sci U S A. 2010 May 3. [Epub ahead of print]
Sylvester JB, Rich CA, Loh YH, van Staaden MJ, Fraser GJ, Streelman JT.
Differences in brain region size among species are thought to arise late in development via adaptive control over neurogenesis, as cells of previously patterned compartments proliferate, die, and/or differentiate into neurons. Here we investigate comparative brain development in ecologically distinct cichlid fishes from Lake Malawi and demonstrate that brains vary among recently evolved lineages because of early patterning. Divergence among rock-dwellers and sand-dwellers in the relative size of the telencephalon versus the thalamus is correlated with gene expression variation in a regulatory circuit (composed of six3, fezf2, shh, irx1b, and wnt1) known from model organisms to specify anterior-posterior (AP) brain polarity and position the shh-positive signaling boundary zona limitans intrathalamica (ZLI) in the forebrain. To confirm that changes in this coexpression network are sufficient to produce the differences we observe, we manipulated WNT signaling in vivo by treating rock-dwelling cichlid embryos with temporally precise doses of LiCl. Chemically treated rock-dwellers develop gene expression patterns, ZLIs, and forebrains distinct from controls and untreated conspecifics, but strongly resembling those of sand-dwellers. Notably, endemic Malawi rock- and sand-dwelling lineages are alternately fixed for an SNP in irx1b, a mediator of WNT signaling required for proper thalamus and ZLI. Together, these natural experiments in neuroanatomy, development, and genomics suggest that evolutionary changes in AP patterning establish ecologically relevant differences in the elaboration of cichlid forebrain compartments. In general, variation in developmental patterning might lay the foundations on which neurogenesis erects diverse brain architectures.
Electrophysiological assessment of spectral sensitivity in adult Nile tilapia Oreochromis niloticus: evidence for violet sensitivity.
Lisney TJ, Studd E, Hawryshyn CW.
J Exp Biol. 2010 May;213(Pt 9):1453-63.
The cichlid fish radiations of the African Great Lakes are an important model for evolutionary biology. Cichlids have diverse colour vision systems and predominately express three cone visual pigments. However, rare populations of spectrally distinct cones have been found in a number of species, but it is not known whether they contribute to spectral sensitivity. Adult Nile tilapia, Oreochromis niloticus, an ancestral outgroup to the cichlid radiations in the Great Lakes, have three cone types: short-wavelength sensitive (SWS), medium-wavelength sensitive (MWS) and long-wavelength sensitive (LWS) cones, but evidence from microspectrophotometry and cone opsin gene expression suggests they may also have violet-sensitive (VS) cones. We used electrophysiology to assess spectral sensitivity in this species and found evidence of four sensitivity peaks in the ranges 380-420, 440-480, 500-600 and 600-680 nm, with maximal sensitivity at longer wavelengths. The continued presence of a 380-420 nm peak under long-wavelength chromatic adapting backgrounds indicates that this is due to a VS cone mechanism not the beta-band of the LWS cone mechanism. Differences in spectral sensitivity curves recorded at different times of year revealed evidence of A1/A2 shifts. The presence of notches in the sensitivity curves and a multiple-mechanisms model used to assess cone contributions indicated that the curves are the result of four cone mechanisms (VS, SWS, MWS and LWS cones) and that chromatically opponent processes occur between mechanisms. The spectral transmittance of the lens steeply declines between 410-380 nm, limiting the short-wavelength limb of the VS cone. As adults, Nile tilapia appear to possess the necessary retinal mechanisms for colour vision. While maximal sensitivity to longer wavelengths is an adaptation to the wavelengths of light predominantly available in their natural habitats, their broad sensitivity range suggests that Nile tilapia possess a flexible, generalised visual system able to adapt to changes in visual environment in their highly variable natural habitat.
Energetics of hypoxia in a mouth-brooding cichlid: evidence for interdemic and developmental effects.
Reardon EE, Chapman LJ.
Physiol Biochem Zool. 2010 May-Jun;83(3):414-23.
We used a common-garden rearing experiment to explore environmentally induced tolerance to hypoxia in the African mouth-brooding cichlid Pseudocrenilabrus multicolor. F(1) fish originating from three field populations were grown under low or high dissolved oxygen (DO), and their resting routine metabolic rate (RMR), critical oxygen tension (P(crit)), and marginal metabolic scope (MMS) were quantified. In a second rearing experiment, we compared the RMR of brooding and nonbrooding females of low-DO origin grown under low and high DO. Fish reared under low DO had a lower P(crit) than fish reared under high DO. There was also an interaction between treatment and gender; females had a higher P(crit) than males when reared under normoxia. Variation in RMR was driven primarily by population effects, and there was an interaction between treatment and population. Regardless of population or treatment, males had a higher MMS than females. Fish reared under low DO had a higher MMS than fish reared under high DO, except for the high-DO population in which there was no treatment effect. Brooding females had a higher RMR than postbrooding females regardless of the growth treatment, indicating an energetic cost to brooding. The results suggest a strong element of developmental plasticity in P(crit) across populations and both plastic and genetic components of variation in the RMR and MMS. This study also highlights the cost of parental care in mouth-brooding fishes, which may increase the fitness of the offspring at the energetic expense of the parent, a cost that may be elevated under hypoxia.
An EST resource for tilapia based on 17 normalized libraries and assembly of 116,899 sequence tags.
Lee BY, Howe AE, Conte MA, D'Cotta H, Pepey E, Baroiller JF, di Palma F, Carleton, KL, Kocher TD.
BMC Genomics. 2010 Apr 30;11(1):278. [Epub ahead of print]
ABSTRACT: BACKGROUND: Large collections of expressed sequence tags (ESTs) are a fundamental resource for analysis of gene expression and annotation of genome sequences. We generated 116,899 ESTs from 17 normalized and two non-normalized cDNA libraries representing 16 tissues from tilapia, a cichlid fish widely used in aquaculture and biological research. RESULTS: The ESTs were assembled into 20,190 contigs and 36,028 singletons for a total of 56,218 unique sequences and a total assembled length of 35,168,415bp. Over the whole project, a unique sequence was discovered for every 2.079 sequence reads. 17,722 (31.5%) of these unique sequences had significant BLAST hits (e-value <10> 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.
Testing the carotenoid trade-off hypothesis in the polychromatic Midas cichlid, Amphilophus citrinellus.
Lin SM, Nieves-Puigdoller K, Brown AC, McGraw KJ, Clotfelter ED.
Physiol Biochem Zool. 2010 Mar-Apr;83(2):333-42.
Many animals use carotenoid pigments derived from their diet for coloration and immunity. The carotenoid trade-off hypothesis predicts that, under conditions of carotenoid scarcity, individuals may be forced to allocate limited carotenoids to either coloration or immunity. In polychromatic species, the pattern of allocation may differ among individuals. We tested the carotenoid trade-off hypothesis in the Midas cichlid, Amphilophus citrinellus, a species with two ontogenetic color morphs, barred and gold, the latter of which is the result of carotenoid expression. We performed a diet-supplementation experiment in which cichlids of both color morphs were assigned to one of two diet treatments that differed only in carotenoid content (beta-carotene, lutein, and zeaxanthin). We measured integument color using spectrometry, quantified carotenoid concentrations in tissue and plasma, and assessed innate immunity using lysozyme activity and alternative complement pathway assays. In both color morphs, dietary carotenoid supplementation elevated plasma carotenoid circulation but failed to affect skin coloration. Consistent with observable differences in integument coloration, we found that gold fish sequestered more carotenoids in skin tissue than barred fish, but barred fish had higher concentrations of carotenoids in plasma than gold fish. Neither measure of innate immunity differed between gold and barred fish, or as a function of dietary carotenoid supplementation. Lysozyme activity, but not complement activity, was strongly affected by body condition. Our data show that a diet low in carotenoids is sufficient to maintain both coloration and innate immunity in Midas cichlids. Our data also suggest that the developmental transition from the barred to gold morph is not accompanied by a decrease in innate immunity in this species.
SEQUENTIAL FEMALE ASSESSMENT DRIVES COMPLEX SEXUAL SELECTION ON BOWER SHAPE IN A CICHLID FISH.
Young KA, Genner MJ, Haesler MP, Joyce DA.
Evolution. 2010 Feb 26. [Epub ahead of print]
In many animals, sexual selection on male traits results from female mate choice decisions made during a sequence of courtship behaviors. We use a bower-building cichlid fish, Nyassachromis cf. microcephalus, to show how applying standard selection analysis to data on sequential female assessment provides new insights into sexual selection by mate choice. We first show that the cumulative selection differentials confirm previous results suggesting female choice favors males holding large volcano-shaped sand bowers. The sequential assessment analysis reveals these cumulative differentials are the result of selection acting on different bower dimensions during the courtship sequence; females choose to follow males courting from tall bowers, but choose to engage in premating circling with males holding bowers with large diameter platforms. The approach we present extends standard selection analysis by partitioning the variances of increasingly accurate estimates of male reproductive fitness and is applicable to systems in which sequential female assessment drives sexual selection on male traits.
Scale-eating cichlids: from hand(ed) to mouth.
Palmer AR.
J Biol. 2010 Feb 24;9(2):11. [Epub ahead of print]
ABSTRACT: Two recent studies in BMC Biology and Evolution raise important questions about a textbook case of frequency-dependent selection in scale-eating cichlid fishes. They also suggest a fascinating new line of research testing the effects of handed behavior on morphological asymmetry.
Genetic basis of differential opsin gene expression in cichlid fishes.
Carleton KL, Hofmann CM, Klisz C, Patel Z, Chircus LM, Simenauer LH, Soodoo N,Albertson RC, Ser JR.
J Evol Biol. 2010 Feb 23. [Epub ahead of print]
Abstract Visual sensitivity can be tuned by differential expression of opsin genes. Among African cichlid fishes, seven cone opsin genes are expressed in different combinations to produce diverse visual sensitivities. To determine the genetic architecture controlling these adaptive differences, we analysed genetic crosses between species expressing different complements of opsin genes. Quantitative genetic analyses suggest that expression is controlled by only a few loci with correlations among some genes. Genetic mapping identifies clear evidence of trans-acting factors in two chromosomal regions that contribute to differences in opsin expression as well as one cis-regulatory region. Therefore, both cis and trans regulation are important. The simple genetic architecture suggested by these results may explain why opsin gene expression is evolutionarily labile, and why similar patterns of expression have evolved repeatedly in different lineages.
Are fast explorers slow reactors? Linking personality type and anti-predator behaviour.
Jones KA, Godin JG.
Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S
Response delays to predator attack may be adaptive, suggesting that latency to respond does not always reflect predator detection time, but can be a decision based on starvation-predation risk trade-offs. In birds, some anti-predator behaviours have been shown to be correlated with personality traits such as activity level and exploration. Here, we tested for a correlation between exploration behaviour and response latency time to a simulated fish predator attack in a fish species, juvenile convict cichlids (Amatitlania nigrofasciata). Individual focal fish were subjected to a standardized attack by a robotic fish predator while foraging, and separately given two repeated trials of exploration of a novel environment. We found a strong positive correlation between exploration and time taken to respond to the predator model. Fish that were fast to explore the novel environment were slower to respond to the predator. Our study therefore provides some of the first experimental evidence for a link between exploration behaviour and predator-escape behaviour. We suggest that different behavioural types may differ in how they partition their attention between foraging and anti-predator vigilance.
HANDEDNESS AND ASYMMETRY IN SCALE-EATING CICHLIDS: ANTISYMMETRIES OF DIFFERENT STRENGTH.
Van Dooren TJ, van Goor HA, van Putten M.
Evolution. 2010 Feb 19. [Epub ahead of print]
Individual symmetry is believed to be advantageous and reflecting developmental stability, but frequency-dependent selection can also maintain polymorphisms of asymmetric phenotypes. There are many examples of so-called antisymmetry, where mirror image morphs occur at equal frequencies. With very few exceptions, these are caused by nongenetic variation. One notable exception is handedness and mouth bending variation in the scale-eating cichlid Perissodus microlepis, which has been suggested to be an example of antisymmetry determined by a single genetic locus of large effect. Here, we report that this handedness and mouth bending asymmetry are not jointly and exclusively determined by a single major locus. We found no evidence of a major locus for asymmetry and some support for a major handedness locus. Also, asymmetry is plastic in this species: it can change in adults. We suggest that behavioral handedness in this system precedes and guides morphological asymmetry.
Geography disentangles introgression from ancestral polymorphism in Lake Malawi cichlids.
Mims MC, Darrin Hulsey C, Fitzpatrick BM, Todd Streelman J.
Mol Ecol. 2010 Feb 8. [Epub ahead of print]
Abstract Phenotypically diverse Lake Malawi cichlids exhibit similar genomes. The extensive sharing of genetic polymorphism among forms has both intrigued and frustrated biologists trying to understand the nature of diversity in this and other rapidly evolving systems. Shared polymorphism might result from hybridization and/or the retention of ancestrally polymorphic alleles. To examine these alternatives, we used new genomic tools to characterize genetic differentiation in widespread, geographically structured populations of Labeotropheus fuelleborni and Metriaclima zebra. These phenotypically distinct species share mitochondrial DNA (mtDNA) haplotypes and show greater mtDNA differentiation among localities than between species. However, Bayesian analysis of nuclear single nucleotide polymorphism (SNP) data revealed two distinct genetic clusters corresponding perfectly to morphologically diagnosed L. fuelleborni and M. zebra. This result is a function of the resolving power of the multi-locus dataset, not a conflict between nuclear and mitochondrial partitions. Locus-by-locus analysis showed that mtDNA differentiation between species (F(CT)) was nearly identical to the median single-locus SNP F(CT). Finally, we asked whether there is evidence for gene flow at sites of co-occurrence. We used simulations to generate a null distribution for the level of differentiation between co-occurring populations of L. fuelleborni and M. zebra expected if there was no hybridization. The null hypothesis was rejected for the SNP data; populations that co-occur at rock reef sites were slightly more similar than expected by chance, suggesting recent gene flow. The coupling of numerous independent markers with extensive geographic sampling and simulations utilized here provides a framework for assessing the prevalence of gene flow in recently diverged species.
The Casiquiare river acts as a corridor between the Amazonas and Orinoco river basins: biogeographic analysis of the genus Cichla.
Willis SC, Nunes M, Montaña CG, Farias IP, Ortí G, Lovejoy NR.
Mol Ecol. 2010 Feb 8. [Epub ahead of print]
Abstract The Casiquiare River is a unique biogeographic corridor between the Orinoco and Amazonas basins. We investigated the importance of this connection for Neotropical fishes using peacock cichlids (Cichla spp.) as a model system. We tested whether the Casiquiare provides a conduit for gene flow between contemporary populations, and investigated the origin of biogeographic distributions that span the Casiquiare. Using sequences from the mitochondrial control region of three focal species (C. temensis, C. monoculus, and C. orinocensis) whose distributions include the Amazonas, Orinoco, and Casiquiare, we constructed maximum likelihood phylograms of haplotypes and analyzed the populations under an isolation-with-migration coalescent model. Our analyses suggest that populations of all three species have experienced some degree of gene flow via the Casiquiare. We also generated a mitochondrial genealogy of all Cichla species using >2000 bp and performed a dispersal-vicariance analysis (DIVA) to reconstruct the historical biogeography of the genus. This analysis, when combined with the intraspecific results, supports two instances of dispersal from the Amazonas to the Orinoco. Thus, our results support the idea that the Casiquiare connection is important across temporal scales, facilitating both gene flow and the dispersal and range expansion of species.
The relationship between lens transmission and opsin gene expression in cichlids from Lake Malawi.
Hofmann CM, O'Quin KE, Justin Marshall N, Carleton KL.
Vision Res. 2010 Feb 8;50(3):357-63. Epub 2009 Dec 11.
The lens plays an important role in regulating the wavelengths of light that reach the retina. However, the evolutionary relationship between lens transmission and retinal sensitivity remains cloudy at best. We examined the relationship between lens transmission and opsin gene expression in a group of rapidly radiating cichlids from East Africa. Lens transmission was bimodal, either cutting off around 360 or 400 nm, and appeared to be quite labile evolutionarily. We found a strong correlation between lens transmission and SWS1 (UV) opsin gene expression, suggesting that UV transmitting lenses are adaptive in cichlids. Species which expressed high levels of SWS2B (violet) opsin varied in their lens transmission while most species that expressed high levels of SWS2A (blue) opsin had UV blocking lenses. In no instance did lens transmission appear to limit retinal sensitivity. Finally, the strong correlation that we observe between SWS1 expression and lens transmission suggests that these two traits might be coupled genetically. Copyright (c) 2009 Elsevier Ltd. All rights reserved.
Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS.
Wahidulla S, Rajamanickam YR.
Environ Sci Pollut Res Int. 2010 Feb;17(2):441-52. Epub 2009 Oct 2.
BACKGROUND, AIM, AND SCOPE: Mutagenic nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been known to arise in the environment through direct emissions from combustion sources and nitration of PAHs, primarily in the atmosphere. In the marine environment, PAHs are one of the classic anthropogenic organic pollutants, while nitrite (NO(2)(-)) is produced naturally via various biological processes like imbalance in nitrification/denitrification or eutrophication and subsequent oxygen depletion from an oversupply of nutrients. In this paper, we report the formation of PAH-DNA adducts in fish contaminated with PAHs and exposed to NO(2)(-) in the ambient water. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of the bile of the euryhaline fish Oreochromis mossambicus exposed simultaneously to field relevant sublethal concentrations of phenanthrene and NO(2)(-) and collision-induced dissociation of selected ions revealed the presence of DNA-PAH adducts. The present study indicates that, although several high sensitivity techniques have been developed for the analysis of PAH derived DNA adducts, MS/MS has emerged as a powerful tool in the detection and structure elucidation of DNA adducts. MATERIALS AND METHODS: Juvenile O. mossambicus from a local estuarine fish farm were used with increasing frequency for carcinogenicity testing and comparative cancer research. The fish were exposed to the alkylating agent phenanthrene in the presence of NO(2)(-). Composite untreated bile samples after dilution with methanol: water (1:1; v/v) were analyzed by ESI-MS. RESULTS: Several adducts could be evidenced in the bile by MS/MS. Deoxyadenosine/deoxyguanosine having a mass in the range of 450-650 amu is detected. In addition, a segment of modified dinucleotide with a mass that corresponds to a dimer consisting of a modified guanosine and a normal guanosine has also been identified in the bile. DISCUSSION: The formation of certain types of DNA adducts is a crucial step in the induction of cancer and a primary stage in mutagenesis. Phenanthrene injected by i.p. route led to the transformation of phenanthrene to N-formyl amino phenanthrene-N(6)-deoxyadenosine adduct, whereas the fish co-exposed to phenanthrene and ambient nitrite metabolizes PAH to mono-, di- as well as trinitro derivatives, which then react with DNA leading to the formation of mainly modified guanosine and adenosine adducts. In the present investigation, dinitrophenanthrene diol epoxide (DNPDE) adduct with guanosine (m/z 587) seems to be the dominant adduct in the mixture, and its presence is shown first as a comparatively less stable adduct, which decomposes to give a more stable N(2) adduct (m/z 567). CONCLUSIONS: MS/MS has proved to be useful in the rapid determination and discrimination of structurally different phenanthrene/derivatives DNA adducts in a complex mixture of fish bile co-exposed to phenanthrene and nitrite. However, the nature of metabolites formed is likely determined by the route of PAH administration, and there is a need to further define the early biochemical events of carcinogenesis in these species. RECOMMENDATIONS AND PERSPECTIVES: DNA adduct analysis in fish bile offers a promising approach to study the risk of potentiation of anthropogenic chemicals into genotoxic compounds in the presence of nitrite in the marine environment. We believe this is the first report on the formation of DNA-phenanthrene adducts on co-exposure of the fish to PAH and nitrite.
Multiple interacting Loci control sex determination in lake Malawi cichlid fish.
Ser JR, Roberts RB, Kocher TD.
Evolution. 2010 Feb 1;64(2):486-501. Epub 2009 Oct 23.
Several models have been proposed to suggest how the evolution of sex-determining mechanisms might contribute to speciation. Here, we describe the inheritance of sex in 19 fish species from the rapidly evolving flock of cichlids in Lake Malawi, Africa. We found that many of these species have a male heterogametic (XY) system on linkage group 7. Some species also segregate for a female heterogametic (ZW) system on linkage group 5 that is coincident with a dominant orange-blotch (OB) color pattern in females. The ZW system is epistatically dominant to the XY system when both are segregating within a family. Several lines of evidence suggest that additional sex-determining loci are segregating in some species. These results are consistent with the idea that genetic conflicts play an important role in the evolution of these species flocks and suggest that evolution of sex-determining mechanisms has contributed to the radiation of cichlid fish in East Africa.
Endosulfan increases seric interleukin-2 like (IL-2L) factor and immunoglobulin M (IgM) of Nile tilapia (Oreochromis niloticus) challenged with Aeromona hydrophila.
Tellez-Bañuelos MC, Santerre A, Casas-Solis J, Zaitseva G.
Fish Shellfish Immunol. 2010 Feb;28(2):401-5. Epub 2009 Nov 24.
Endosulfan is a persistent organochlorine insecticide which is extremely toxic to fish. It is known to induce immunological alterations in juvenile Nile tilapia (Oreochromis niloticus) such as increases in phagocytic activity and reactive oxygen species production of spleen macrophages. The purpose of the present study was to demonstrate the effects of acute exposure to a sublethal concentration of endosulfan (7 ppb, 96 h) on parameters of the adaptive humoral immune response of the aforementioned aquatic organism. The effect of endosulfan on the capacity of immune cells to produce interleukin-2 like (IL-2L) factor and immunoglobulin M (IgM) in response to a challenge with (1/2) LD50 of the infectious bacteria Aeromonas hydrophila was evaluated. Experimental results indicate that short, sublethal, endosulfan exposure triggers a succession of events beginning with non-specific activation of macrophages followed by an exacerbated synthesis of the IL-2L factor by activated B cells. This leads to significantly increased secretion of IgM and could in turn facilitate autoantibody production and the development of autoimmune pathologies. Copyright 2009 Elsevier Ltd. All rights reserved.
Effect of ferrous sulphate on aspartate and alanine aminotransferases of brain of Tilapia mossambica.
Nunes ES, Desai SN, Desai PV.
Food Chem Toxicol. 2010 Feb;48(2):490-4. Epub 2009 Nov 1.
Iron in the form of ferrous sulphate coming from sources such as mines, writing inks, blue pigments, dyeing industries, photography, medicine, deodorizers, disinfectants, fungicides and molluscides, etc. contributes in elevating ferrous sulphate of water bodies. The present study investigated the action of ferrous sulphate on the local fish Tilapia mossambica. Tilapia exposed to 0.001 g/L ferrous sulphate for 30 days showed reduction of cytosolic AST and ALT activities of cerebral cortex by 35.4% and 29.1%, respectively, while exposure to 0.01% ferrous sulphate promoted 49.2% and 38.4% reduction of AST and ALT activities. Similarly mitochondrial AST and ALT activities reduced by 50% and 34.8%, respectively, on exposure to 0.001 g/L ferrous sulphate while 0.01 g/L ferrous sulphate promoted 51% and 47.8% reductions of AST and ALT activities at the end of 30 days, suggesting interference in the glutamate and protein metabolism of Tilapia brain. Copyright 2009 Elsevier Ltd. All rights reserved.
Histochemical study on the intestine goblet cells in cichlid and poecilid species (Teleostei).
Leknes IL.
Tissue Cell. 2010 Feb;42(1):61-4. Epub 2009 Oct 14.
Histochemical properties of intestine goblet cells in firemouth cichlid, zebra mbuna, freshwater angelfish and platyfish are described. Goblet cells occurred regularly in the epithelial cell layer throughout the entire intestine, they were strongly coloured by alcian blue at pH 2.5. This colour got gradually weaker when the pH was reduced, but still after alcian blue at pH 0.2 these cells displayed a distinct blue colour. When the goblet cells were treated with periodic acid-Schiff (PAS), they displayed a strong purple-magenta colour. The findings that a number of goblet cells displayed various colours between blue and purple-magenta when acidic alcian blue was followed by PAS, and between blue and red-brown when acidic alcian blue was followed by neutral red, may reflect different ages or stages of development and differentiation for these cells. However, such results may also suggest a true cellular heterogeneity in the present population of goblet cells, reflecting that the intestine mucus layer has a number of roles in teleosts like lubrication, protection, immunological defence, digestion and absorption. In the ferritin injected specimens of firemouth cichlid and platyfish, a number of macrophage-like cells in intestine wall displayed Prussian blue precipitations in tissue treated with acid ferrocyanide, suggesting that these cells play a cleansing role in the intestinal wall. No ferritin uptake was seen in the intestine goblet cells and eosinophilic granule cells. Copyright 2009 Elsevier Ltd. All rights reserved.
Evolution of a unique predatory feeding apparatus: functional anatomy, development and a genetic locus for jaw laterality in Lake Tanganyika scale-eating cichlids.
Stewart TA, Albertson RC.
BMC Biol. 2010 Jan 26;8:8.
BACKGROUND: While bilaterality is a defining characteristic of triploblastic animals, several assemblages have managed to break this symmetry in order to exploit the adaptive peaks garnered through the lateralization of behaviour or morphology. One striking example of an evolved asymmetry in vertebrates comes from a group of scale-eating cichlid fishes from Lake Tanganyika. Members of the Perissodini tribe of cichlid fishes have evolved dental and craniofacial asymmetries in order to more effectively remove scales from the left or right flanks of prey. Here we examine the evolution and development of craniofacial morphology and laterality among Lake Tanganyika scale-eating cichlids. RESULTS: Using both geometric and traditional morphometric methods we found that the craniofacial evolution in the Perissodini involved discrete shifts in skeletal anatomy that reflect differences in habitat preference and predation strategies. Further, we show that the evolutionary history of the Perissodini is characterized by an accentuation of craniofacial laterality such that certain taxa show elaborate sided differences in craniofacial shape consistent with the sub-partitioning of function between sides of the head during attacks. Craniofacial laterality in the scale-eating specialist Perissodus microlepis was found to be evident early in development and exhibited a unimodal distribution, which is contrary to the adult condition where jaw laterality has been described as a discrete, bimodal antisymmetry. Finally, using linkage and association analyses we identified a conserved locus for jaw handedness that segregates among East African cichlids. CONCLUSIONS: We suggest that, during the evolution of the Perissodini, selection has accentuated a latent, genetically determined handedness of the craniofacial skeleton, enabling the evolution of jaw asymmetries in order to increase predation success. Continued work on the developmental genetic basis of laterality in the Perissodini will facilitate a better understanding of the evolution of this unique group of fishes, as well as of left-right axis determination among vertebrates in general.
Sexual dimorphism and population divergence in the Lake Tanganyika cichlid fish genus Tropheus.
Herler J, Kerschbaumer M, Mitteroecker P, Postl L, Sturmbauer C.
Front Zool. 2010 Jan 22;7:4.
ABSTRACT: BACKGROUND: With about 120 colour morphs currently assigned to six nominal species, the genus Tropheus is an ideal model to study evolutionary divergence of populations in allopatry. The morphology of Tropheus has been described as relatively static, but reproductive constraints are sexually dimorphic due to mouthbrooding in females. We analysed phenotypic variation in six populations of T. moorii and one population of T. polli using geometric morphometrics to assess morphological differences among sexes in relation to the differentiation of populations and species. RESULTS: The mean shapes differed significantly between sexes, populations, and species even though within-sex variation exceeded the divergence among populations. The first principal component of Procrustes shape coordinates revealed differences between populations and species in mouth position and ventral head shape. The second principal component reflected sex-specific shape differences, mainly comprising a relatively larger female viscerocranium and, in particular, a larger buccal area. While shape variation between populations and between sexes was primarily located in the cranial region, within-sex variation was relatively uniform across all landmarks. CONCLUSIONS: Deviations of the between-population and between-sex pattern of shape variation from that within sex indicate that the differences in head shape likely result from both adaptations to female mouthbrooding and population-specific foraging strategies.
Hyperosmotic shock adaptation by cortisol involves upregulation of branchial osmotic stress transcription factor 1 gene expression in Mozambique Tilapia.
McGuire A, Aluru N, Takemura A, Weil R, Wilson JM, Vijayan MM.
Gen Comp Endocrinol. 2010 Jan 15;165(2):321-9. Epub 2009 Aug 3.
The Mozambique tilapia (Oreochromis mossambicus) is a euryhaline species that does not survive direct seawater exposure. Cortisol is involved in re-establishing electrolyte homeostasis in seawater and is thought to play a role in allowing tilapia to cope with abrupt seawater exposure, but the mechanism(s) are far from clear. Recently, osmotic stress transcription factor 1 (OSTF1) was identified as a key signaling molecule involved in hyperosmotic stress adaptation in tilapia. Consequently, we tested the hypothesis that upregulation of OSTF1 expression by cortisol is a key response for hyperosmotic stress adaptation in tilapia. Fish were exposed to different salinities over a 24h period, while a major electrolyte disturbance and mortality was observed only with full-strength seawater exposure. Therefore, we administered cocoa butter implants of cortisol (50mg/kg) intraperitoneally to tilapia maintained in fresh water and after three days exposed these fish to full-strength seawater. There was 50% mortality in the control fish upon seawater exposure, but this was abolished by cortisol treatment. Abrupt seawater exposure did not affect plasma cortisol levels, while, as expected, exogenous administration of this steroid elevated plasma cortisol levels both in fresh water and seawater. Cortisol treatment significantly induced OSTF1 gene expression in fresh water tilapia, and also enhanced further the seawater-induced OSTF1 mRNA abundance. Plasma osmolality decreased, while gill Na(+)/K(+)-ATPase activity was suppressed in the cortisol group in seawater compared to the sham group. This corresponded with a significant reduction in gill ionocyte size and Na(+)/K(+)-ATPase activity and protein expression after seawater exposure. Cortisol did not modify liver metabolism, but significantly suppressed gill metabolic capacity in seawater. Overall, cortisol adapts tilapia to a hyperosmotic shock associated with abrupt seawater exposure. This involves upregulation of OSTF1 gene expression and a concomitant suppression of branchial metabolism in tilapia.
Cloning and molecular characterization of the glucose transporter 1 in tilapia (Oreochromis niloticus).
Hrytsenko O, Pohajdak B, Xu BY, Morrison C, van Tol B, Wright JR Jr.
Gen Comp Endocrinol. 2010 Jan 15;165(2):293-303. Epub 2009 Aug 3.
Facilitative glucose transporters (GLUTs) are responsible for passively transporting monosaccharides across the plasma membrane. We sequenced and characterized the Nile tilapia (Oreochromis niloticus) GLUT-1 (tGLUT-1) cDNA and genomic DNA. Using rapid amplification of the cDNA ends (RACE), two tGLUT-1 transcripts were detected differing in the length of the 3' untranslated region, 2851 and 4577 bp. Translated tGLUT-1 is a 490 amino acid product, which shares 74% homology with that of humans. Computer analysis of the amino acid sequence predicted 12 transmembrane domains, which are conserved in the GLUT-1 of various species. The tGLUT-1 gene spans more than 11 kb, and similar to the mammalian GLUT-1 genes has a 10 exon, 9 intron organization. Potential promoter regulatory elements have some similarity to those recorded for human, mouse, and rat GLUT-1 genes. Tissue expression studies revealed both GLUT-1 transcripts in liver, Brockmann bodies (BB), heart, small intestine, adipose tissue, white and red muscle, gill, spleen, pituitary gland, and brain. The highest level of expression was detected in tilapia heart, followed by BB, brain, and muscle. Protein based food and glucose had minor or no effects on the level of tGLUT-1 expression in most tissues. The tGLUT-1 mRNA level was significantly induced by glucose and food only in white muscle. Current results suggest that tGLUT-1 is similar to the GLUT-1 of other teleost species and mammals at the genomic, mRNA, and amino acid levels, supporting the concept that tGLUT-1 functions as a ubiquitous basal level glucose transporter.
Genetic variation and demographic history of the Haplochromis laparogramma group of Lake Victoria-An analysis based on SINEs and mitochondrial DNA.
Mzighani SI, Nikaido M, Takeda M, Seehausen O, Budeba YL, Ngatunga BP, Katunzi, EF, Aibara M, Mizoiri S, Sato T, Tachida H, Okada N.
Gene. 2010 Jan 15;450(1-2):39-47.
More than 500 endemic haplochromine cichlid species inhabit Lake Victoria. This striking species diversity is a classical example of recent explosive adaptive radiation thought to have happened within the last approximately 15,000 years. In this study, we examined the population structure and historical demography of 3 pelagic haplochromine cichlid species that resemble in morphology and have similar niche, Haplochromis (Yssichromis) laparogramma, Haplochromis (Y.) pyrrhocephalus, and Haplochromis (Y.) sp. "glaucocephalus". We investigated the sequences of the mitochondrial DNA control region and the insertion patterns of short interspersed elements (SINEs) of 759 individuals. We show that sympatric forms are genetically differentiated in 4 of 6 cases, but we also found apparent weakening of the genetic differentiation in areas with turbid water. We estimated the timings of population expansion and species divergence to coincide with the refilling of the lake at the Pleistocene/Holocene boundary. We also found that estimates can be altered significantly by the choice of the shape of the molecular clock. If we employ the nonlinear clock model of evolutionary rates in which the rates are higher towards the recent, the population expansion was dated at around the event of desiccation of the lake ca. 17,000 YBP. Thus, we succeeded in clarifying the species and population structure of closely related Lake Victoria cichlids and in showing the importance of applying appropriate clock calibrations in elucidating recent evolutionary events.
Purification and characterization of trypsin from the intestine of hybrid tilapia (Oreochromis niloticusxO.aureus).
Wang Q, Gao ZX, Zhang N, Shi Y, Xie XL, Chen QX.
J Agric Food Chem. 2010 Jan 13;58(1):655-9.
Trypsin from the intestine of hybrid tilapia (Oreochromis niloticus x O.aureus) was purified by the following techniques: acetone precipitation, ammonium sulfate fractionation, Sephacryl S-200 gel filtration, and DEAE-sephacel ion exchange chromatography. The purified enzyme was determined to be homogeneous by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate (SDS)-PAGE. The molecular weight was estimated as 22,000 Da. The optimum pH and temperature of the enzyme for the hydrolysis of casein were determined to be 9.0 and 60 degrees C, respectively. The enzyme was stable over a broad pH range from 7.0 to 12.0 at 30 degrees C, and the enzyme was inactive at temperatures above 50 degrees C. The behavior of the enzyme for the hydrolysis of casein followed Michaelis-Menten kinetics with Km of 0.46 mg/mL. The purified enzyme was inhibited by the general serine protease inhibitor phenyl methyl sulphonyl fluoride (PMSF) and also by the specific trypsin inhibitor N-p-tosyl-L-lysine chloromethyl ketone (TLCK) using Nalpha-CBZ-L-lysine p-nitrophenyl ester hydrochloride (CBZ-Lys.pNP) as a substrate. The protease was inhibited by the following ions in decreasing order: Zn2+>Fe3+>Cu2+>Al3+>Co2+=Pb2+>Cd2+>Mn2+. The ions Li+, Na+, K+, Mg2+, and Ba2+ had little effect on the enzyme, and Ca2+ can partially promote its activity at low concentration.
Genotyping of Streptococcus agalactiae strains isolated from fish, human and cattle and their virulence potential in Nile tilapia.
Pereira UP, Mian GF, Oliveira IC, Benchetrit LC, Costa GM, Figueiredo HC.
Vet Microbiol. 2010 Jan 6;140(1-2):186-92. Epub 2009 Aug 8.
Streptococcus agalactiae (Lancefield group B; GBS) is a pathogen that causes meningoencephalitis in fish, mastitis in cows, and neonatal sepsis in humans. The objective of this study was to characterize S. agalactiae isolated from fish (n=27), cows (n=9), and humans (n=10) using pulsed-field gel electrophoresis (PFGE) and to investigate the virulence of the identified strains in Nile tilapia (Oreochromis niloticus). The PFGE types were determined by dendogram analyses and the in vivo virulence was evaluated by experimental infection (using i.p. and immersion routes) of Nile tilapia. Among the fish strains, 5 different PFGE patterns were observed and 21 strains showed the same genetic pattern. In some farms two or three profiles occurred simultaneously. The bovine and human strains exhibited high genetic diversity and few relationships were established among S. agalactiae strains from the three host origins analyzed. Eight S. agalactiae strains from fish caused high mortality of Nile tilapia. Three bovine strains infected Nile tilapia (by i.p. route) and two of those strains caused clinical signs of meningoencephalitis. All human strains (n=5) infected Nile tilapia (by i.p. route) and meningoencephalitis was induced by one strain (by both i.p. and immersion routes). In conclusion, the analyzed strains from the three natural hosts did not show genetic relatedness, yet some of the bovine and human strains were able to infect fish and cause meningoencephalitis. We suggest that genetic linkage is not a prerequisite for S. agalactiae to cross the host-specific barrier.
The B chromosomes of the African cichlid fish Haplochromis obliquidens harbor 18S rRNA gene copies.
Poletto AB, Ferreira IA, Martins C.
BMC Genet. 2010 Jan 5;11:1.
BACKGROUND: Diverse plant and animal species have B chromosomes, also known as accessory, extra or supernumerary chromosomes. Despite being widely distributed among different taxa, the genomic nature and genetic behavior of B chromosomes are still poorly understood. RESULTS: In this study we describe the occurrence of B chromosomes in the African cichlid fish Haplochromis obliquidens. One or two large B chromosome(s) occurring in 39.6% of the analyzed individuals (both male and female) were identified. To better characterize the karyotype and assess the nature of the B chromosomes, fluorescence in situ hybridization (FISH) was performed using probes for telomeric DNA repeats, 18S and 5S rRNA genes, SATA centromeric satellites, and bacterial artificial chromosomes (BACs) enriched in repeated DNA sequences. The B chromosomes are enriched in repeated DNAs, especially non-active 18S rRNA gene-like sequences. CONCLUSION: Our results suggest that the B chromosome could have originated from rDNA bearing subtelo/acrocentric A chromosomes through formation of an isochromosome, or by accumulation of repeated DNAs and rRNA gene-like sequences in a small proto-B chromosome derived from the A complement.
Effects of environmental hypoxia on cardiac energy metabolism and performance in tilapia.
Speers-Roesch B, Sandblom E, Lau GY, Farrell AP, Richards JG.
Am J Physiol Regul Integr Comp Physiol. 2010 Jan;298(1):R104-19. Epub 2009 Oct 28.
The ability of an animal to depress ATP turnover while maintaining metabolic energy balance is important for survival during hypoxia. In the present study, we investigated the responses of cardiac energy metabolism and performance in the hypoxia-tolerant tilapia (Oreochromis hybrid sp.) during exposure to environmental hypoxia. Exposure to graded hypoxia (> or =92% to 2.5% air saturation over 3.6 +/- 0.2 h) followed by exposure to 5% air saturation for 8 h caused a depression of whole animal oxygen consumption rate that was accompanied by parallel decreases in heart rate, cardiac output, and cardiac power output (CPO, analogous to ATP demand of the heart). These cardiac parameters remained depressed by 50-60% compared with normoxic values throughout the 8-h exposure. During a 24-h exposure to 5% air saturation, cardiac ATP concentration was unchanged compared with normoxia and anaerobic glycolysis contributed to ATP supply as evidenced by considerable accumulation of lactate in the heart and plasma. Reductions in the provision of aerobic substrates were apparent from a large and rapid (in <1 h) decrease in plasma nonesterified fatty acids concentration and a modest decrease in activity of pyruvate dehydrogenase. Depression of cardiac ATP demand via bradycardia and an associated decrease in CPO appears to be an integral component of hypoxia-induced metabolic rate depression in tilapia and likely contributes to hypoxic survival.
Individual and combined effects of heavy metals on serum biochemistry of Nile tilapia Oreochromis niloticus.
Firat O, Kargin F.
Arch Environ Contam Toxicol. 2010 Jan;58(1):151-7. Epub 2009 Jun 2.
Changes in serum biochemistry in response to single- and combined-metal exposure were studied in a freshwater fish Oreochromis niloticus. Fish were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn+1.0 mg/L Cd mixtures for 7 and 14 days to determine levels of biochemical parameters and metals in blood serum. The individual and combined effects of metals caused an increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and in levels of albumin, transferrin, ceruloplasmin, cortisol, glucose, and total protein, whereas they caused a decrease in cholesterol levels. At both exposure periods, increased ALT activity of fish exposed to Cd was higher compared with the Zn and Zn+Cd groups, respectively. The decreased cholesterol level was higher in the Cd alone, and for Cd in combination with Zn, than in Zn alone at 14 days. Zn or Cd levels increased in the blood serum of fish exposed to metals individually or in combination. When fish were exposed to the mixtures of Zn+Cd, concentrations of these metals in their serum were lower than in fish exposed to individual metals. One metal blocks or even antagonizes the gill epithelium absorption of the other and thereby limits the distribution of the metal in blood. The results indicate that biochemical parameters in fish blood can be used as an indicator of heavy-metal toxicity.
Effect of cortisol on melatonin production by the pineal organ of tilapia, Oreochromis mossambicus.
Nikaido Y, Aluru N, McGuire A, Park YJ, Vijayan MM, Takemura A.
Comp Biochem Physiol A Mol Integr Physiol. 2010 Jan;155(1):84-90. Epub 2009 Oct 15.
The aim of the present study was to examine the involvement of cortisol on melatonin synthesis in the pineal organ of the Mozambique tilapia, Oreochromis mossambicus. The circulating levels of melatonin in this species exhibited daily variations with a decrease during the photophase (0600, 1200, and 1800 h) and an increase during the scotophase (0000 h), while cortisol levels peaked during the early photophase (0600 h). The pineal organ was cultured in vitro in the dark in the presence of cortisol mimicking either stressed (100 ng/mL) or resting (10 ng/mL) concentration in tilapia. High cortisol concentration significantly reduced the levels of melatonin secreted into the medium. In the fish reared under stressful conditions, the nocturnal circulating levels of cortisol increased significantly, while melatonin did not change significantly. We detected glucocorticoid receptor (GR) transcripts in the pineal organ and a quantitative real-time PCR revealed that this receptor mRNA abundance fluctuated diurnally, increasing at 0600, 1800, and 0000 h and decreasing at 1200 h. The GR mRNA abundance in the pineal organ was not altered either in vitro when the organ was cultured in the presence of 100 ng/mL cortisol or in vivo when the fish were reared under stressful conditions. On the basis of these findings, it is proposed that cortisol lowers melatonin synthesis in the pineal organ, while the role of GR signaling in this process remains to be established.
Genotoxicity of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus.
Osman A, Ali E, Hashem M, Mostafa M, Mekkawy I.
Ecotoxicol Environ Saf. 2010 Jan;73(1):24-31. Epub 2009 Oct 6.
In the present work we have described the genotoxic potential of two pathogenic strains of zoosporic fungi (Achlya klebsiana and Aphanomyces laevis) on erythrocytes of Nile tilapia Oreochromis niloticus niloticus for the first time by three complementary tests: micronucleus test (MN), nuclear lesions (NL) and comet assay (CA). The groups exposed to the zoosporic fungi subjected to the MN and NL test showed statistically significant differences in MN and NL frequencies with respect to the control one. Also, a significant increase (p<0.001) in micronuclei and nuclear lesions frequencies were recorded with the increase in exposure time. A correlation was observed between the frequencies of MN and NL, suggesting the importance for recording this anomaly in order to improve the information obtained with the MN test. Therefore, our results suggest that the nuclear lesions found here should be considered indicators of genotoxicity, in addition to the typical micronuclei forms. The result of the comet assay showed a significant difference in the percentages of the damaged DNA in the comet tail (%TDNA) of the treated groups comparing to the control. A significant (p<0.001) increase in the DNA damage of the treated groups with the increase in exposure time was recorded, confirming the results of the MN and the NL tests. The results of the current study will be useful for future work involving the biomonitoring of regions where Nile tilapia survive. These data allow us to consider O. niloticus niloticus as a good bioindicator of the effects of genotoxic agents that might be present in the aquatic habitat.
Modifié en dernier par Séb_59 le 08 mai 2010 15:28, modifié 1 fois.
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