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328 results for “cichlid fish”
Fig. 2 in Water temperature affects aggressive interactions in a Neotropical cichlid fish
Fig. 2. Mean ± SE of initial (third day) and final (eighth day) frequencies of a. restrained aggression and b. overt aggression of isolated fish against the mirror for Cichlasoma paranaense. Different letters show differences among treatments. Mixed Model ANOVA completed by Fisher-LSD post hoc test.
Fig. 1 in Water temperature affects aggressive interactions in a Neotropical cichlid fish
Fig. 1. Mean ± SE of initial (third day) and final (eighth day) latency of swimming activity of isolated fish Cichlasoma paranaense. Different letters indicate statistical significance among treatments. Mixed Model ANOVA completed by Fisher-LSD post hoc test.
Data from: Lateralized feeding behavior is associated with asymmetrical neuroanatomy and lateralized gene expressions in the brain in scale-eating cichlid fish
Lateralized behavior ('handedness') is unusual, but consistently found across diverse animal lineages, including humans. It is thought to reflect brain anatomical and/or functional asymmetries, but its neuro-molecular mechanisms remain largely unknown. Lake Tanganyika scale-eating cichlid fish, Perissodus microlepis show pronounced asymmetry in their jaw morphology as well as handedness in feeding behavior – feeding scales preferentially only from one or the other side of their victims. This makes them an ideal model in which to investigate potential laterality in neuroanatomy and transcription in the brain in relation to behavioral handedness. After determining behavioral handedness in P. microlepis (preferred attack side), we estimated the volume of the hemispheres of brain regions and captured their gene expression profiles. Our analyses revealed that the degree of behavioral handedness is mirrored at the level of neuroanatomical asymmetry, particularly in the tectum opticum. Transcriptome analyses showed that different brain regions (tectum opticum, telencephalon, hypothalamus and cerebellum) display distinct expression patterns, potentially reflecting their developmental interrelationships. For numerous genes in each brain region, their extent of expression differences between hemispheres was found to be correlated with the degree of behavioral lateralization. Interestingly, the tectum opticum and telencephalon showed divergent biases on the direction of up- or down-regulation of the laterality candidate genes (e.g., grm2) in the hemispheres, highlighting the connection of handedness with gene expression profiles and the different roles of these brain regions. Hence, handedness in predation behavior may be caused by asymmetric size of brain hemispheres and also by lateralized gene expressions in the brain.
Data from: Species-specific differences in adaptive phenotypic plasticity in an ecologically relevant trophic trait: hypertrophic lips in Midas cichlid fishes
The spectacular species richness of cichlids and their diversity in morphology, coloration, and behaviour have made them an ideal model for the study of speciation and adaptive evolution. Hypertrophic lips evolved repeatedly and independently in African and Neotropical cichlid radiations. Cichlids with hypertrophic lips forage predominantly in rocky crevices and it has been hypothesized that mechanical stress caused by friction could result in larger lips through phenotypic plasticity. To test the influence of the environment on the size and development of lips, we conducted a series of breeding and feeding experiments on Midas cichlids. Full-sibs of Amphilophus labiatus (thick-lipped) and A. citrinellus (thin-lipped) each were split into a control group which was fed food from the water column and a treatment group whose food was fixed to substrates. We found strong evidence for phenotypic plasticity on lip area in the thick-lipped species, but not in the thin-lipped species. Intermediate phenotypic values were observed in hybrids from thick- and thin-lipped species reared under "control" conditions. Thus, both a genetic, but also a phenotypic plastic component is involved in the development of hypertrophic lips in Neotropical cichlids. Moreover, species-specific adaptive phenotypic plasticity was found, suggesting that plasticity is selected for in recent thick-lipped species.
Data from: Genomic signatures of divergent selection and speciation patterns in a 'natural experiment', the young parallel radiations of Nicaraguan crater lake cichlid fishes
Divergent selection is the main driving force in sympatric ecological speciation and may also play a strong role in divergence between allopatric populations. Characterizing the genome-wide impact of divergent selection constitutes often a first step in the process of unraveling the genetic bases underlying adaptation and ecological speciation. The Midas cichlid fish (Amphilophus citrinellus) species complex in Nicaragua is a powerful system for studying evolutionary processes. Independent colonizations of isolated young crater lakes by Midas cichlid populations from the older and great lakes of Nicaragua resulted in the repeated evolution of adaptive radiations by intralacustrine sympatric speciation. In this study we performed genome scans on two repeated radiations of crater lake species and their great lake source populations (1030 polymorphic AFLPs, n ≈ 30 individuals per species). We detected regions under divergent selection (0.3 % in the crater lake Xiloá flock and 1.7 % in the older crater lake Apoyo radiation) that might be responsible for the sympatric diversification. We find no evidence that the same genomic regions have been involved across crater lake flocks. The data provide evidence, however, for some genetic parallelism (seven out of 51 crater lake to great lake outlier loci are shared; 13.7%) associated with the allopatric divergence of both crater lake flocks. Furthermore, our results suggest that the number of outlier loci involved in sympatric and allopatric divergence increases with time. A phylogeny based on our data clearly supports the monophyly of both crater lake species flocks and provides evidence for a parallel branching order with a primary divergence along the limnetic-benthic axis in both radiations.
Data from: Correlated evolution of body and fin morphology in the cichlid fishes
Body and fin shape are chief determinants of swimming performance in fishes. Different configurations of body and fin shape can suit different locomotor specializations. The success of any configuration is dependent upon the hydrodynamic interactions between body and fins. Despite the importance of body-fin interactions for swimming, there are few data indicating whether body and fin configurations evolve in concert, or whether these structures vary independently. The cichlid fishes are a diverse family whose well-studied phylogenetic relationships make them ideal for the study of macroevolution of ecomorphology. This study measured body, caudal and median fin morphology from radiographs of 131 cichlid genera, using morphometrics and phylogenetic comparative methods to determine whether these traits exhibit correlated evolution. Partial least squares canonical analysis revealed that body, caudal fin, dorsal fin, and anal fin shapes all exhibited strong correlated evolution consistent with locomotor ecomorphology. Major patterns included the evolution of deep body profiles with long fins, suggestive of maneuvering specialization; and the evolution of narrow, elongate caudal peduncles with concave tails, a combination that characterizes economical cruisers. These results demonstrate that body shape evolution does not occur independently of other traits, but among a suite of other morphological changes that augment locomotor specialization.
Data from: Molecular phylogeny and revised classification of the haplotilapiine cichlid fishes formerly referred to as "Tilapia"
African cichlids formerly referred to as "Tilapia" represent a paraphyletic species assemblage belonging to the so called haplotilapiine lineage which gave rise to the spectacular East African cichlid radiations (EARs) as well as to globally important aquaculture species. We present a comprehensive molecular phylogeny of representative haplotilapiine cichlids, combining in one data set four mitochondrial and five nuclear loci for 76 species, and compare it with phylogenetic information of a second data set of 378 mitochondrial ND2 haplotypes representing almost all important "Tilapia" or Tilapia-related lineages as well as most EAR lineages. The monophyly of haplotilapiines is supported, as is the nested sister group relationship of Etia and mouthbrooding tilapiines with the remaining haplotilapiines. The latter are consistently placed in eight monophyletic clades over all datasets and analyses, but several dichotomous phylogenetic relationships appear compromised by cytonuclear discordant phylogenetic signal. Based on these results as well as on extensive morphological evidence we propose a novel generic and suprageneric classification including a (re-)diagnosis of 20 haplotilapiine cichlid genera and nine tribes. New tribes are provided for the former subgenera Coptodon Gervais, 1853, HeterotilapiaRegan, 1920 and PelmatolapiaThys van den Audenaerde, 1969, in addition for "Tilapia" joka, Tilapia sensu stricto and Chilochromis, Etia, Steatocranus sensu stricto, the mouthbrooding tilapiines and for a clade of West African tilapiines.
Data from: Social rank, color morph, and social network metrics predict oxidative stress in a cichlid fish
Dominance hierarchies are a fundamental part of social systems in many species and social rank can influence access to resources and impact health and physiology. While social subordination is a profound stressor, few studies consider the social stress experienced by dominant males due to constantly needing to defend their dominance status through costly aggressive displays. Recent studies suggest that in species that use body coloration to signal status, these costs may also be color morph-specific. Our study examines the link between the social rank, intensity of territorial defense, body coloration, and oxidative stress in males of the color polymorphic cichlid fish Astatotilapia burtoni where males are either blue or yellow. We studied behavior in naturalistic communities and examined circulating reactive oxygen metabolites and antioxidant defenses. We found that dominant males experience higher concentrations of circulating reactive oxygen metabolites without notably increasing their antioxidant defenses, but this effect was not related to color morph. Aggression and social network ties predicted oxidative stress in a morph-specific manner, with yellow but not blue males showing signs of increased oxidative damage with increasing agonistic effort. In contrast to expectation, oxidative stress was not influenced by cortisol or testosterone levels. We conclude that oxidative stress is instrumental to understanding the costs and benefits of high social rank.
Data from: Evolutionary divergence in life history traits among populations of the Lake Malawi cichlid fish Astatotilapia calliptera
During the early stages of adaptive radiation, populations diverge in life history traits such as egg size and growth rates, in addition to eco-morphological and behavioral characteristics. However, there are few studies of life history divergence within ongoing adaptive radiations. Here, we studied Astatotilapia calliptera, a maternal mouthbrooding cichlid fish within the Lake Malawi haplochromine radiation. This species occupies a rich diversity of habitats, including the main body of Lake Malawi, as well as peripheral rivers and shallow lakes. We used common garden experiments to test for life history divergence among populations, focussing on clutch size, duration of incubation, egg mass, offspring size, and growth rates. In a first experiment, we found significant differences among populations in average clutch size and egg mass, and larger clutches were associated with smaller eggs. In a second experiment, we found significant differences among populations in brood size, duration of incubation, juvenile length when released, and growth rates. Larger broods were associated with smaller juveniles when released and shorter incubation times. Although juvenile growth rates differed between populations, these were not strongly related to initial size on release. Overall, differences in life history characters among populations were not predicted by major habitat classifications (Lake Malawi or peripheral habitats) or population genetic divergence (microsatellite-based FST). We suggest that the observed patterns are consistent with local selective forces driving the observed patterns of trait divergence. The results provide strong evidence of evolutionary divergence and covariance of life history traits among populations within a radiating cichlid species, highlighting opportunities for further work to identify the processes driving the observed divergence.
Data from: The melanocortin system regulates body pigmentation and social behaviour in a colour polymorphic cichlid fish
The melanocortin system is a neuroendocrine system that regulates a range of physiological and behavioural processes. We examined the extent to which the melanocortin system simultaneously regulates colour and behaviour in the cichlid fish Astatotilapia burtoni. We found that yellow males are more aggressive than blue males, in line with previous studies. We then found that exogenous α-melanocyte-stimulating hormone (α-MSH) increases yellowness of the body and dispersal of xanthophore pigments in both morphs. However, α-MSH had a morph-specific effect on aggression, with only blue males showing an increase in the rate of aggression. Exogenous agouti signalling peptide (ASIP), a melanocortin antagonist, did not affect coloration but reduced the rate of aggression in both colour morphs. Blue males had higher cortisol levels than yellow males. Neural gene expression of melanocortin receptors (mcr) and ligands was not differentially regulated between colour morphs. In the skin, however, mc1r and pro-opiomelanocortin (pomc) β were upregulated in blue males, while asip 1 was upregulated in yellow males. The effects of α-MSH on behaviour and body coloration, combined with morph-specific regulation of the stress response and the melanocortin system, suggest that the melanocortin system contributes to the polymorphism in behaviour and coloration in A. burtoni.
Data from: Reverting ontogeny: rapid phenotypic plasticity of color vision in cichlid fish
Phenotypic plasticity, particularly during development, allows organisms to rapidly adjust to different environmental conditions. Yet, it is often unclear whether the extent and direction of plastic changes are restricted by an individual's ontogeny. Many species of cichlid fishes go through ontogenetic changes in visual sensitivity, from short to long wavelengths, by switching expression of cone opsin genes crucial for color vision. During this progression, individuals often exhibit phenotypic plasticity to the ambient light conditions. However, it is commonly assumed that once an adult visual phenotype is reached, reverting to an earlier ontogenetic state with higher sensitivity at shorter wavelengths is not common. In this study, we experimentally demonstrate that four-month-old Midas cichlid fish (Amphilophus astorquii) show plasticity in single cone opsin expression after experiencing drastic changes in light conditions. Resulting shifts of visual sensitivity occurred presumably in an adaptive direction - towards shorter or longer wavelengths when exposed to short or long wavelength light, respectively. Single cone opsin expression changed within only a few days and went through a transitional phase of co-expression. When the environment was experimentally enriched in long wavelength light, the corresponding change occurred gradually along a dorsoventral gradient within the retina. This plasticity allowed individuals to revert earlier ontogenetic changes and return to a more juvenile visual phenotype demonstrating previously unrecognized insights into temporal and spatial dynamics of phenotypic plasticity of the visual system in response to ambient light.
Data from: High levels of interspecific gene flow in an endemic cichlid fish adaptive radiation from an extreme lake environment
Studying recent adaptive radiations in isolated insular systems avoids complicating causal events and thus may offer clearer insight into mechanisms generating biological diversity. Here, we investigate evolutionary relationships and genomic differentiation within the recent radiation of Alcolapia cichlid fish that exhibit extensive phenotypic diversification, and which are confined to the extreme soda lakes Magadi and Natron in East Africa. We generated an extensive RAD data set of 96 individuals from multiple sampling sites and found evidence for genetic admixture between species within Lake Natron, with the highest levels of admixture between sympatric populations of the most recently diverged species. Despite considerable environmental separation, populations within Lake Natron do not exhibit isolation by distance, indicating panmixia within the lake, although individuals within lineages clustered by population in phylogenomic analysis. Our results indicate exceptionally low genetic differentiation across the radiation despite considerable phenotypic trophic variation, supporting previous findings from smaller data sets; however, with the increased power of densely sampled SNPs, we identify genomic peaks of differentiation (FST outliers) between Alcolapia species. While evidence of ongoing gene flow and interspecies hybridization in certain populations suggests that Alcolapia species are incompletely reproductively isolated, the identification of outlier SNPs under diversifying selection indicates the radiation is undergoing adaptive divergence.
Data from: A population genetic assessment of taxonomic species: the case of Lake Malawi cichlid fishes
Organisms sampled for population level research are typically assigned to species by morphological criteria. But if those criteria are limited to one sex or life stage, or the organisms come from a complex of closely related forms, the species assignments may misdirect analyses. The impact of such sampling can be assessed from the correspondence of genetic clusters, identified only from patterns of genetic variation, to the species identified using only phenotypic criteria. We undertook this protocol with the rock-dwelling mbuna cichlids of Lake Malawi, for which species within genera are usually identified by investigators using adult male coloration patterns. Given high local endemism of male color patterns, and considerable allele sharing among species, there persists considerable taxonomic uncertainty in these fishes. Over 700 individuals from a single transect were photographed, genotyped, and separately assigned: (1) to morphospecies using photographs; and (2) to genetic clusters using five widely used methods. Overall, the correspondence between clustering methods was strong for larger clusters, but methods varied widely in estimated number of clusters. The correspondence between morphospecies and genetic clusters was also strong for larger clusters, as well as some smaller clusters for some methods. These analyses generally affirm (1) adult male-limited sampling and (2) the taxonomic status of Lake Malawi mbuna, as the species in our study largely appear to be well-demarcated genetic entities. More generally, our analyses highlight the challenges for clustering methods when the number of populations is unknown, especially in cases of highly uneven sample sizes.
Data from: Genomic architecture of ecologically divergent body shape in a pair of sympatric crater lake cichlid fishes
Determining the genetic bases of adaptations and their roles in speciation are prominent issues in evolutionary biology. Cichlid fish species flocks are a prime example of recent rapid radiations often associated with adaptive phenotypic divergence from a common ancestor within a short period of time. In several radiations of freshwater fishes divergence in eco-morphological traits including body shape, color, lips and jaws, are thought to underlie their ecological differentiation, specialization and – ultimately – speciation. The Midas cichlid species complex (Amphilophus spp.) of Nicaragua provides one of the few known examples of sympatric speciation where species have rapidly evolved different but parallel morphologies in young crater lakes. This study identified significant QTL for body shape, using SNPs generated via ddRAD sequencing and geometric morphometric analyses of a cross between two ecologically and morphologically divergent, sympatric cichlid species endemic to crater Lake Apoyo: an elongated limnetic species (A. zaliosus) and a high-bodied benthic species (A. astorquii). A total of 453 genome-wide informative SNPs were identified in 240 F2 hybrids. These markers were used to construct a genetic map in which 25 linkage groups were resolved. Seventy-two segregating SNPs were linked to 11 QTL. By annotating the two most highly supported QTL-linked genomic regions, genes that might contribute to divergence in body shape along the benthic-limnetic axis in Midas cichlid sympatric adaptive radiations were identified. These results suggest that few genomic regions of large effect contribute to early-stage divergence in Midas cichlids.
Data from: Agouti-related peptide 2 facilitates convergent evolution of stripe patterns across cichlid fish radiations
The color patterns of African cichlid fishes provide notable examples of phenotypic convergence. Across the more than 1200 East African rift lake species, melanic horizontal stripes have evolved numerous times. We discovered that regulatory changes of the gene agouti-related peptide 2 (agrp2) act as molecular switches controlling this evolutionarily labile phenotype. Reduced agrp2 expression is convergently associated with the presence of stripe patterns across species flocks. However, cis-regulatory mutations are not predictive of stripes across radiations, suggesting independent regulatory mechanisms. Genetic mapping confirms the link between the agrp2 locus and stripe patterns. The crucial role of agrp2 is further supported by a CRISPR-Cas9 knockout that reconstitutes stripes in a nonstriped cichlid. Thus, we unveil how a single gene affects the convergent evolution of a complex color pattern.
FIGURE 4 in Crenicichla hu, a new species of cichlid fish (Teleostei: Cichlidae) from the Paraná basin in Misiones, Argentina
FIGURE 4. Crenicichla hu female, live specimen, paratype, MACN-ict 9430, 122.0 mm.
FIGURE 3 in Crenicichla hu, a new species of cichlid fish (Teleostei: Cichlidae) from the Paraná basin in Misiones, Argentina
FIGURE 3. Crenicichla hu male, live specimen, paratype, MACN-ict 9430, 153.0 mm.
FIGURE 9 in Krobia xinguensis, a new species of cichlid fish from the Xingu River drainage in Brazil (Teleostei: Cichlidae)
FIGURE 9. Collecting sites of Krobia xinguensis.
FIGURE 4. Krobia petitella n in Krobia petitella, a new species of cichlid fish from the Berbice River in Guyana (Teleostei: Cichlidae)
FIGURE 4. Krobia petitella n. sp.. Lower pharyngeal jaw toothplate, from ROM 86851, 57.3 mm SL.
FIGURE 7 in Crenicichla gillmorlisi, a new species of cichlid fish (Teleostei: Cichlidae) from the Paraná river drainage in Paraguay
FIGURE 7. Habitat of Crenicichla gillmorlisi at Paso Itá, Hernandarías, Paraguay.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
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The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
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