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opencc-zeroAug 2022View details →

Quantitative trait loci mapping in cichlid fishes: Aulonocara koningsi x Metriaclima mbenjii and Labidochromis caeruleus x Labeotropheus trewavasae

Since the time of Darwin, biologists have sought to understand the evolution and origins of phenotypic variation. To understand the genetic and molecular sources of morphological differences, we capitalize on the cichlid fish system. Cichlids of the East African Rift Lakes have undergone an extensive adaptive radiation, including variation in body shape, head shape, and pigmentation. These morphological differences are often intimately linked to the ecology and behavior of these animals. Here, we investigate the genetic basis of these phenotypes using quantitative trait loci (QTL) mapping using four genera of Lake Malawi cichlids and two F2 hybrid populations. The first hybrid cross is between Aulonocara koningsi, which lives in the open sandy region and feeds insects from the open sand, and Metriaclima mbenjii, an omnivore rock-dwelling fish. The second cross is between Labidochromis caeruleus, a suction-feeding insectivore that swims continuously searching for prey, and Labeotropheus trewavasae, which feeds by biting or scraping attached algae from the rocks in its benthic habitat. Such work can provide insights into the molecular basis of phenotypic adaptation, the genetic architecture of morphology, and the evolution of cichlid fishes.

opencc-by-4.0Apr 2012View details →

Supplementary material 1 from: Venere P, Valente G, Vitorino C, Cabral-de-Mello D, Oliveira C, Souza I, Martins C (2012) Comparative cytogenetics of ten species of cichlid fishes (Teleostei, Cichlidae) from the Araguaia River system, Brazil, by conventional cytogenetic methods. Comparative Cytogenetics 6(2): 163-181. https://doi.org/10.3897/compcytogen.v6i2.1739

Table with synthesis of karyotypic traits of cichlids.

opencc-by-4.0Sep 2013View details →

Fig. 9 in Reproductive cycle of the Neotropical cichlid yellow peacock bass Cichla kelberi: A novel pattern of testicular development

Fig. 9. Gonadosomatic Index (GSI) of the testicular maturation phases in C. kelberi.

opencc-by-4.0Sep 2013View details →

Fig. 2 in Reproductive cycle of the Neotropical cichlid yellow peacock bass Cichla kelberi: A novel pattern of testicular development

Fig. 2. Gonadal development Phases of C. kelberi along the reproductive cycle. H.E. stain.

opencc-zeroJul 2024View details →

Data for: Multiple behavioral mechanisms shape development in a highly social cichlid fish

Early-life social experiences shape adult phenotype, yet the underlying behavioral mechanisms remain poorly understood. We manipulated early-life social experience in the highly social African cichlid fish Astatotilapia burtoni to investigate the effects on behavior and stress axis function in juveniles. Juveniles experienced different numbers of social partners in stable pairs (1 partner), stable groups (6 fish; 5 partners), and socialized pairs (a novel fish was exchanged every 5 days; 5 partners). Treatments also differed in group size (groups vs. pairs) and stability (stable vs. socialized). We then measured individual behavior and water-borne cortisol to identify effects of early-life experience. We found treatment differences in behavior across all assays: open field exploration, social cue investigation, dominant behavior, and subordinate behavior. Treatment did not affect cortisol. Principal components (PC) analysis revealed robust co-variation of behavior across contexts, including with cortisol, to form behavioral syndromes sensitive to early-life social experience. PC1 (25.1 %) differed by social partner number: juveniles with more partners (groups and socialized pairs) were more exploratory during the social cue investigation, spent less time in the territory, and were more interactive as dominants. PC5 (8.5 %) differed by stability: socialized pairs were more dominant, spent less time in and around the territory, were more socially investigative, and had lower cortisol than stable groups or pairs. Observations of the home tanks provided insights into the social experiences that may underlie these effects. These results contribute to our understanding of how early-life social experiences are accrued and exert strong, lasting effects on phenotype.

opencc-zeroDec 2015View details →

Data from: Genetic and developmental basis for fin shape variation in African cichlid fishes

Adaptive radiations are often characterized by the rapid evolution of traits associated with divergent feeding modes. For example, the evolutionary history of African cichlids is marked by repeated and coordinated shifts in skull, trophic, fin and body shape. Here, we seek to explore the molecular basis for fin shape variation in Lake Malawi cichlids. We first described variation within an F2 mapping population derived by crossing two cichlid species with divergent morphologies including fin shape. We then used this population to genetically map loci that influence variation in this trait. We found that the genotype–phenotype map for fin shape is largely distinct from other morphological characters including body and craniofacial shape. These data suggest that key aspects of fin, body and jaw shape are genetically modular and that the coordinated evolution of these traits in cichlids is more likely due to common selective pressures than to pleiotropy or linkage. We next combined genetic mapping data with population-level genome scans to identify wnt7aa and col1a1 as candidate genes underlying variation in the number of pectoral fin ray elements. Gene expression patterns across species with different fin morphologies and small molecule manipulation of the Wnt pathway during fin development further support the hypothesis that variation at these loci underlies divergence in fin shape between cichlid species. In all, our data provide additional insights into the genetic and molecular mechanisms associated with morphological divergence in this important adaptive radiation.

Fig. 7 in Social and reproductive physiology and behavior of the Neotropical cichlid fish Cichlasoma dimerus under laboratory conditions

Fig. 7. Semiquantitative analysis of pituitary hormone content

Fig. 5. Reproductive territorial male attacking a in Social and reproductive physiology and behavior of the Neotropical cichlid fish Cichlasoma dimerus under laboratory conditions

Fig. 5. Reproductive territorial male attacking a non reproductive territorial male.

Fig. 6 in Social and reproductive physiology and behavior of the Neotropical cichlid fish Cichlasoma dimerus under laboratory conditions

Fig. 6. Plasma cortisol levels in reproductive territorial (RT)

Fig. 3 in Social and reproductive physiology and behavior of the Neotropical cichlid fish Cichlasoma dimerus under laboratory conditions

Fig. 3. Image showing aggressive physical contact between two males, referred to as mouth holding.

opencc-by-4.0Sep 2011View details →

Fig. 1 in Population structure and reproductive behavior of Sinaloa cichlid Cichlasoma beani (Jordan, 1889) in a tropical reservoir

Fig. 1. Aguamilpa Reservoir, Nayarit, Mexico. Black dots indicate landing sites and sampling areas.

opencc-by-4.0Dec 2008View details →

Fig. 3 in Ecology and life history of an Amazon floodplain cichlid: the discus fish Symphysodon (Perciformes: Cichlidae)

Fig. 3. Sampling of a small submerged tree crown or 'galhada'

opencc-zeroNov 2022View details →

Data from: Dual function and associated costs of a highly exaggerated trait in a cichlid fish

Exaggerated secondary sexual characteristics are apparently costly and seem to defy natural selection. This conundrum prompted Charles Darwin to propose the theory of sexual selection. Accordingly, exaggerated secondary sexual characteristics might be ornaments on which female choice is based and/or armaments used during male-male competition. Males of many cichlid fish species, including the adaptive radiation of Nicaraguan Midas cichlids, develop a highly exaggerated nuchal hump, which is thought to be a sexually selected trait. To test this hypothesis, we conducted a series of behavioral assays in F2 hybrids obtained from crossing a species with a relatively small hump and one with an exaggerated hump. Mate-choice experiments showed a clear female preference for males with large humps. In an open-choice experiment with limited territories, couples including large humped males were more successful in acquiring these territories. Therefore, nuchal humps appear to serve dual functions as an ornament for attracting mates and as an armament for direct contest with rivals. Although being beneficial in terms of sexual selection, this trait also imposes fitness costs on males possessing disproportionally large nuchal humps since they exhibit decreased endurance and increased energetic costs when swimming. We conclude that these costs illustrate trade-offs associated with large hump size between sexual and natural selection, which causes the latter to limit further exaggeration of this spectacular male trait.

opencc-zeroDec 2021View details →

Morphological data from: Strong species structure but weak geographical structure in demersal Lake Victoria cichlids

Studying phenotypic and genetic differentiation between very young species can be very informative with regard to learning about processes of speciation. Identifying and characterizing genetic species structure and distinguishing it from spatial genetic structure within a species is a prerequisite for this and is often not given sufficient attention. Young radiations of cichlid fish are classical speciation study systems. However, it is only during the past decade that population genomics based on next-generation sequencing has begun to provide the power to resolve species and distinguish speciation from spatial population structure for the youngest of these radiations. The Lake Victoria haplochromine cichlids constitute the youngest large cichlid fish radiation, probably less than 20,000 years old. Earlier work showed that communities of rocky reef cichlids are composed of many reciprocally monophyletic species despite their very recent origins. Here, we build on this work by studying assemblages of offshore demersal cichlids, adding analyses of within-species spatial structure to the sympatric species structure. We sampled seven multispecies communities along a 6km-long transect from one side of the Mwanza Gulf to the other side. We investigated whether phenotypically diagnosed putative species are reciprocally monophyletic and whether such monophyly is stable across species geographic ranges. We show that all species are genetically strongly differentiated in sympatry, that they are reciprocally monophyletic and that monophyly is stable across distribution ranges. We found significant differentiation between geographically distinct populations in two species, but no or weak isolation-by-distance. We further found subtle but significant morphological differences between all species and a linear relationship between genomic and morphological distance which suggests that differences in morphology begin to accumulate after speciation has already affected genome-wide restrictions of gene flow.

opencc-zeroOct 2023View details →

Effect of the histone deacetylase inhibitor Trichostatin A on facial development in cichlid fishes

A central question in biology is the molecular origins of phenotypic diversity. While genetic changes are key to the genotype-phenotype relationship, alterations to chromatin structure and the physical packaging of histone proteins may also be important drivers of vertebrate divergence. We investigate the impact of such an epigenetic mechanism, histone acetylation, within a textbook example of an adaptive radiation. Cichlids of Lake Malawi have adapted diverse craniofacial structures, and here we investigate how histone acetylation influences morphological variation in these fishes. Specifically, we assessed the effect of inhibiting histone deacetylation using the drug trichostatin A (TSA) on developing facial structures. We examined this during three critical developmental windows in two cichlid species with alternate adult morphologies. Exposure to TSA during neural crest cell (NCC) migration and as post-migratory NCCs proliferate into the pharyngeal arches resulted in significant changes in lateral and ventral shape in Maylandia, but not in Tropheops. This included an overall shortening of the head, widening of the lower jaw, and steeper craniofacial profile, all of which are paedomorphic morphologies. In contrast, treatment with TSA during early chondrogenesis did not result in significant morphological changes in either species. Together, these data suggest a sensitivity to epigenetic alterations that are both time- and species-dependent. We find that morphologies are due to non-autonomous or potentially indirect effects on NCC development, including in part a global developmental delay. Our research bolsters the understanding that proper histone acetylation is essential for early craniofacial development and identifies a species-specific robustness to developmental change. Overall, this study demonstrates how epigenetic regulation may play an important role in both generating and buffering morphological variation.