Biology subjects

Maan, M. E.

Publications and source records attributed to Maan, M. E..

4 recordsLinked to original sources

bioRxiv2022

Diurnality shapes the visual opsin genes of colorful Neotropical frogs

Amphibians are ideal for studying visual system evolution because their biphasic (aquatic and terrestrial) life history and ecological diversity expose them to a broad range of visual conditions. Here we evaluate signatures of selection on visual opsin genes across Neotropical anurans and focus on three diurnal clades that are well-known for the concurrence of conspicuous colors and chemical defense (i.e., aposematism): poison frogs (Dendrobatidae), Harlequin toads (Bufonidae: Atelopus), and pumpkin toadlets (Brachycephalidae: Brachycephalus). We found evidence of positive selection on 44 amino acid sites in LWS, SWS1, SWS2, and RH1 opsin genes, of which one in LWS and two in RH1 have been previously identified as spectral tuning sites in other vertebrates. Given that anurans have mostly nocturnal habits, the patterns of selection revealed new sites that might be important in spectral tuning for frogs, potentially for adaptation to diurnal habits and for color-based intraspecific communication. Furthermore, we provide evidence that SWS2, normally expressed in rod cells in amphibians, has likely been lost in the ancestor of Dendrobatidae, suggesting that under low-light levels, dendrobatids have inferior wavelength discrimination compared to other frogs. This loss might follow the origin of diurnal activity in dendrobatids and could have implications for their chemical ecology, biodiversity, and behavior. Our analyses show that assessments of opsin diversification in understudied groups could expand our understanding of the role of sensory system evolution in ecological adaptation.

evolutionary biology↗

bioRxiv2021

Contribution of opsins and chromophores to cone pigment variation across populations of Lake Victoria cichlids

Adaptation to heterogeneous sensory environments has been implicated as a key parameter in speciation. Cichlid fish are a textbook example of divergent visual adaptation, mediated by variation in the sequences and expression levels of cone opsin genes (encoding the protein component of visual pigments). In some vertebrates including fish, visual sensitivity is also tuned by the ratio of Vitamin A1/A2-derived chromophores (i.e. the light-sensitive component of the visual pigment, bound to the opsin protein), where higher proportions of A2 cause a more red-shifted wavelength absorbance. Here, we explore variation in chromophore ratios across multiple cichlid populations in Lake Victoria, using as a proxy the enzyme CYP27C1 that catalyses the conversion of Vitamin A1-into A2. We focus on sympatric Pundamilia cichlids, where species with blue or red male coloration co-occur at multiple islands, but occupy different depths and consequently different visual habitats. In the red species, we found higher cyp27c1 expression in populations from turbid-water than from clear-water locations, but there was no such pattern in the blue species. Across populations, differences between the sympatric species in cyp27c1 expression had a consistent relationship with species differences in opsin expression patterns, but the red/blue identity reversed between clear- and turbid-water locations. To assess the contribution of heritable versus environmental causes of variation, we tested whether light manipulations induce a change in cyp27c1 expression in the laboratory. We found that cyp27c1 expression was not influenced by experimental light conditions, suggesting that the observed variation in the wild is due to genetic differences. Establishing the biological importance of this variation requires testing the link between cyp27c1 expression and A1/A2 ratios in the eye, as well as its consequences for visual performance.

evolutionary biology↗

bioRxiv2021

Four new species of Cichlidogyrus (Platyhelminthes, Monogenea, Dactylogyridae) from Lake Victoria haplochromine cichlid fishes, with the redescription of C. bifurcatus and C. longipenis

African cichlids are model systems for evolutionary studies and for host-parasite interactions, because of their adaptive radiations and because they harbour many species of monogenean parasites with high host-specificity. Here, we sampled five locations in southern Lake Victoria, the youngest of the African Great Lakes. We surveyed gillinfecting monogeneans from 18 cichlid species belonging to the Lake Victoria radiation superflock and two cichlid species representing two older and distantly related lineages. We found one species of Gyrodactylus (Gyrodactylidae, Monogenea), Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011, and seven species of Cichlidogyrus (Dactylogyridae, Monogenea). Four species are herein described: Cichlidogyrus pseudodossoui n. sp., C. nyanza n. sp., C. furu n. sp., C. vetusmolendarius n. sp.. Another species is reported but not formally described (because of few specimens and morphological similarity with C. furu n. sp.). Two other species are redescribed: Cichlidogyrus bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Our results confirm that the monogenean fauna of Victorian littoral cichlids displays lower species richness and lower host-specificity than that of Lake Tanganyika littoral cichlids. In C. furu n. sp., hooks V are clearly longer than the other hooks, highlighting the need to re-evaluate the current classification system of haptoral configurations that considers hook pairs III-VII as rather uniform. Some morphological features of C. bifurcatus, C. longipenis and C. nyanza n. sp. suggest that these are closely related to other congeners that infect haplochromines. We also found morphological indications that representatives of Cichlidogyrus colonised Lake Victoria haplochromines or their ancestors at least twice, which is in line with the Lake Victoria superflock being colonized by two cichlid tribes (Haplochromini and Oreochromini). DisclaimerThis preprint is disclaimed for purposes of Zoological Nomenclature in accordance with the International Code of Zoological Nomenclature, Fourth Edition Articles 8.2 and 8.3 (ICZN 1999). No new names or nomenclatural changes are available from statements in this preprint. Resume - Quatre especes nouvelles de Cichlidogyrus (Platyhelminthes, Monogenea, Dactylogyridae) parasites dhaplochromine (Cichlidae) du lac Victoria, avec la redescription de C. bifurcatus and C. longipenisA cause des radiations adaptatives quils ont subies, les cichlides africain sont des systemes modeles pour etudier levolution, mais aussi les relations hotes/parasites, car ils hebergent de nombreuses especes de Monogenes parasites qui presentent une specificite etroite vis-a-vis de leurs hotes. Dans ce travail, nous avons echantillonne cinq localites dans le Sud du lac Victoria, le plus jeune des grands lacs dAfrique de lEst. Nous avons examine les Monogenes presents sur les branchies de 18 especes de Cichlides appartenant a la radiation adaptative << superflock >> du lac Victoria et de deux especes representant deux lignees anciennes et non etroitement apparentees. Nous avons trouve une espece de Gyrodactylus (Gyrodactylidae, Monogenea), Gyrodactylus sturmbaueri Vanhove, Snoeks, Volckaert & Huyse, 2011 et sept especes de Cichlidogyrus (Dactylogyridae, Monogenea). Quatre especes nouvelles sont decrites dans le present travail : Cichlidogyrus pseudodossoui n. sp., C. nyanza n. sp., C. furu n. sp., C. vetusmolendarius n. sp.. Une est signalee mais non decrite formellement (trop peux dindividus recueillis, morphologiquement proche de C. furu n. sp.). Deux autres sont redecrites : Cichlidogyrus bifurcatus Paperna, 1960 and C. longipenis Paperna & Thurston, 1969. Nos resultats confirment que la faune des Monogenes des Cichlides du lac Victoria fait preuve dune richesse specifique et dune specificite moins importante que celle du lac Tanganyika. Chez C. furu n. sp. la paire de crochet V etant nettement plus longue que les autres, il faudra reconsiderer le systeme de classification actuel des types de hapteurs chez les Cichlidogyrus, qui considere que tous les crochets (III a VII) ont la meme taille. Quelques caracteristiques morphologiques de C. bifurcatus, C. longipenis et C. nyanza n. sp. pourraient etre la preuve dune ascendance commune avec des congeneres presents chez dautres Haplochromines. De meme, certains caracteres indiqueraient que des representants des Cichlidogyrus ont colonise les Haplochromines du lac Victoria, ou leurs ancetres, au moins a deux reprises, ce qui est coherent avec une colonisation du lac par deux lignees de cichlides distinctes (Haplochromini and Oreochromini).

zoology↗

bioRxiv2018

Visual adaptation and microhabitat choice in Lake Victoria cichlid fish

When different genotypes choose different habitats to better match their phenotypes, adaptive differentiation within a population may be promoted. Mating within those habitats may subsequently contribute to reproductive isolation. In cichlid fish, visual adaptation to alternative visual environments is hypothesised to contribute to speciation. Here, we investigated whether variation in visual sensitivity causes different visual habitat preferences, using two closely related cichlid species that occur at different but overlapping water depths in Lake Victoria and that differ in visual perception (Pundamilia sp.). In addition to species differences, we explored potential effects of visual plasticity, by rearing fish in two different light conditions: broad-spectrum (mimicking shallow water) or red-shifted (mimicking deeper waters). Contrary to expectations, fish did not prefer the light environment that mimicked their typical natural habitat. Instead, we found an overall preference for the broad-spectrum environment. We also found a transient influence of the rearing condition, indicating that assessment of microhabitat preference requires repeated testing to control for familiarity effects. Together, our results show that cichlid fish exert visual habitat preference, but do not support straightforward visual habitat matching.

evolutionary biology↗