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Nothobranchius annual killifishes.

ABSTRACT: Annual fishes of the genus Nothobranchius inhabit ephemeral habitats in Eastern and Southeastern Africa. Their life cycle is characterized by very rapid maturation, a posthatch lifespan of a few weeks to months and embryonic diapause to survive the dry season. The species N. furzeri holds the record of the fastest-maturing vertebrate and of the vertebrate with the shortest captive lifespan and is emerging as model organism in biomedical research, evolutionary biology, and developmental biology. Extensive characterization of age-related phenotypes in the laboratory and of ecology, distribution, and demography in the wild are available. Species/populations from habitats differing in precipitation intensity show parallel evolution of lifespan and age-related traits that conform to the classical theories on aging. Genome sequencing and the establishment of CRISPR/Cas9 techniques made this species particularly attractive to investigate the effects genetic and non-genetic intervention on lifespan and aging-related phenotypes. At the same time, annual fishes are a very interesting subject for comparative approaches, including genomics, transcriptomics, and proteomics. The N. furzeri community is highly diverse and rapidly expanding and organizes a biannual meeting.

SUBMITTER: Terzibasi Tozzini E

PROVIDER: S-EPMC7739477 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Nothobranchius annual killifishes.

Terzibasi Tozzini Eva E Cellerino Alessandro A

EvoDevo 20201215 1

Annual fishes of the genus Nothobranchius inhabit ephemeral habitats in Eastern and Southeastern Africa. Their life cycle is characterized by very rapid maturation, a posthatch lifespan of a few weeks to months and embryonic diapause to survive the dry season. The species N. furzeri holds the record of the fastest-maturing vertebrate and of the vertebrate with the shortest captive lifespan and is emerging as model organism in biomedical research, evolutionary biology, and developmental biology. ...[more]

PMID: 33323125

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Project description:BackgroundThe annual fish Nothobranchius furzeri is characterized by a natural dichromatism with yellow-tailed and red-tailed male individuals. These differences are due to different distributions of xanthophores and erythrophores in the two morphs. Previous crossing studies have showed that dichromatism in N. furzeri is inherited as a simple Mendelian trait with the yellow morph dominant over the red morph. The causative genetic variation was mapped by linkage analysis in a chromosome region containing the Mc1r locus. However, subsequent mapping showed that Mc1r is most likely not responsible for the color difference in N. furzeri. To gain further insight into the molecular basis of this phenotype, we performed RNA-seq on F2 progeny of a cross between N. furzeri male and N. kadleci female.ResultsWe identified 210 differentially-expressed genes between yellow and red fin samples. Functional annotation analysis revealed that genes with higher transcript levels in the yellow morph are enriched for the melanin synthesis pathway indicating that xanthophores are more similar to melanophores than are the erythrophores. Genes with higher expression levels in red-tails included xanthine dehydrogenase (Xdh), coding for a biosynthetic enzyme in the pteridine synthesis pathway, and genes related to muscle contraction. Comparison of DEGs obtained in this study with genes associated with pigmentation in the Midas cichlid (A. citrinellus) reveal similarities like involvement of the melanin biosynthesis pathway, the genes Ptgir, Rasef (RAS and EF-hand domain containing), as well as genes primarily expressed in muscle such as Ttn and Ttnb (titin, titin b).ConclusionsRegulation of genes in the melanin synthetic pathway is an expected finding and shows that N. furzeri is a genetically-tractable species for studying the genetic basis of natural phenotypic variations. The current list of differentially-expressed genes can be compared with the results of fine-mapping, to reveal the genetic architecture of this natural phenotype. However, an evolutionarily-conserved role of muscle-related genes in tail fin pigmentation is novel finding and interesting perspective for the future.

Project description:BackgroundAdaptive radiations are triggered by ecological opportunity - the access to novel niche domains with abundant available resources that facilitate the formation of new ecologically divergent species. Therefore, as new species saturate niche space, clades experience a diversity-dependent slowdown of diversification over time. At the other extreme of the radiation continuum, non-adaptively radiating lineages undergo diversification with minimal niche differentiation when 'spatial opportunity' (i.e. areas with suitable 'ancestral' ecological conditions) is available. Traditionally, most research has focused on adaptive radiations, while empirical studies on non-adaptive radiations remain lagging behind. A prolific clade of African fish with extremely short lifespan (Nothobranchius killifish), show the key evolutionary features of a candidate non-adaptive radiation - primarily allopatric species with minimal niche and phenotypic divergence. Here, we test the hypothesis that Nothobranchius killifish have non-adaptively diversified. We employ phylogenetic modelling to investigate the tempo and mode of macroevolutionary diversification of these organisms.ResultsNothobranchius diversification has proceeded with minor niche differentiation and minimal morphological disparity among allopatric species. Additionally, we failed to identify evidence for a role of body size or biogeography in influencing diversification rates. Diversification has been homogeneous within this genus, with the only hotspot of species-richness not resulting from rapid diversification. However, species in sympatry show higher disparity, which may have been caused by character displacement among coexisting species.ConclusionsNothobranchius killifish have proliferated following the tempo and mode of a non-adaptive radiation. Our study confirms that this exceptionally short-lived group have diversified with minimal divergent niche adaptation, while one group of coexisting species seems to have facilitated spatial overlap among these taxa via the evolution of ecological character displacement.

Project description:BACKGROUND:Intraspecific genetic variation of African fauna has been significantly affected by pronounced climatic fluctuations in Plio-Pleistocene, but, with the exception of large mammals, very limited empirical data on diversity of natural populations are available for savanna-dwelling animals. Nothobranchius furzeri is an annual fish from south-eastern Africa, inhabiting discrete temporary savannah pools outside main river alluvia. Their dispersal is limited and population processes affecting its genetic structure are likely a combination of those affecting terrestrial and aquatic taxa. N. furzeri is a model taxon in ageing research and several populations of known geographical origin are used in laboratory studies. Here, we analysed the genetic structure, diversity, historical demography and temporal patterns of divergence in natural populations of N. furzeri across its entire distribution range. RESULTS:Genetic structure and historical demography of N. furzeri were analysed using a combination of mitochondrial (partial cytochrome b sequences, 687 bp) and nuclear (13 microsatellites) markers in 693 fish from 36 populations. Genetic markers consistently demonstrated strong population structuring and suggested two main genetic groups associated with river basins. The split was dated to the Pliocene (>2 Mya). The northern group inhabits savannah pools across the basin of the intermittent river Chefu in south-western Mozambique and eastern Zimbabwe. The southern group (from southernmost Mozambique) is subdivided, with the River Limpopo forming a barrier (maximum divergence time 1 Mya). A strong habitat fragmentation (isolated temporary pools) is reflected in significant genetic structuring even between adjacent pools, with a major influence of genetic drift and significant isolation-by-distance. Analysis of historical demography revealed that the expansion of both groups is ongoing, supported by frequent founder effects in marginal parts of the range and evidence of secondary contact between Chefu and Limpopo populations. CONCLUSIONS:We demonstrated: (1) ancient (pre-Pleistocene) divergence between the two main N. furzeri lineages, their recent secondary contact and lack of reproductive isolation; (2) important genetic structuring attributed to the fragmented nature of their environment and isolation-by-distance, suggesting that dispersal is limited, occurs over short distances and is not directly associated with river routes; (3) an apparent role of the River Limpopo as a barrier to dispersal and gene flow.

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Nothobranchius annual killifishes.

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Nothobranchius annual killifishes.

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