The evolutionary forces shaping life history divergence within species are largely unknown. Turquoise killifish display differences in lifespan among wild populations, representing an ideal natural experiment in evolution and diversification of life history. By combining genome sequencing and population genetics, we investigate the evolutionary forces shaping lifespan among wild turquoise killifish populations. We generate an improved reference genome assembly and identify genes under positive and purifying selection, as well as those evolving neutrally. Short-lived populations from the outer margin of the species range have small population size and accumulate deleterious mutations in genes significantly enriched in the WNT signaling pathway, neurodegeneration, cancer and the mTOR pathway. We propose that limited population size due to habitat fragmentation and repeated population bottlenecks, by increasing the genome-wide mutation load, exacerbates the effects of mutation accumulation and cumulatively contribute to the short adult lifespan.

• MeSH
• akumulace mutací * MeSH
• biologická evoluce MeSH
• dlouhověkost genetika   MeSH
• ekosystém MeSH
• Fundulidae MeSH
• genom genetika   MeSH
• hustota populace * MeSH
• modely u zvířat MeSH
• molekulární evoluce * MeSH
• stárnutí genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

In natural populations, individuals experience daily fluctuations in environmental conditions that synchronise endogenous biorhythms. Artificial alterations of environmental fluctuations can have negative consequences for life history traits, including lifespan. In laboratory studies of aging, the role of fluctuating temperature is usually overlooked and we know little of how thermal fluctuation modulates senescence in vertebrates. In this longitudinal study we followed individually-housed turquoise killifish, Nothobranchius furzeri, from two thermal regimes; ecologically relevant diel fluctuations (20 °C - 35 °C) and stable temperature (27.5 °C), and compared their survival, growth and reproduction. Fish experiencing fluctuating temperatures had a longer median lifespan but reached smaller asymptotic body size. Within-treatment variation indicated that extended lifespan in fluctuating temperatures was not causally linked to decreased growth rate or smaller body size, but occurred solely due to the effect of thermal fluctuations. Male body size was positively associated with lifespan in stable temperatures but this relationship was disrupted in fluctuating thermal regimes. Females exposed to fluctuating temperatures effectively compensated egg production for their smaller size. Thus, there was no difference in absolute fecundity between thermal regimes and body-size corrected fecundity was higher in females in fluctuating temperatures. Overall, despite a brief exposure to sub-optimal thermal conditions during fluctuations, fluctuating temperature had a positive effect on survival and reproduction. These results suggest that the expression of life history traits and their associations under stable temperatures are a poor representation of the relationships obtained from ecologically relevant thermal fluctuations.

• MeSH
• dlouhověkost MeSH
• Fundulidae * MeSH
• lidé MeSH
• longitudinální studie MeSH
• rozmnožování MeSH
• teplota MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We used a field experiment to test the effects of population density on the growth rate and survival of Austrolebias bellottii, a Neotropical annual killifish. Effects differed between the sexes: males at high densities achieved a smaller final size and experienced higher mortality while no such effects were observed in females. This sex-specific effect could be an indirect consequence of mate competition.

• MeSH
• Fundulidae růst a vývoj   fyziologie   MeSH
• hustota populace MeSH
• rozmnožování MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Nothobranchius fishes (Cyprinodontiformes), known for their genetically encoded extremely compressed lifespan, are considered an excellent vertebrate model for the research of aging. Unlike the rapid accumulation of data concerning their biology, ecology and genome, knowledge of their age-related diseases, including tumours, is still very limited. This Note reports spontaneous neoplastic lesions in the swim bladder gas glands of Nothobranchius furzeri, N. kadleci and N. orthonotus. Based on light and transmission electron microscopy, the neoplastic proliferation of gas gland cells was classified as adenocarcinoma. There was a concurrent proliferation of haemopoietic cells in the kidney interstitium in all individuals diagnosed with this type of primary neoplasia.

• MeSH
• adenokarcinom * veterinární   MeSH
• Cyprinodontiformes * MeSH
• dlouhověkost MeSH
• stárnutí MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: African annual killifishes (Nothobranchius spp.) are adapted to seasonally desiccating habitats (ephemeral pools), surviving dry periods as dormant eggs. Given their peculiar life history, geographic aspects of their diversity uniquely combine patterns typical for freshwater taxa (river basin structure and elevation gradient) and terrestrial animals (rivers acting as major dispersal barriers). However, our current knowledge on fine-scale inter-specific and intra-specific genetic diversity of African annual fish is limited to a single, particularly dry region of their distribution (subtropical Mozambique). Using a widespread annual killifish from coastal Tanzania and Kenya, we tested whether the same pattern of genetic divergence pertains to a wet equatorial region in the centre of Nothobranchius distribution. RESULTS: In populations of Nothobranchius melanospilus species group across its range, we genotyped a part of mitochondrial cytochrome oxidase subunit 1 (COI) gene (83 individuals from 22 populations) and 10 nuclear microsatellite markers (251 individuals from 16 populations). We found five lineages with a clear phylogeographic structure but frequent secondary contact. Mitochondrial lineages were largely congruent with main population genetic clusters identified on microsatellite markers. In the upper Wami basin, populations are isolated as a putative Nothobranchius prognathus, but include also a population from a periphery of the middle Ruvu basin. Other four lineages (including putative Nothobranchius kwalensis) coexisted in secondary contact zones, but possessed clear spatial pattern. Main river channels did not form apparent barriers to dispersal. The most widespread lineage had strong signal of recent population expansion. CONCLUSIONS: We conclude that dispersal of a Nothobranchius species from a wet part of the genus distribution (tropical lowland) is not constrained by main river channels and closely related lineages frequently coexist in secondary contact zones. We also demonstrate contemporary connection between the Ruvu and Rufiji river basins. Our data do not provide genetic support for existence of recently described cryptic species from N. melanospilus complex, but cannot resolve this issue.

• MeSH
• Cyprinodontidae genetika   MeSH
• ekosystém * MeSH
• fylogeneze MeSH
• fylogeografie MeSH
• genetická variace * MeSH
• genetický drift MeSH
• mikrosatelitní repetice MeSH
• mitochondriální DNA genetika   MeSH
• populační genetika MeSH
• řeky MeSH
• respirační komplex IV genetika   MeSH
• sladká voda MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Tanzanie MeSH

Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information-processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large-brained females have a higher overall number of neurons than small-brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.

• MeSH
• biologická evoluce MeSH
• kognice MeSH
• modely neurologické MeSH
• mozek fyziologie   MeSH
• neurony fyziologie   MeSH
• selekce (genetika) * MeSH
• velikost orgánu MeSH
• živorodka genetika   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Strigeid trematodes of the genus Apatemon Szidat, 1928 are intestinal parasites of fish-eating birds, utilizing various fish species as second intermediate hosts. In this study, we report morphometrical and molecular characterization of Apatemon sp. metacercariae parasitizing killifish Nothobranchius furzeri (Cyprinodontiformes: Nothobranchiidae) in south-east Mozambique. Metacercariae obtained from the cerebral cavity of killifish and two adult individuals isolated from experimentally infected ducklings were used for detailed morphological and molecular description, both resulting in generic affiliation to Apatemon. This is the first molecularly confirmed record of this trematode genus in Africa. Considering the morphological variability and wide host range of individual Apatemon species, the combination of both morphological and molecular analyses is indispensable for valid identification of this parasite. The results of our molecular analysis together with phylogenetic reconstruction indicated the presence of a new African lineage, reflecting potentially high diversity within the genus Apatemon comparable with other digenean genera.

• MeSH
• Cyprinodontiformes * MeSH
• geny helmintů MeSH
• infekce červy třídy Trematoda parazitologie   veterinární   MeSH
• metacerkárie anatomie a histologie   klasifikace   genetika   růst a vývoj   MeSH
• multigenová rodina MeSH
• nemoci ryb parazitologie   MeSH
• proteiny červů analýza   MeSH
• respirační komplex IV analýza   MeSH
• RNA helmintů analýza   MeSH
• Trematoda anatomie a histologie   klasifikace   genetika   růst a vývoj   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Mosambik MeSH

• MeSH
• Fundulidae * MeSH
• fyziologická adaptace MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

To uncover the selective forces shaping life-history trait evolution across species, we investigate the genomic basis underlying adaptations to seasonal habitat desiccation in African killifishes, identifying the genetic variants associated with positive and relaxed purifying selection in 45 killifish species and 231 wild individuals distributed throughout sub-Saharan Africa. In annual species, genetic drift led to the expansion of nuclear and mitochondrial genomes and caused the accumulation of deleterious genetic variants in key life-history modulating genes such as mtor, insr, ampk, foxo3, and polg. Relaxation of purifying selection is also significantly associated with mitochondrial function and aging in human populations. We find that relaxation of purifying selection prominently shapes genomes and is a prime candidate force molding the evolution of lifespan and the distribution of genetic variants associated with late-onset diseases in different species. VIDEO ABSTRACT.

• MeSH
• Cyprinodontidae klasifikace   genetika   MeSH
• dlouhověkost * MeSH
• frekvence genu MeSH
• fylogeneze MeSH
• fylogeografie MeSH
• genom mitochondriální MeSH
• mitochondrie genetika   metabolismus   MeSH
• molekulární evoluce MeSH
• mutace MeSH
• replikace DNA MeSH
• selekce (genetika) * MeSH
• stárnutí MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We tested the effect of population density on maximum body size in three sympatric species of annual killifishes Nothobranchius spp. from African ephemeral pools. We found a clear negative effect of population density on body size, limiting their capacity for extremely fast development and rapid growth. This suggests that density-dependent population regulation and the ephemeral character of their habitat impose contrasting selective pressures on the life history of annual killifishes.

• MeSH
• Cyprinodontiformes růst a vývoj   MeSH
• ekosystém MeSH
• Fundulidae růst a vývoj   fyziologie   MeSH
• hustota populace MeSH
• roční období MeSH
• sexuální faktory MeSH
• věkové rozložení MeSH
• velikost těla * fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Afrika MeSH
• Mosambik MeSH