Amniotes possess variability in sex determination, from environmental sex determination (ESD), where no sex chromosomes are present, to genotypic sex determination (GSD) with highly differentiated sex chromosomes. Some evolutionary scenarios postulate high stability of differentiated sex chromosomes and rare transitions from GSD to ESD. However, sex chromosome turnovers and two independent transitions from highly differentiated ZZ/ZW sex chromosomes to ESD were previously reported in the lacertid lizards. Here, we examined the homology of sex chromosomes in the wide phylogenetic spectrum of lacertids and their outgroups by comparing gene copy numbers between sexes in genes previously found to be Z-specific in some lacertids. Our current sampling covers 45 species from 26 genera including lineages supposed to possess a derived sex determining systems. We found that all tested lacertids share homologous differentiated ZZ/ZW sex chromosomes, which were present already in their common ancestor living around 85 million years ago. These differentiated sex chromosomes are not present in amphisbaenians and teiid lizards, the close relatives of lacertids. Our study demonstrates how inaccuracies in data can influence the outcome of phylogenetic reconstructions of evolution of sex determination, in this case they overestimated the number of shifts from GSD to ESD and the rate in turnovers of sex chromosomes.
- MeSH
- cytogenetika statistika a číselné údaje MeSH
- fylogeneze MeSH
- genotyp * MeSH
- genová dávka MeSH
- ještěři fyziologie MeSH
- molekulární evoluce MeSH
- pohlavní chromozomy genetika MeSH
- procesy určující pohlaví fyziologie MeSH
- sekvenční homologie nukleových kyselin MeSH
- správnost dat MeSH
- vystavení vlivu životního prostředí * MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- diagnostické zobrazování metody MeSH
- gonadální dysgeneze * MeSH
- karyotypizace metody MeSH
- lidé MeSH
- nedoslýchavost MeSH
- novorozenec nedonošený * MeSH
- novorozenec MeSH
- poruchy sexuálního vývoje MeSH
- procesy určující pohlaví fyziologie MeSH
- sexuální diferenciace fyziologie MeSH
- Check Tag
- lidé MeSH
- novorozenec MeSH
- Publikační typ
- kazuistiky MeSH
Amniote vertebrates, the group consisting of mammals and reptiles including birds, possess various mechanisms of sex determination. Under environmental sex determination (ESD), the sex of individuals depends on the environmental conditions occurring during their development and therefore there are no sexual differences present in their genotypes. Alternatively, through the mode of genotypic sex determination (GSD), sex is determined by a sex-specific genotype, i.e. by the combination of sex chromosomes at various stages of differentiation at conception. As well as influencing sex determination, sex-specific parts of genomes may, and often do, develop specific reproductive or ecological roles in their bearers. Accordingly, an individual with a mismatch between phenotypic (gonadal) and genotypic sex, for example an individual sex-reversed by environmental effects, should have a lower fitness due to the lack of specialized, sex-specific parts of their genome. In this case, evolutionary transitions from GSD to ESD should be less likely than transitions in the opposite direction. This prediction contrasts with the view that GSD was the ancestral sex-determining mechanism for amniote vertebrates. Ancestral GSD would require several transitions from GSD to ESD associated with an independent dedifferentiation of sex chromosomes, at least in the ancestors of crocodiles, turtles, and lepidosaurs (tuataras and squamate reptiles). In this review, we argue that the alternative theory postulating ESD as ancestral in amniotes is more parsimonious and is largely concordant with the theoretical expectations and current knowledge of the phylogenetic distribution and homology of sex-determining mechanisms.
- MeSH
- biologická evoluce * MeSH
- obratlovci genetika fyziologie MeSH
- pohlavní chromozomy genetika MeSH
- procesy určující pohlaví genetika fyziologie MeSH
- životní prostředí MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Previous work on lizards has shown that many sexually dimorphic traits depend on testosterone (T), but the details of this control can vary among species. Here, we tested the role of T on the expression of morphological, physiological, and behavioral traits in Lichtenfelder's gecko (Goniurosaurus lichtenfelderi), from the lizard family Eublepharidae notable for interspecific variation in sexually dimorphic traits and the mode of sex determination. Experiments included three groups of males (intact control, surgically castrated, castrated with T replacement) and two groups of females (intact control, T supplemented). In males, castration caused reductions in 1) the size of hemipenes, 2) offensive aggression, 3) male sexual behavior in a neutral arena, 4) activity of precloacal glands, and 5) loss of male chemical cues for sex recognition. These reductions were not observed in castrated males with T replacement. Interestingly, castrated males performed sexual behavior in their home cages, which shows that the effect of T depends on the environmental context. Notably, tail vibration, previously reported as a courtship behavior in other eublepharids, is displayed by males of G. lichtenfelderi during interactions with conspecifics of both sexes, suggesting an evolutionary shift in the meaning of this signal. In females, T induced growth of hemipenes and male-typical courtship but did not induce precloacal pore activity, aggression, or mounting. In comparison to previous reports on Eublepharis macularius, our results indicate that effects of T do not depend on the mode of sex determination. Further, our results extend our understanding of the complexity of control of male traits and illustrate how lability in the effects of T can be a general mechanism causing evolutionary changes in the components of suites of functionally correlated traits.
- MeSH
- agrese fyziologie MeSH
- androgeny farmakologie fyziologie MeSH
- ještěři fyziologie MeSH
- kastrace MeSH
- námluvy MeSH
- pohlavní dimorfismus MeSH
- procesy určující pohlaví účinky léků fyziologie MeSH
- sexuální chování zvířat účinky léků fyziologie MeSH
- sexuální faktory MeSH
- testosteron farmakologie fyziologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
A wide variety of sex determination systems exist among squamate reptiles. They can therefore serve as an important model for studies of evolutionary transitions among particular sex determination systems. However, we still have only a limited knowledge of sex determination in certain important lineages of squamates. In this respect, one of the most understudied groups is the family Helodermatidae (Anguimorpha) encompassing the only two venomous species of lizards which are potentially lethal to human beings. We uncovered homomorphic ZZ/ZW sex chromosomes in the Gila monster (Heloderma suspectum) with a highly heterochromatic W chromosome. The sex chromosomes are morphologically similar to the ZZ/ZW sex chromosomes of monitor lizards (Varanidae). If the sex chromosomes of helodermatids and varanids are homologous, female heterogamety may be ancestral for the whole Anguimorpha group. Moreover, we found that the karyotype of the Gila monster consists of 2n = 36 chromosomes (14 larger metacentric chromosomes and 22 acrocentric microchromosomes). 2n = 36 is the widely distributed chromosomal number among squamates. In his pioneering works representing the only previous cytogenetic examination of the family Helodermatidae, Matthey reported the karyotype as 2n = 38 and suggested a different chromosomal morphology for this species. We believe that this was probably erroneously. We also discovered a strong accumulation of telomeric sequences on several pairs of microchromosomes in the Gila monster, which is a trait documented relatively rarely in vertebrates. These new data fill an important gap in our understanding of the sex determination and karyotype evolution of squamates.
- MeSH
- hybridizace in situ MeSH
- ještěři genetika fyziologie MeSH
- karyotypizace MeSH
- mitochondriální DNA genetika MeSH
- počítačové zpracování obrazu MeSH
- pohlavní chromozomy genetika MeSH
- procesy určující pohlaví genetika fyziologie MeSH
- srovnávací genomová hybridizace MeSH
- taxonomické DNA čárové kódování MeSH
- výpočetní biologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- diagnostické techniky endokrinologické MeSH
- hypogonadismus diagnóza krev MeSH
- klinická chemie * metody MeSH
- kongenitální adrenální hyperplazie diagnóza krev moč MeSH
- lidé MeSH
- menstruační poruchy diagnóza krev MeSH
- nemoci endokrinního systému * diagnóza MeSH
- ovarium fyziologie MeSH
- ovotestikulární poruchy sexuálního vývoje diagnóza MeSH
- pohlavní hormony krev MeSH
- poruchy sexuálního vývoje * diagnóza MeSH
- procesy určující pohlaví fyziologie MeSH
- spermatogeneze fyziologie MeSH
- steroidy metabolismus MeSH
- systém hypofýza - nadledviny fyziologie MeSH
- systém hypotalamus-hypofýza fyziologie MeSH
- testis fyziologie MeSH
- testosteron krev metabolismus MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
