Studies on sex differentiation and sex determination in amphibians. III. rudimentary hermaphroditism and Y chromosome in Rana temporaria

Witschi, Emil

doi:10.1002/jez.1400540202

Cited by 97 publications

(77 citation statements)

References 4 publications

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“…Similarly, differential mortality is unlikely to have played a role; this would imply mortality to be sex biased in families from Tvedö ra but not from Ammarnäs, and in a very specific way, being biased towards males before metamorphosis, then towards females after metamorphosis. We find more parsimonious the suggestion that offspring from these two populations fit the distinct patterns of gonadal development already documented for this species [16,20,21]. Thus, we tentatively assign Ammarnäs to Witschi's [20] 'differentiated race', in which offspring present either testes or ovaries in equal proportion at metamorphosis, and Tvedö ra to the 'semi-differentiated race', characterized by a female bias at metamorphosis, but also some juveniles already with testes.…”

Section: Discussionsupporting

confidence: 76%

“…[19], appears as a good model to investigate interactions between genes and environment. Its sex-determination system had already raised interest in the early twentieth century, with the description by Witschi [16,20] of 'sex races', correlating with climatic zones. In the so-called 'differentiated race', assigned to boreal and alpine climates, juveniles present equal sex ratios at metamorphosis, with well-differentiated testes or ovaries.…”

Section: Introductionmentioning

confidence: 99%

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Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

et al. 2015

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Sex-chromosome differentiation was recently shown to vary among common frog populations in Fennoscandia, suggesting a trend of increased differentiation with latitude. By rearing families from two contrasted populations (respectively, from northern and southern Sweden), we show this disparity to stem from differences in sex-determination mechanisms rather than in XY-recombination patterns. Offspring from the northern population display equal sex ratios at metamorphosis, with phenotypic sexes that correlate strongly with paternal LG 2 haplotypes (the sex chromosome); accordingly, Y haplotypes are markedly differentiated, with male-specific alleles and depressed diversity testifying to their smaller effective population size. In the southern population, by contrast, a majority of juveniles present ovaries at metamorphosis; only later in development do sex ratios return to equilibrium. Even at these later stages, phenotypic sexes correlate only mildly with paternal LG 2 haplotypes; accordingly, there are no recognizable Y haplotypes. These distinct patterns of gonadal development fit the concept of 'sex races' proposed in the 1930s, with our two populations assigned to the 'differentiated' and 'semi-differentiated' races, respectively. Our results support the suggestion that 'sex races' differ in the genetic versus epigenetic components of sex determination. Analysing populations from the 'undifferentiated race' with high-density genetic maps should help to further test this hypothesis.

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Section: Discussionsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

et al. 2015

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“…Both forms can sometimes exist in a given population [58]. In addition, Witschi [59] observed that in controlled breeding, the parental type is transmitted. In the undifferentiated breeds of the common frog (Rana temporaria), the first hermaphrodites occur about two months after metamorphosis, after which several months are required to have only differentiated individuals.…”

Section: Hynobius Retardatus I [65]mentioning

confidence: 99%

Sex determination: the amphibian models

2004

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-We review and discuss current knowledge about sex determination in amphibians. The astonishing wide variety of mechanisms of genotypic sex determination is presented and discussed in an evolutionary context. We recall the natural occurrence of transitory juvenile hermaphroditism in some species. Our present knowledge of the mechanisms of sex determination in amphibians is compared to that in mammals. The influence of epigenetic factors, and especially temperature is highlighted. In amphibians, the influence of temperature on sexual differentiation, that can prevail over genotypic sex determination, remains poorly considered in publications. We suggest that studies on genetic and epigenetic factors of gonadal sex differentiation in amphibians could provide substantial information on the evolutionary process of sex determination mechanisms in current living vertebrates.sex determination mechanisms / sexual differentiation / hermaphroditism / epigenetic factors

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“…Families from these two populations displayed very similar rates of recombination (very high in females and close to zero in males), hence discarding hypothesis (1). However, patterns of gonadal development among offspring were strikingly dissimilar: Ammarnäs could be assigned to the 'differentiated sex race' (Witschi, 1929(Witschi, , 1930, where most juveniles present already at metamorphosis (Gosner stage 43;Gosner, 1960) either ovaries or testes in equal proportions, whereas Tvedöra belonged to the 'semi-differentiated sex race' where most juveniles present ovaries at this stage; only later in development (around Gosner stage 46) do some of them replace ovaries by testes. Sibship analyses also revealed striking differences in the association between offspring phenotypic sex and paternally inherited LG 2 haplotypes, which was close to perfect in Ammarnäs, but much weaker in Tvedöra (though highly significant overall) and very variable among families (range 0.0-1.0).…”

Section: Introductionmentioning

confidence: 97%

The genetic contribution to sex determination and number of sex chromosomes vary among populations of common frogs (Rana temporaria)

et al. 2016

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The patterns of sex determination and sex differentiation have been shown to differ among geographic populations of common frogs. Notably, the association between phenotypic sex and linkage group 2 (LG 2 ) has been found to be perfect in a northern Swedish population, but weak and variable among families in a southern one. By analyzing these populations with markers from other linkage groups, we bring two new insights: (1) the variance in phenotypic sex not accounted for by LG 2 in the southern population could not be assigned to genetic factors on other linkage groups, suggesting an epigenetic component to sex determination; (2) a second linkage group (LG 7 ) was found to co-segregate with sex and LG 2 in the northern population. Given the very short timeframe since post-glacial colonization (in the order of 1000 generations) and its seemingly localized distribution, this neo-sex chromosome system might be the youngest one described so far. It does not result from a fusion, but more likely from a reciprocal translocation between the original Y chromosome (LG 2 ) and an autosome (LG 7 ), causing their cosegregation during male meiosis. By generating a strict linkage between several important genes from the sex-determination cascade (Dmrt1, Amh and Amhr2), this neo-sex chromosome possibly contributes to the 'differentiated sex race' syndrome (strictly genetic sex determination and early gonadal development) that characterizes this northern population.

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Studies on sex differentiation and sex determination in amphibians. III. rudimentary hermaphroditism and Y chromosome in Rana temporaria

Cited by 97 publications

References 4 publications

Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

Sex-chromosome differentiation and ‘sex races’ in the common frog ( Rana temporaria )

Sex determination: the amphibian models

The genetic contribution to sex determination and number of sex chromosomes vary among populations of common frogs (Rana temporaria)

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