Hormonal and thermal induction of sex reversal in the bearded dragon (Pogona vitticeps, Agamidae)

Ehl, Jan; Vukić, Jasna; Kratochvíl, Lukáš

doi:10.1016/j.jcz.2017.11.002

Cited by 6 publications

(7 citation statements)

References 35 publications

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“…This species became a popular pet worldwide [Cogger, 1992;De Vosjoli et al, 2016]. During a genetic screening of captive bred central bearded dragons and the previous experiment with sex-reversed individuals [Ehl et al, 2017], we uncovered a male with a mismatch between the phenotypic sex and the genotype: it possessed a female-specific allele in the locus assigned as 'contig C' by Quinn et al [2010], serving as a sex-specific PCR marker previously used for detection of sex-reversed individuals in this species [Quinn et al, 2010;Holleley et al, 2015;Ehl et al, 2017;Castelli et al, 2020]. The W-specific fragment represents an anonymous sequence which differs in 4 single nucleotide polymorphisms (SNPs) from the homologous Z-linked locus [Quinn et al, 2010].…”

Section: Methodsmentioning

confidence: 99%

“…We mated the male with the PCR W-linked fragment (the genotype assigned further as ZW m , W m indicates male W-like chromosome) with 3 unrelated females. One of the females possessed the typical ZW genotype, the other 2 females were sex reversed (ZZ sex chromosomes) by the high incubation temperature of 35.5°C [Ehl et al, 2017]. Eggs from these crosses were incubated at the constant temperature of 28°C, the standard incubation temperature which does not lead to thermally-induced sex reversal [Quinn et al, 2010;Holleley et al, 2015;Ehl et al, 2017].…”

Section: Experimental Crossesmentioning

confidence: 99%

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With or Without W? Molecular and Cytogenetic Markers are Not Sufficient for Identification of Environmentally-Induced Sex Reversal in the Bearded Dragon

Ehl

Altmanová

Kratochvíl

2021

Sex Dev

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Transitions from environmental sex determination (ESD) to genotypic sex determination (GSD) require an intermediate step of sex reversal, i.e., the production of individuals with a mismatch between the ancestral genotypic and the phenotypic sex. Among amniotes, the sole well-documented transition in this direction was shown in the laboratory in the central bearded dragon, Pogona vitticeps, where very high incubation temperatures led to the production of females with the male-typical (ZZ) genotype. These sex-reversed females then produced offspring whose sex depended on the incubation temperature. Sex-reversed animals identified by molecular and cytogenetic markers were also reported in the field, and their increasing incidence was speculated as a climate warming-driven transition in sex determination. We show that the molecular and cytogenetic markers normally sex-linked in P. vitticeps are also sex-linked in P. henrylawsoni and P. minor, which points to quite ancient sex chromosomes in this lineage. Nevertheless, we demonstrate, based on a crossing experiment with a male bearded dragon who possesses a mismatch between phenotypic sex and genotype, that the used cytogenetic and molecular markers might not be reliable for the identification of sex reversal. Sex reversal should not be considered as the only mechanism causing a mismatch between genetic sex-linked markers and phenotypic sex, which can emerge also by other processes, here most likely by a rare recombination between regions of sex chromosomes which are normally sex-linked. We warn that sex-linked, even apparently for a long evolutionary time, and sex-specific molecular and cytogenetic markers are not a reliable tool for the identification of sex-reversed individuals in a population and that sex reversal has to be verified by other approaches, particularly by observation of the sex ratio of the progeny.

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Section: Methodsmentioning

confidence: 99%

Section: Experimental Crossesmentioning

confidence: 99%

With or Without W? Molecular and Cytogenetic Markers are Not Sufficient for Identification of Environmentally-Induced Sex Reversal in the Bearded Dragon

Ehl

Altmanová

Kratochvíl

2021

Sex Dev

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“…The norm of reaction with equal sex ratios in non-extreme temperatures itself questions the presence of ESD 31 . Neither of these two studies were able to exclude differential mortality of sexes at certain temperatures (known for example in snakes) 32 or temperature-induced sex reversals (reported in the skink Bassiana duperreyi or dragon lizard Pogona vitticeps ) 33–35 . Moreover, juveniles were sexed by examination of hemipene size (in 15 also by histology, but methodological details and data from histological sections were not presented), which was not validated, e.g., it was not tested whether hemipene size is not phenotypically plastic in relation to temperature.…”

Section: Discussionmentioning

confidence: 99%

Little evidence for switches to environmental sex determination and turnover of sex chromosomes in lacertid lizards

Rovatsos

Vukić

Mrugała

et al. 2019

Sci Rep

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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.

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“…It is unclear what mechanisms are behind the asynchronous internal and external sexual development in squamate TPH, but hormone-related processes likely play an important role. In particular, delayed hormonal secretion could be a main factor in determining TPH of P. vitticeps , as a recent study showed that the estrogen inhibitor fadrozole prevents the hemipenes of P. vitticeps from regressing until after hatching 43 , suggesting that estrogen is required for the formation of the female genital phenotype. Artificial introduction of testosterone in adult female leopard geckoes ( Eublepharis macularius ) induces the formation of hemipenes, demonstrating that the genitalia can be sensitive to endogenous hormones 44 .…”

Section: Discussionmentioning

confidence: 99%

Developmental asynchrony and antagonism of sex determination pathways in a lizard with temperature-induced sex reversal

Whiteley

Weisbecker

Georges

et al. 2018

Sci Rep

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Vertebrate sex differentiation follows a conserved suite of developmental events: the bipotential gonads differentiate and shortly thereafter sex specific traits become dimorphic. However, this may not apply to squamates, a diverse vertebrate lineage comprising of many species with thermosensitive sexual development. Of the three species with data on the relative timing of gonad differentiation and genital dimorphism, the females of two (Niveoscincus ocellatus and Barisia imbricata) exhibit a phase of temporary pseudohermaphroditism or TPH (gonads have differentiated well before genital dimorphism). We report a third example of TPH in Pogona vitticeps, an agamid with temperature-induced male to female sex reversal. These findings suggest that for female squamates, genital and gonad development may not be closely synchronised, so that TPH may be common. We further observed a high frequency of ovotestes, a usually rare gonadal phenotype characterised by a mix of male and female structures, exclusively associated with temperature-induced sex reversal. We propose that ovotestes are evidence of a period of antagonism between male and female sex-determining pathways during sex reversal. Female sexual development in squamates is considerably more complex than has been appreciated, providing numerous avenues for future exploration of the genetic and hormonal cues that govern sexual development.

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Hormonal and thermal induction of sex reversal in the bearded dragon (Pogona vitticeps, Agamidae)

Cited by 6 publications

References 35 publications

With or Without W? Molecular and Cytogenetic Markers are Not Sufficient for Identification of Environmentally-Induced Sex Reversal in the Bearded Dragon

With or Without W? Molecular and Cytogenetic Markers are Not Sufficient for Identification of Environmentally-Induced Sex Reversal in the Bearded Dragon

Little evidence for switches to environmental sex determination and turnover of sex chromosomes in lacertid lizards

Developmental asynchrony and antagonism of sex determination pathways in a lizard with temperature-induced sex reversal

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