scholarly journals The behavioural consequences of sex reversal in dragons

2016 ◽  
Vol 283 (1832) ◽  
pp. 20160217 ◽  
Author(s):  
Hong Li ◽  
Clare E. Holleley ◽  
Melanie Elphick ◽  
Arthur Georges ◽  
Richard Shine
Keyword(s):  
Natural Populations ◽  
Tail Length ◽  
Sex Reversal ◽  
Activity Level ◽  
Lizard Species ◽  
General Behaviour ◽  
Thermally Induced ◽  
Individual Fitness ◽  
Pogona Vitticeps ◽  
Incubation Temperatures

Sex differences in morphology, physiology, and behaviour are caused by sex-linked genes, as well as by circulating sex-steroid levels. Thus, a shift from genotypic to environmental sex determination may create an organism that exhibits a mixture of male-like and female-like traits. We studied a lizard species (Central Bearded Dragon, Pogona vitticeps ), in which the high-temperature incubation of eggs transforms genetically male individuals into functional females. Although they are reproductively female, sex-reversed dragons (individuals with ZZ genotype reversed to female phenotype) resemble genetic males rather than females in morphology (relative tail length), general behaviour (boldness and activity level), and thermoregulatory tactics. Indeed, sex-reversed ‘females’ are more male-like in some behavioural traits than are genetic males. This novel phenotype may impose strong selection on the frequency of sex reversal within natural populations, facilitating rapid shifts in sex-determining systems. A single period of high incubation temperatures (generating thermally induced sex reversal) can produce functionally female individuals with male-like (or novel) traits that enhance individual fitness, allowing the new temperature-dependent sex-determining system to rapidly replace the previous genetically based one.

scholarly journals Developmental dynamics of sex reprogramming by high incubation temperatures in a dragon lizard

2021 ◽  
Author(s):  
Sarah L Whiteley ◽  
Clare E Holleley ◽  
Arthur Georges
Keyword(s):  
Developmental Stages ◽  
Sex Reversal ◽  
Transcriptional Level ◽  
Vertebrate Species ◽  
Gene Environment ◽  
Bearded Dragon ◽  
Pogona Vitticeps ◽  
Incubation Temperatures ◽  
Developmental Dynamics ◽  
Male To Female

In some vertebrate species, gene-environment interactions can determine sex, driving bipotential gonads to differentiate into either ovaries or testes. In the central bearded dragon (Pogona vitticeps), the genetic influence of sex chromosomes (ZZ/ZW) can be overridden by high incubation temperatures, causing ZZ male to female sex reversal. Previous research showed ovotestes, a rare gonadal phenotype with traits of both sexes, develop during sex reversal, leading to the hypothesis that sex reversal relies on high temperature feminisation to outcompete the male genetic cue. To test this, we conducted temperature switching experiments at key developmental stages, and analysed the effect on gonadal phenotypes using histology and transcriptomics. We found sexual fate is more strongly influenced by the ZZ genotype than temperature. Any exposure to low temperatures (28oC) caused testes differentiation, whereas sex reversal required longer exposure to high temperatures. We revealed ovotestes exist along a spectrum of female-ness to male-ness at the transcriptional level. We found inter-individual variation in gene expression changes following temperature switches, suggesting both genetic sensitivity to, and the timing and duration of the temperature cue influences sex reversal. These findings bring new insights to the mechanisms underlying sex reversal, improving our understanding of thermosensitive sex systems in vertebrates.

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

2021 ◽  
pp. 1-10
Author(s):  
Jan Ehl ◽  
Marie Altmanová ◽  
Lukáš Kratochvíl
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Incubation Temperature ◽  
Sex Reversal ◽  
Intermediate Step ◽  
Crossing Experiment ◽  
Bearded Dragon ◽  
Genotypic Sex Determination ◽  
Pogona Vitticeps ◽  
Incubation Temperatures

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.

scholarly journals Sex Differentiation in Amphibians: Effect of Temperature and Its Influence on Sex Reversal

2021 ◽  
pp. 1-11
Author(s):  
Adrián Ruiz-García ◽  
Álvaro S. Roco ◽  
Mónica Bullejos
Keyword(s):  
Sexual Differentiation ◽  
Sex Differentiation ◽  
Environmental Contaminants ◽  
Natural Populations ◽  
Sex Reversal ◽  
The Other ◽  
Effect Of Temperature ◽  
Amphibian Species ◽  
Expected Increase

The role of environmental factors in sexual differentiation in amphibians is not new. The effect of hormones or hormone-like compounds is widely demonstrated. However, the effect of temperature has traditionally been regarded as something anecdotal that occurs in extreme situations and not as a factor to be considered. The data currently available reveal a different situation. Sexual differentiation in some amphibian species can be altered even by small changes in temperature. On the other hand, although not proven, it is possible that temperature is related to the appearance of sex-reversed individuals in natural populations under conditions unrelated to environmental contaminants. According to this, temperature, through sex reversal (phenotypic sex opposed to genetic sex), could play an important role in the turnover of sex-determining genes and in the maintenance of homomorphic sex chromosomes in this group. Accordingly, and given the expected increase in global temperatures, growth and sexual differentiation in amphibians could easily be affected, altering the sex ratio in natural populations and posing major conservation challenges for a group in worldwide decline. It is therefore particularly urgent to understand the mechanism by which temperature affects sexual differentiation in amphibians.

Dynamics of epigenetic modifiers and environmentally sensitive proteins in a reptile with temperature induced sex reversal

2021 ◽  
Author(s):  
Sarah Whiteley ◽  
Robert D McCuaig ◽  
Clare E Holleley ◽  
Sudha Rao ◽  
Arthur Georges
Keyword(s):  
Sex Reversal ◽  
Molecular Characteristics ◽  
Environmental Response ◽  
Specific Expression ◽  
Epigenetic Modifiers ◽  
Cellular Localisation ◽  
Reptile Species ◽  
Environmentally Sensitive ◽  
Pogona Vitticeps

Abstract The mechanisms by which sex is determined, and how a sexual phenotype is stably maintained during adulthood, has been the focus of vigorous scientific inquiry. Resources common to the biomedical field (automated staining and imaging platforms) were leveraged to provide the first immunofluorescent data for a reptile species with temperature induced sex reversal. Two four-plex immunofluorescent panels were explored across three sex classes (sex reversed ZZf females, normal ZWf females, and normal ZZm males). One panel was stained for chromatin remodelling genes JARID2 and KDM6B, and methylation marks H3K27me3, and H3K4me3 (Jumonji Panel). The other CaRe panel stained for environmental response genes CIRBP and RelA, and H3K27me3 and H3K4me3. Our study characterised tissue specific expression and cellular localisation patterns of these proteins and histone marks, providing new insights to the molecular characteristics of adult gonads in a dragon lizard Pogona vitticeps. The confirmation that mammalian antibodies cross react in P. vitticeps paves the way for experiments that can take advantage of this new immunohistochemical resource to gain a new understanding of the role of these proteins during embryonic development, and most importantly for P. vitticeps, the molecular underpinnings of sex reversal.

Sex-ratio meiotic drive in Drosophila simulans: cellular mechanism, candidate genes and evolution

2006 ◽  
Vol 34 (4) ◽  
pp. 562-565 ◽  
Author(s):  
C. Montchamp-Moreau
Keyword(s):  
Sex Ratio ◽  
X Chromosome ◽  
Natural Populations ◽  
Meiotic Drive ◽  
Female Offspring ◽  
Drosophila Simulans ◽  
X Chromosomes ◽  
Individual Fitness ◽  
Primary Sex Ratio ◽  
Intragenomic Conflict

The sex-ratio trait, reported in a dozen Drosophila species, is a type of naturally occurring meiotic drive in which the driving elements are located on the X chromosome. Typically, as the result of a shortage of Y-bearing spermatozoa, males carrying a sex-ratio X chromosome produce a large excess of female offspring. The presence of sex-ratio chromosomes in a species can have considerable evolutionary consequences, because they can affect individual fitness and trigger extended intragenomic conflict. Here, I present the main results of the study performed in Drosophila simulans. In this species, the loss of Y-bearing spermatozoa is related to the inability of the Y chromosome sister-chromatids to separate properly during meiosis II. Fine genetic mapping has shown that the primary sex-ratio locus on the X chromosome contains two distorter elements acting synergistically, both of which are required for drive expression. One element has been genetically mapped to a tandem duplication. To infer the natural history of the trait, the pattern of DNA sequence polymorphism in the surrounding chromosomal region is being analysed in natural populations of D. simulans harbouring sex-ratio X chromosomes. Initial results have revealed the recent spread of a distorter allele.

Sex differences in optimal incubation temperatures in a scincid lizard species

Oecologia ◽  
1999 ◽  
Vol 118 (4) ◽  
pp. 431-437 ◽  
Author(s):  
Melanie J. Elphick ◽  
Richard Shine
Keyword(s):  
Sex Differences ◽  
Lizard Species ◽  
Incubation Temperatures ◽  
Optimal Incubation

scholarly journals Incubation under climate warming affects learning ability and survival in hatchling lizards

2017 ◽  
Vol 13 (3) ◽  
pp. 20170002 ◽  
Author(s):  
Buddhi Dayananda ◽  
Jonathan K. Webb
Keyword(s):  
Spatial Learning ◽  
Climate Warming ◽  
Cognitive Abilities ◽  
Incubation Temperature ◽  
Learning Ability ◽  
Lizard Species ◽  
Southeastern Australia ◽  
Temperature Regimes ◽  
In The Wild ◽  
Incubation Temperatures

Despite compelling evidence for substantial individual differences in cognitive performance, it is unclear whether cognitive ability influences fitness of wild animals. In many animals, environmental stressors experienced in utero can produce substantial variation in the cognitive abilities of offspring. In reptiles, incubation temperatures experienced by embryos can influence hatchling brain function and learning ability. Under climate warming, the eggs of some lizard species may experience higher temperatures, which could affect the cognitive abilities of hatchlings. Whether such changes in cognitive abilities influence the survival of hatchlings is unknown. To determine whether incubation-induced changes in spatial learning ability affect hatchling survival, we incubated velvet gecko, Amalosia lesueurii , eggs using two fluctuating temperature regimes to mimic current (cold) versus future (hot) nest temperatures. We measured the spatial learning ability of hatchlings from each treatment, and released individually marked animals at two field sites in southeastern Australia. Hatchlings from hot-incubated eggs were slower learners than hatchlings from cold-incubated eggs. Survival analyses revealed that hatchlings with higher learning scores had higher survival than hatchlings with poor learning scores. Our results show that incubation temperature affects spatial learning ability in hatchling lizards, and that such changes can influence the survival of hatchlings in the wild.

scholarly journals Characterization of Metarhizium viride Mycosis in Veiled Chameleons (Chamaeleo calyptratus), Panther Chameleons (Furcifer pardalis), and Inland Bearded Dragons (Pogona vitticeps)

2016 ◽  
Vol 55 (3) ◽  
pp. 832-843 ◽  
Author(s):  
Volker Schmidt ◽  
Linus Klasen ◽  
Juliane Schneider ◽  
Jens Hübel ◽  
Michael Pees
Keyword(s):  
Sequence Analysis ◽  
Large Subunit ◽  
Antifungal Susceptibility ◽  
Clinical Signs ◽  
Antifungal Drugs ◽  
Lizard Species ◽  
Internal Transcribed Spacer Region ◽  
Content Type ◽  
Pogona Vitticeps ◽  
Chamaeleo Calyptratus

ABSTRACT Metarhizium viride has been associated with fatal systemic mycoses in chameleons, but subsequent data on mycoses caused by this fungus in reptiles are lacking. The aim of this investigation was therefore to obtain information on the presence of M. viride in reptiles kept as pets in captivity and its association with clinical signs and pathological findings as well as improvement of diagnostic procedures. Beside 18S ribosomal DNA (rDNA) (small subunit [SSU]) and internal transcribed spacer region 1 (ITS-1), a fragment of the large subunit (LSU) of 28S rDNA, including domain 1 (D1) and D2, was sequenced for the identification of the fungus and phylogenetic analysis. Cultural isolation and histopathological examinations as well as the pattern of antifungal drug resistance, determined by using agar diffusion testing, were additionally used for comparison of the isolates. In total, 20 isolates from eight inland bearded dragons ( Pogona vitticeps ), six veiled chameleons ( Chamaeleo calyptratus ), and six panther chameleons ( Furcifer pardalis ) were examined. Most of the lizards suffered from fungal glossitis, stomatitis, and pharyngitis or died due to visceral mycosis. Treatment with different antifungal drugs according to resistance patterns in all three different lizard species was unsuccessful. Sequence analysis resulted in four different genotypes of M. viride based on differences in the LSU fragment, whereas the SSU and ITS-1 were identical in all isolates. Sequence analysis of the SSU fragment revealed the first presentation of a valid large fragment of the SSU of M. viride . According to statistical analysis, genotypes did not correlate with differences in pathogenicity, antifungal susceptibility, or species specificity.

Size-dependent pigmentation-pattern formation in embryos of Alligator mississippiensis : time of initiation of pattern generation mechanism

1990 ◽  
Vol 239 (1296) ◽  
pp. 279-293 ◽  
Keyword(s):  
Pattern Formation ◽  
Incubation Temperature ◽  
Cell Movement ◽  
Tail Length ◽  
Dorsal Side ◽  
Pattern Generation ◽  
Alligator Mississippiensis ◽  
Pigmentation Pattern ◽  
Size Dependent ◽  
Incubation Temperatures

The pigmentation pattern of Alligator mississippiensis was examined. The number of white stripes on the dorsal side of embryos (stages 21–28) and hatchlings from eggs incubated at 30°C (100% females) and 33°C (100% males) was recorded. Total length, nape–rump length and tail length were recorded for each embryo and hatchling. The number of white stripes was affected by incubation temperature but not sex ; hatchlings incubated a t 33°C had two more white stripes than those at 30°C, despite being the same length. Five female hatchlings produced at 33°C by manipulation of the temperature, had the same number of stripes as males that developed under the same incubation temperatures. The appearance of the pigmentation was accelerated in embryos incubated at 33°C, occurring eight days earlier than at 30°C. At the time just before the first signs of pigment deposition, embryos from 33°C were longer than those at 30°C. If the stripe formation is size dependent this explains why hatchlings at 33°C have more stripes than hatchlings from 30°C. The mechanism that produces the stripe patterns is unknown. We describe key elements a pattern formation mechanism must possess to produce such stripes and suggest a possible mechanism, based on cell movement driven by chemotaxis. We apply the mathematical model to dorsal patterning on A . mississippiensis . We show how length at pattern formation is the prime factor in determining stripe number and how the pattern can be formed in the observed anterior–posterior sequence. We present numerical simulations and show that the qualitative behaviour is consistent with the experimental results.

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