Ecotoxicological Perspectives of Sex Determination

Mizoguchi, Beatriz; Valenzuela, Nicole

doi:10.1159/000444770

Cited by 28 publications

(30 citation statements)

References 118 publications

(154 reference statements)

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“…Hormonal manipulation and exposure to exogenous chemicals can cause sex reversal in amphibians with sex chromosomes [Dournon et al, 1990;Orton and Tyler, 2015], and similar manipulations have been conducted with TSD reptiles [Bull et al, 1988;Belaid et al, 2001;Warner and Shine, 2008;Mizoguchi and Valenzuela, 2016] reversing sex from that expected given the temperature of incubation. However, the relevance of these studies to what happens in the wild remains the subject of some conjecture.…”

Section: Definitive Cases Of Environmental Sex Reversal In Wild Reptimentioning

confidence: 99%

Sex Reversal in Reptiles: Reproductive Oddity or Powerful Driver of Evolutionary Change?

Holleley

Sarre²,

O’Meally

et al. 2016

Sex Dev

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Is sex a product of genes, the environment, or both? In this review, we describe the diversity of sex-determining mechanisms in reptiles, with a focus on systems that display gene-environment interactions. We summarise the field and laboratory-based evidence for the occurrence of environmental sex reversal in reptiles and ask whether this is a widespread evolutionary mechanism affecting the evolution of sex chromosomes and speciation in vertebrates. Sex determination systems exist across a continuum of genetic and environmental influences, blurring the lines between what was once considered a strict dichotomy between genetic sex determination and temperature-dependent sex determination. Across this spectrum, we identify the potential for sex reversal in species with clearly differentiated heteromorphic sex chromosomes (Pogona vitticeps, Bassiana duperreyi, Eremias multiocellata, Gekko japonicus), weakly differentiated homomorphic sex chromosomes (Niveoscincus ocellatus), and species with only a weak heritable predisposition for sex (Emys orbicularis, Trachemys scripta). We argue that sex reversal is widespread in reptiles (Testudines, Lacertidae, Agamidae, Scincidae, Gekkonidae) and has the potential to have an impact on individual fitness, resulting in reproductively, morphologically, and behaviourally unique phenotypes. Sex reversal is likely to be a powerful evolutionary force responsible for generating and maintaining lability and diversity in reptile sex-determining modes.

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Section: Definitive Cases Of Environmental Sex Reversal In Wild Reptimentioning

confidence: 99%

Sex Reversal in Reptiles: Reproductive Oddity or Powerful Driver of Evolutionary Change?

Holleley

Sarre²,

O’Meally

et al. 2016

Sex Dev

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“…These other factors include maternal environmental effects like egg size [19] and yolk steroid hormones [20], which appear to reflect differential maternal investment [21,22]. It may therefore not be surprising that several endocrinedisrupting chemicals have also been found to interfere with sex determination in species with TSD [23]. For instance, embryos of the turtle Trachemys scripta that are incubated at male-producing temperatures often turn into females when exposed to oestradiol [24], different types of polychlorinated biphenyls (PCBs) [25], the herbicide atrazine [26] or other compounds of which the insecticide chlordane is synergistic with oestradiol when applied in combination [24].…”

Section: Sex Determination In Disturbed and Undisturbed Environmentsmentioning

confidence: 99%

“…A recent example includes Tamschick et al [35], who found species-specific reaction norms in the response of three amphibians to exposure to EE2. Mizoguchi & Valenzuela [23] discuss possible species-specific reaction norms to various micropollutants in reptiles.…”

Section: Rapid Evolutionary Responses To Environmentally Disturbed Sementioning

confidence: 99%

Demographic and genetic consequences of disturbed sex determination

Wedekind¹

2017

Phil. Trans. R. Soc. B

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During sex determination, genetic and/or environmental factors determine the cascade of processes of gonad development. Many organisms, therefore, have a developmental window in which their sex determination can be sensitive to, for example, unusual temperatures or chemical pollutants. Disturbed environments can distort population sex ratios and may even cause sex reversal in species with genetic sex determination. The resulting genotype-phenotype mismatches can have long-lasting effects on population demography and genetics. I review the theoretical and empirical work in this context and explore in a simple population model the role of the fitness of chromosomally aberrant YY genotypes that are a consequence of environmentally induced feminization. Low is mostly beneficial for population growth. During feminization, low reduces the proportion of genetic males and hence accelerates population growth, especially at low rates of feminization and at high fitness costs of the feminization itself (i.e. when feminization would otherwise not affect population dynamics much). When sex reversal ceases, low mitigates the negative effects of feminization and can even prevent population extinction. Little is known about in natural populations. The available models now need to be parametrized in order to better predict the long-term consequences of disturbed sex determination.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.

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“…Endocrine processes provide the foundation for sex determination and subsequent gonadal formation in all vertebrate species. A growing body of literature advocates that endocrine disruption can overcome the sex-determining program irrespective of GSD or ESD (Mizoguchi and Valenzuela, 2016;Golan and Levavi-Sivan, 2014;Nakamura, 2010). Thyroid hormones (THs) have pleotropic effects in developing vertebrates, including effects on gonadal development.…”

Section: Introductionmentioning

confidence: 99%

Expression of sf1 and dax-1 are regulated by thyroid hormones and androgens during Silurana tropicalis early development

Campbell

Langlois

2018

General and Comparative Endocrinology

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Thyroid hormones (THs) and androgens have been shown to be extensively involved in sexual development; however, relatively little is known with regard to TH-related and androgenic actions in sex determination. We first established expression profiles of three sex-determining genes (sf1, dax-1, and sox9) during the embryonic development of Western clawed frogs (Silurana tropicalis). Transcripts of sf1 and sox9 were detected in embryos before the period in which embryonic transcription commences indicating maternal transfer, whereas dax-1 transcripts were not detected until later in development. To examine whether TH status affects sex-determining gene expression in embryonic S. tropicalis, embryos were exposed to co-treatments of iopanoic acid (IOP), thyroxine (T4), or triiodothyronine (T3) for 96 h. Expression profiles of TH receptors and deiodinases reflect inhibition of peripheral deiodinase activity by IOP and recovery by T3. Relevantly, elevated TH levels significantly increased the expression of sf1 and dax-1 in embryonic S. tropicalis. Further supporting TH-mediated regulation, examination of the presence and frequency of transcription factor binding sites in the putative promoter regions of sex-determining genes in S. tropicalis and rodent and fish models using in silico analysis also identified TH motifs in the putative promoter regions of sf1 and dax-1. Together these findings advocate that TH actions as early as the period of embryogenesis may affect gonadal fate in frogs. Mechanisms of TH and androgenic crosstalk in relation to the regulation of steroid-related gene expression were also investigated.

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Ecotoxicological Perspectives of Sex Determination

Cited by 28 publications

References 118 publications

Sex Reversal in Reptiles: Reproductive Oddity or Powerful Driver of Evolutionary Change?

Sex Reversal in Reptiles: Reproductive Oddity or Powerful Driver of Evolutionary Change?

Demographic and genetic consequences of disturbed sex determination

Expression of sf1 and dax-1 are regulated by thyroid hormones and androgens during Silurana tropicalis early development

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