The Relative Effectiveness of Estrone, Estradiol-17β, and Estriol in Sex Reversal in the Red-Eared Slider (Trachemys scripta), a Turtle with Temperature-Dependent Sex Determination

Crews, David; Cantu, Amador R.; Rhen, Turk; Vohra, Rais

doi:10.1006/gcen.1996.0075

Cited by 48 publications

(39 citation statements)

References 6 publications

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“…Overall, the results for single hormone treatments were similar to those determined for the same estrogens at the same temperature in a previous study (23). Sex reversal occurred in a dose-dependent manner with each estrogen alone (Fig.…”

Section: Resultssupporting

confidence: 87%

“…This difference was clearly evident when comparing the dosage at which 50% of the embryos were sex reversed. Sex ratio data for the estrone dosage of 0.4 pg was discarded, as the value was an outlier [the observed sex ratio was too low in comparison with the pattern displayed in the current data set and the expected sex ratio based on Crews et al (23)]. …”

Section: Resultsmentioning

confidence: 99%

“…Although there is some hypertrophy of oviducts following exposure to estriol or to high doses of 17,-estradiol (estradiol), the ovaries of hormone-determined females are indistinguishable from the ovaries of temperature-determined females (22,23). Likewise, the testes of hormone-determined males appear normal even though the phallus is overly developed in dihydrotestosteronetreated turtles (18).…”

mentioning

confidence: 99%

“…In addition, the steroidal estrogens estrone, estradiol, and estriol have strong dosage effects that synergize with incubation temperature to induce ovarian differentiation. The potency of these estrogens changes with increasing temperature such that estriol is much more potent than estradiol and estrone at a male-producing incubation temperature, and estrone becomes as potent as estriol with increasing temperature (23). Synergy also occurs between certain hydroxylated PCBs (4).…”

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confidence: 99%

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Developmental synergism of steroidal estrogens in sex determination.

Bergeron

Willingham

Osborn

et al. 1999

Environ Health Perspect

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Gonadal sex in the red-wared slider turtle, Trachemys scdpta, is determined by incubation temperature during embryonic development Evidence suggests that temperature determines sex by influencing steroid hormone metabolism and/or sensitivity: steroidogenic enzyme inhibitors or exogenous sex steroid hormones and their man-made analogs override (or enhance) temperature effects on sex determination. Specificlly, nonaromatizable androgens and aromatase inhibitors induce testis dif tiain at female-producing temperatures, whereas aromatizable androgens and estrogens induce ovary differentiation at male-producing temperatures. Moreover, natural estrogens and temperature synergize to produce more feiales than would be expected ifestrogens and temperaure had purely addiie eflects on sex determination. In this study, we use sex reversal of turtle embryos incubated at a male-producing temperature to examine synergism among steroidal estrogens: estrone, 17JB-estradiol, and estriol. A low dose of 171-estradiol (200 ng) showed significant synergism when administered with a single low dose of estriol (10 ng [Online 8 January 1999] hap:// ehpnett.nies.nib.gov/docs/1999/107p93-97bffgeron/abstract.html A number of man-made compounds mimic estrogens, although with a lower potency than natural steroidal estrogens (1-3). When considered individually, these chemicals may exist in the environment in concentrations too low to be of concern. In combination, however, low dosages of these same compounds may act synergistically to produce a strong estrogenic response. This low-dose synergy was first shown with polychlorinated biphenyls (PCBs) using an in vivo sex-reversal assay in the red-eared slider turtle (Trachemys scripta) (4). Although the pesticides endosulfan and dieldrin were reported to produce similar synergy using a yeast gene expression system (5), subsequent studies failed to replicate this result (6,7). Thus, controversy still surrounds environmental estrogens and whether they exhibit synergistic activity. This is an especially important question because low dosages of PCBs and pesticides could pose a health risk through inappropriate activation of estrogen-regulated processes. Indeed, naturally occurring steroidal estrogens play a prominent role in early development and in adult reproductive function through their effects on cell differentiation and cellular organization of the ovary (8-10).The developmental effects of steroidal estrogens are even more pronounced in the red-eared slider turtle because sex steroids have been implicated in the process of temperature-dependent sex determination (11). Gonadal sex in this and many other reptiles is determined by embryonic incubation temperature. In this particular species, eggs incubated at constant temperatures below 28.60C develop as males, eggs incubated at or above 29.60C develop as females, and increasing temperature within the narrow 28.6-29.60C range produces increasing proportions of females (12). Moreover, temperature has its effect during a critical period of deve...

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Developmental synergism of steroidal estrogens in sex determination.

Bergeron

Willingham

Osborn

et al. 1999

Environ Health Perspect

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“…Indeed, oestradiol production just after hatching masculinizes the brain in young males so that as adults they can respond to the activational effect of testosterone and sing [41]. In the turtle Trachemys scripta, sex is determined by the temperature of the egg's incubation; administration of oestradiol to eggs at a temperature that normally produces only males can overcome the effects of temperature and produce females [42].…”

Section: Endocrine Influence On the Phenotype (A) Organizational And mentioning

confidence: 99%

Hormonally mediated maternal effects, individual strategy and global change

Meylan¹,

Miles

Clobert

2012

Phil. Trans. R. Soc. B

101

108

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A challenge to ecologists and evolutionary biologists is predicting organismal responses to the anticipated changes to global ecosystems through climate change. Most evidence suggests that short-term global change may involve increasing occurrences of extreme events, therefore the immediate response of individuals will be determined by physiological capacities and life-history adaptations to cope with extreme environmental conditions. Here, we consider the role of hormones and maternal effects in determining the persistence of species in altered environments. Hormones, specifically steroids, are critical for patterning the behaviour and morphology of parents and their offspring. Hence, steroids have a pervasive influence on multiple aspects of the offspring phenotype over its lifespan. Stress hormones, e.g. glucocorticoids, modulate and perturb phenotypes both early in development and later into adulthood. Females exposed to abiotic stressors during reproduction may alter the phenotypes by manipulation of hormones to the embryos. Thus, hormone-mediated maternal effects, which generate phenotypic plasticity, may be one avenue for coping with global change. Variation in exposure to hormones during development influences both the propensity to disperse, which alters metapopulation dynamics, and population dynamics, by affecting either recruitment to the population or subsequent life-history characteristics of the offspring. We suggest that hormones may be an informative index to the potential for populations to adapt to changing environments.

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Expression of P450_arom in Malaclemys terrapin and Chelydra serpentina: A tale of two sites

et al. 2001

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The formation of estrogens from androgens in all vertebrates is catalyzed by the "aromatase" complex, which consists of a membrane bound P(450) enzyme, P(450) aromatase (which binds the androgen substrate and inserts an oxygen into the molecule), and a flavoprotein (NADPH-cytochrome P450 reductase). Among vertebrates, the two major sites of aromatase expression are the brain and gonads. Given the importance of estrogen in reptile sex determination, we set out to examine whether P450arom was involved in the initiation and/or stabilization of sex determination in turtles. We examined the expression of aromatase activity in the brain and gonads of two turtle species exhibiting temperature dependent sex determination (TSD), the diamondback terrapin (Malaclemys terrapin), and the common snapping turtle (Chelydra serpentina). Estradiol when applied at stage 14 of the terrapin induces expression of aromatase in the gonad of embryos incubated at male temperatures (26.5 degrees C). The level of expression is similar to that of a normal embryonic ovary. When applied at stage 22, estradiol does not induce aromatase expression in the terrapin. The xenoestrogen, nonylphenol, sex reverses terrapin embryos at 26.5 degrees C. Letrazole, a nonsteroidal aromatase inhibitor, suppresses aromatase activity in the brain at either incubation temperature. Ovotestes are produced by letrazole administration in the terrapin when incubated at 30.5 degrees C. In the snapping turtle at stage 23, gonadal and brain aromatase activity in embryos incubated at female temperatures (30.5 degrees C) is nearly half that exhibited in terrapin embryos at the same temperature. Moreover, letrazole administration suppresses aromatase expression to nearly basal levels. At male incubation temperatures (26.5 degrees ), brain aromatase expression is nearly three times higher than at female temperatures, while gonadal expression levels are nearly one third lower. However, the gonadal expression levels at male temperatures in the snapping turtle are nearly 25 times higher than that found in the terrapin. Estradiol administration elevates this level nearly three fold. These data suggest that is not merely the expression of aromatase that is important for ovarian development, but that the level of expression may be more important.

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The Relative Effectiveness of Estrone, Estradiol-17β, and Estriol in Sex Reversal in the Red-Eared Slider (Trachemys scripta), a Turtle with Temperature-Dependent Sex Determination

Cited by 48 publications

References 6 publications

Developmental synergism of steroidal estrogens in sex determination.

Developmental synergism of steroidal estrogens in sex determination.

Hormonally mediated maternal effects, individual strategy and global change

Expression of P450_arom in Malaclemys terrapin and Chelydra serpentina: A tale of two sites

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The Relative Effectiveness of Estrone, Estradiol-17β, and Estriol in Sex Reversal in the Red-Eared Slider (Trachemys scripta), a Turtle with Temperature-Dependent Sex Determination

Cited by 48 publications

References 6 publications

Developmental synergism of steroidal estrogens in sex determination.

Developmental synergism of steroidal estrogens in sex determination.

Hormonally mediated maternal effects, individual strategy and global change

Expression of P450arom in Malaclemys terrapin and Chelydra serpentina: A tale of two sites

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Expression of P450_arom in Malaclemys terrapin and Chelydra serpentina: A tale of two sites