scholarly journals Oil dispersant Corexit 9500 is weakly estrogenic, but does not skew the sex ratio in Alligator mississippiensis

2019 ◽  
Vol 40 (2) ◽  
pp. 245-256
Author(s):  
Nicole A. McNabb ◽  
Melissa C. Bernhard ◽  
Arnold Brunell ◽  
Russell H. Lowers ◽  
Yoshinao Katsu ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Alligator Mississippiensis ◽  
Oil Dispersant ◽  
Corexit 9500

Environmental regulation of sex determination in reptiles

1988 ◽  
Vol 322 (1208) ◽  
pp. 19-39 ◽  
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Growth And Development ◽  
Incubation Temperature ◽  
Sex Differentiation ◽  
Developmental Time ◽  
Alligator Mississippiensis ◽  
Phylogenetic Implications ◽  
History Of ◽  
Determining Factor

The various patterns of environmental sex determination in squamates, chelonians and crocodilians are described. High temperatures produce males in lizards and crocodiles but females in chelonians. Original experiments on the effects of incubation at 30 °C (100% females) or 33 °C (100% males) on development in Alligator mississippiensis are described. These include an investigation of the effect of exposing embryos briefly to a different incubation temperature on the sex ratio at hatching, and a study of the effects of 30 °C and 33 °C on growth and development of alligator embryos and gonads. A 7-day pulse of one temperature on the background of another was insufficient to alter the sex ratio dramatically. Incubation at 33 °C increased the rate of growth and development of alligator embryos. In particular, differentiation of the gonad at 33 °C was enhanced compared with 30 °C. A hypothesis is developed to explain the mechanism of temperature-dependent sex determination (TSD) in crocodilians. The processes of primary sex differentiation are considered to involve exposure to a dose of some male-determining factor during a specific quantum of developmental time during early incubation. The gene that encodes for the male- determining factor is considered to have an optimum temperature (33 °C). Any change in the temperature affects the expression o f this gene and affects the dose or quantum embryos are exposed to. In these cases there is production of females by default. The phylogenetic implications of TSD for crocodilians, and reptiles in particular, are related to the life history of the animal from conception to sexual maturity. Those animals that develop under optimal conditions grow fastest and largest and become male. A general association between the size of an animal and its sex is proposed for several types of vertebrate.

scholarly journals Can Xenobiotics Alter the Sex Ratio of Crocodilians in the Wild?

2021 ◽  
pp. 1-8
Author(s):  
Satomi Kohno
Keyword(s):  
Estrogen Receptor ◽  
Sex Ratio ◽  
Sex Determination ◽  
Ovarian Development ◽  
Alligator Mississippiensis ◽  
Control Group ◽  
Lake Apopka ◽  
In The Wild ◽  
The Impact ◽  
Estrogen Receptor 1

All crocodilians exhibit temperature-dependent sex determination without sex chromosomes. This temperature dependency can be overridden by exposure to estrogen via estrogen receptor 1. Thus, the sex ratio of crocodilian species is vulnerable to estrogenic xenobiotics. Multiple investigations of the mechanism and effects of xenobiotics in crocodilian species have been conducted since the early 1990s. This review focuses on the impact of xenobiotics on sex determination rather than gonadal functions in crocodilians. The thermosensitive and estrogen-sensitive periods that commit the bipotential gonad to develop as an ovary end by stages 24.5 and 25.3, respectively. In contrast, it is ambiguous when the estrogen-sensitive stage begins for ovarian development, although the thermosensitive period for ovarian development initiates around developmental stage 15 at an extreme female-producing temperature of 30°C. To accurately assess the effect of xenoestrogens on sex ratio in crocodilians, it is critical to collect eggs before the sex-determining period and to incubate them under precisely controlled temperatures. A well-studied system of xenobiotic effects on crocodilians is Lake Apopka (FL, USA), an EPA superfund clean-up site heavily contaminated with Dieldrin, Endrin, and <i>p,p&apos;</i>-DDE. The sum of estimated estrogenicity of xenobiotics measured in Lake Apopka was insufficient to activate the estrogen receptor 1 of <i>Alligator mississippiensis</i>, which is an essential receptor to induce ovarian development. Although juvenile <i>A. mississippiensis</i> showed gonadal alterations in sex hormone production and histology, the environmentally relevant concentration of xenobiotics in Lake Apopka was unlikely to alter the sex ratio of <i>A. mississippiensis.</i> Experimental exposure to xenobiotics such as 17α-ethynylestradiol, <i>p,p&apos;</i>-dichlorodiphenyldichloroethylene, and 2,3,7,8-tetrachlorodibenzodioxin at environmentally relevant concentrations in ovo induced more female offspring in <i>A. mississippiensis</i> as compared with the control group. Bisphenol-A, atrazine, 2,4-dichlorophenoxyacetic acid, endosulfan, and Corexit did not alter the sex ratio of <i>A. mississippiensis</i> or <i>Caiman latirostris</i> under the tested conditions. Egg-incubation temperature has pronounced effects on estrogen sensitivity in crocodilian sex determination. Therefore, crocodilians are vulnerable to xenobiotic contamination and climate change in the wild. It is vital to further investigate the detailed mechanism and effects of environmental xenobiotics in crocodilian sex determination to mitigate their effect on sex ratio and conserve this ancient lineage.

scholarly journals Spatial and temporal variation in nest temperatures forecasts sex ratio skews in a crocodilian with environmental sex determination

2020 ◽  
Vol 287 (1926) ◽  
pp. 20200210
Author(s):  
Samantha L. Bock ◽  
Russell H. Lowers ◽  
Thomas R. Rainwater ◽  
Eric Stolen ◽  
John M. Drake ◽  
...  
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Sex Determination ◽  
Temperature Variation ◽  
Climatic Factors ◽  
Sex Ratios ◽  
Alligator Mississippiensis ◽  
Spatial And Temporal Variation ◽  
Nest Temperature ◽  
Offspring Sex

Species displaying temperature-dependent sex determination (TSD) are especially vulnerable to the effects of a rapidly changing global climate due to their profound sensitivity to thermal cues during development. Predicting the consequences of climate change for these species, including skewed offspring sex ratios, depends on understanding how climatic factors interface with features of maternal nesting behaviour to shape the developmental environment. Here, we measure thermal profiles in 86 nests at two geographically distinct sites in the northern and southern regions of the American alligator's ( Alligator mississippiensis ) geographical range, and examine the influence of both climatic factors and maternally driven nest characteristics on nest temperature variation. Changes in daily maximum air temperatures drive annual trends in nest temperatures, while variation in individual nest temperatures is also related to local habitat factors and microclimate characteristics. Without any compensatory nesting behaviours, nest temperatures are projected to increase by 1.6–3.7°C by the year 2100, and these changes are predicted to have dramatic consequences for offspring sex ratios. Exact sex ratio outcomes vary widely depending on site and emission scenario as a function of the unique temperature-by-sex reaction norm exhibited by all crocodilians. By revealing the ecological drivers of nest temperature variation in the American alligator, this study provides important insights into the potential consequences of climate change for crocodilian species, many of which are already threatened by extinction.

Comparison of Acute Aquatic Effects of the Oil Dispersant Corexit 9500 with Those of Other Corexit Series Dispersants

1996 ◽  
Vol 35 (2) ◽  
pp. 183-189 ◽  
Author(s):  
Michael M. Singer ◽  
Saji George ◽  
Susan Jacobson ◽  
Ina Lee ◽  
Lisa L. Weetman ◽  
...  
Keyword(s):  
Oil Dispersant ◽  
Corexit 9500 ◽  
Aquatic Effects

Die unbehandelten Kranken: Ältere Männer mit Depression

2008 ◽  
Vol 27 (07) ◽  
pp. 617-619 ◽  
Author(s):  
M. Wittmann ◽  
E. Haen ◽  
H. Spießl ◽  
H. Hausner
Keyword(s):  
Sex Ratio ◽  
Epidemiologische Studien

ZusammenfassungZahlreiche epidemiologische Studien zeigen, dass sich das Geschlechterverhältnis der Prävalenz depressiver Erkrankungen ab der 6. Lebensdekade – also nach der weiblichen Menopause – wieder annähert. Wir haben untersucht, ob sich dieser epidemiologische Effekt auch in der stationären Versorgung abbildet. Unter Verwendung der AGATE-Stichtagsdaten der Jahre 2000 bis 2004, wurde der Zusammenhang zwischen Geschlecht und Alter bei stationär behandelten depressiven Patienten analysiert. Der Zusammenhang zwischen Geschlechterverhältnis und dem Alter wurde mithilfe des Korrelationskoeffizienten nach Spearman sowie mit χ2-Test untersucht. In der 5. und 6. Lebensdekade lag die Sex-Ratio F/M bei 1,7:1, sie stieg in der 7. Dekade auf 2,2:1 und in der 8. Dekade auf 2,6:1 an. Anders als aufgrund epidemiologischer Studien zu erwarten wäre, nähert sich in der stationär psychiatrischen Versorgung das Verhältnis depressiver Patienten im Alter nicht an. Depressive ältere Männer sind also im stationären Versorgungssystem unterrepräsentiert.

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