Plasma steroid concentrations in relation to size and age in juvenile alligators from two Florida lakes

Department of Zoology, 223 Bartram Hall, University of Florida, Gainesville, FL 32611-8525, USA.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology (Impact Factor: 1.97). 05/2002; 131(4):923-30. DOI: 10.1016/S1095-6433(02)00025-9
Source: PubMed


Previous studies have reported a number of physiological differences among juvenile alligators from two well-studied populations (Lake Apopka and Lake Woodruff) in north central Florida. These studies obtained alligators of similar size from each lake under the assumption that the animals were of similar age. Lake Apopka is a hypertrophic lake with a 50-year history of contamination from agricultural and municipal operations, whereas Lake Woodruff is a eutrophic lake and part of a National Wildlife Refuge that receives little point source pollution. If growth rates differ among these areas, it could be argued that differences in endocrine parameters reported previously (e.g. steroid or thyroid hormone concentrations) could be the result of differences in the animals' ages. Using growth annuli in cross-sections of femurs, we estimated the ages of juvenile alligators and compared the relationship of estradiol-17beta (E(2)) and testosterone (T) to size and age within each lake and sex. No differences were detected in the relationship between size and age between the two areas indicating similar growth rates between lakes. Plasma E(2) was positively related to size in females from Lake Apopka, and age in Woodruff females. Males from Lake Apopka had elevated plasma E(2) compared with Lake Woodruff males and did not differ from Woodruff females. No significant relationships were detected for T from either lake, and no differences in plasma T were detected among lakes or sexes. Our data indicate that both size and age can have a significant relationship with steroid concentrations. However, the relationship between steroid concentrations and size or age differed between lakes. We suggest both factors should be considered when conducting physiological studies where there is evidence to suggest growth rates may differ among populations.

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Available from: Louis J Guillette, Jul 23, 2014
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    • "TSD can be experimentally altered by way of the administration of select exogenous compounds. A number of studies have shown that treatment of embryonated eggs with exogenous estradiol induces feminization at male temperatures, whereas treatment with aromatase (enzyme converting androgens into estrogens) inhibitors at female temperatures prevents normal ovarian development (Bull et al. 1988; Crain et al. 1997; Gabriel et al. 2001; Lance and Bogart 1994; Milnes et al. 2002). Exogenous estrogen exposure may also impair normal development. "
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    Archives of Environmental Contamination and Toxicology 11/2013; 65(4):704-714. DOI:10.1007/s00244-013-9953-x · 1.90 Impact Factor
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    • "A recent work that also acknowledges this physiological cyclicity states that future studies of endocrine disruption in ectotherms should consider size-specific responses to endocrine-disrupting chemicals (Crain et al. 1998). It also has previously been reported that alligators and crocodiles of varying sizes may manifest differences in terms of their steroid concentrations (Milnes et al. 2002; Rainwater 2003). Because differences in lifestyle may result in differences in exposure risk in these long-lived animals, in this study we investigated concentrations of OCPs and PCBs bioaccumulated by wild and farm female and male Morelet's crocodiles. "
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    ABSTRACT: Effects of endocrine disruptors on reproductive variables of top predators, such as alligators and crocodiles, have long been cited. Due to their long life span, these predators provide us with historic contaminant annals. In this study we tried to test whether lifestyle (free-ranging vs. farm animals) and reproductive age of Morelet's crocodiles in Campeche, Mexico, affect the bioaccumulation of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Subsequently, we tested to see whether their concentration was related to steroid hormones (testosterone and estradiol-17β) levels once normal cyclic hormone variation and reproductive age had been taken into account. From the group of contaminants considered (analyzed as families), only frequency of hexachlorocyclohexanes (∑HCH) and ∑PCB permitted analyses. Whereas there was a greater concentration of ∑HCH bioaccumulated by free-ranging crocodiles, ∑PCB was found in equal quantities in free-ranging and farm animals. No difference was observed in relation to reproductive age for any of the contaminants. However, ∑PCB concentrations were related to testosterone levels among female crocodiles. This androgenic effect of ∑PCB has not been reported previously. Because testosterone promotes aggressive behavior in vertebrates, excessive aggression during the estrous season, or when female crocodiles should be caring for their young, could result in reproductive failure in Morelet's crocodiles and potential long-term decline of the population.
    Archives of Environmental Contamination and Toxicology 10/2011; 62(3):445-54. DOI:10.1007/s00244-011-9716-5 · 1.90 Impact Factor
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    • "For example, red-eared slider turtles exposed experimentally to pesticides or their metabolites display altered sex ratios at hatching, and the males were demasculinized as demonstrated by an increased estrogen/androgen ratio of testicular hormone synthesis (Willingham et al., 2000). A similar pattern has been described in American alligators experimentally exposed to various estrogens or pesticides (or their metabolites) (Crain et al., 1997; Matter et al., 1998; Milnes et al., 2002; Rooney and Guillette, 2000) or naturally (Guillette et al., 2000, 1994). In addition to altered gonadal steroidogenesis, male alligators from lakes contaminated with EDCs display smaller, abnormally developed phalli (Guillette et al., 1996; 1999b). "
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