Reproductive and thyroid hormone profiles in captive Western fence lizards (Sceloporus occidentalis) after a period of brumation

Abstract

Seasonal fluctuation in serum concentrations of sex steroid (testosterone [T] and 17beta-estradiol [E(2)]) and thyroid (triiodothyronine [T(3)] and thyroxine [T(4)]) hormones was determined in captive Western fence lizards (Sceloporus occidentalis). Samples were collected from male and female breeding pairs weekly for a 4-month period after their emergence from artificial brumation. Circulating levels of E(2) corresponded with the expected vitellogenic and ovulatory cycles in females, and surprisingly, E(2) in males followed a similar pattern, indicating a possible role in breeding behavior. Serum T was elevated in male lizards for the first 6 weeks after emergence from brumation, possibly related to an increase in the onset of active spermatogenesis. Thyroid hormones showed little cyclical activity throughout the breeding period, with the exception of small increases of T(3) at weeks 8 and 16, possibly implying an active role of this hormone with ovulation in females. Overall, these baseline hormone data are not only useful in developing this animal as a laboratory reptile model for assessment of endocrine-mediated toxicity, but also of value for understanding herpetological endocrinology and for application in the conservation of threatened species. Zoo Biol 27:36-48, 2008. (c) 2007 Wiley-Liss, Inc.

How do host sex and reproductive state affect host preference and feeding duration of ticks?

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The reproductive hormone cycle of adult female American alligators from a barrier island population

“…The sex steroids E 2 , P 4 , and testosterone, often show seasonal cyclicity and are highly studied regulators of reproduction in most vertebrates, playing key roles in the production and maturation of gametes (Jones & Swain 1996, Ott et al 2000, Edwards & Jones 2001, Brasfield et al 2008, Wack et al 2008, Smith et al 2010. In female alligators, as with nearly all oviparous vertebrates, E 2 triggers the hepatic production of vitellogenin (VTG), the primary precursor of egg yolk protein (Ho et al 1982, Ho 1987, Guillette et al 1997.…”

Noninvasive analysis of fecal reproductive hormone metabolites in female veiled chameleons (Chamaeleo calyptratus) by enzyme immunoassay

“…Advantages of noninvasive fecal steroid measurements include easy collection without the effects of stressful collection procedures, the possibility of unlimited repeated sampling and long‐term monitoring, and reduced effect of episodic fluctuations [Brasfield et al, 2008; Touma and Palme, 2005]. Fecal or urine hormone metabolite measurements reflect an integrated measure of steroid levels in the blood over a period of time and are useful for evaluating relative proportions and trends of excreted hormone metabolites [Goymann, 2005].…”