Anuran gender identification by fecal steroid analysis

Abstract

This study tested the hypothesis that steroid hormone metabolites can be measured in anuran feces and their concentrations used to identify the sex of adults. Fecal samples from American toads, Bufo americanus, and boreal toads, B. boreas boreas, were extracted using ethyl acetate, and the concentrations of estradiol, progesterone and testosterone metabolites were measured by enzyme immunoassays with antibodies commonly used to evaluate steroid hormone concentrations in mammalian species. In American toads, mean testosterone metabolite concentrations (Po0.05) between males (224.3715.5 ng/g feces) and females (80.7710.6 ng/g), but estradiol and progesterone metabolite concentrations did not. In contrast, estradiol immunoreactivity differed (Po0.05) between male (19.071.8 ng/g) and female (48.376.3 ng/g) boreal toads. Progesterone and testosterone metabolite concentrations did not differ. Fecal hormone metabolite analysis offers a promising noninvasive approach to gender identification in anuran amphibians. However, the group of metabolites differentiating gender may not be consistent among species.

Non-invasive reproductive and stress endocrinology in amphibian conservation physiology

“…For ex situ programmes, it enables predictions about, for example, why the species fail to breed in captivity, the success of an assisted breeding programme, the point when available resources for housing animals will become limiting, or the impact of the environment on an animal's physiology ( Carlstead et al , 1993 ). The non-invasive assessment of reproductive hormone metabolites in anuran faeces is supported by two recent publications ( Szymanski et al , 2006 ; Hogan et al , 2013 ). Earlier studies of amphibian hormones have focused on androgens, with testosterone or di-hydrotestosterone being described as the major plasma androgen measured in different amphibian species ( Kime and Hews, 1978 ; Canosa and Ceballos, 2002 ).…”

“…EC 90% success as the sexing hormone Germano et al (2012) EIA American toad ( Bufo americanus ) Captive Faecal EIA Sigma Chemical Company (St Louis, MO, USA) T, EC, P First report of faecal hormone metabolite analysis in amphibians. Szymanski et al (2006) Boreal toads ( Bufo boreas boreas ) T better sexing hormone than EC and P Abbreviations: ACTH, adrenocorticotrophic hormone; CORT, corticosterone; EC, estrone conjugate; EIA, enzyme immunoassay; P, progesterone; RIA, radio-immunoassay; and T, testosterone. …”

“…As there are many possible ways in which amphibians could process steroid hormones, it is difficult to predict the identities of specific metabolites they excrete, and one may anticipate species differences in the identity of the secreted hormone metabolites. Nevertheless, antibodies and EIA protocols that are well established in mammalian and bird species have been used for amphibians ( Munro and Stabenfeldt, 1984 ; Szymanski et al , 2006 ). To date, only three studies ( Germano et al , 2009 , 2012 ; Narayan et al , 2010b ) have demonstrated the patterns of reproductive hormone cycles in free-living populations of anurans using urinary-based testosterone, estrone conjugate and progesterone EIAs (see summary Table 1 ).…”

“…Recently, Germano et al (2012) established that urinary estrone conjugate had 94% success in identifying the sex of the IUCN endangered Maud Island frog ( Leiopelma pakeka ). Szymanski et al (2006) utilized non-invasive faecal hormone methods to distinguish sex in American toads ( B. americanus ) and boreal toads ( Bufo boreas boreas ). Their study reported that faecal testosterone metabolite concentrations provided the most useful measure of sex in the American toads (they found no overlap in the 95% confidence interval surrounding mean testosterone concentrations for males and females; Szymanski et al , 2006 ).…”

The many uses of non‐invasive faecal steroid monitoring in zoo and wildlife species

“…Baltic et al, 2005;Goymann, 2005;Möstl et al, 2005;Palme et al, 2005;Szoke et al, 2006) and, to a lesser extent, reptile (i.e. Atkins et al, 2002;Rittenhouse et al, 2005), amphibian (Szymanski et al, 2006) and fish (i.e. Turner et al, 2003;Ellis et al, 2004;Wysocki et al, 2006) species.…”