196 NONINVASIVE HORMONE MEASUREMENTS FOR GENDER IDENTIFICATION IN MONOMORPHIC ANURANS

Abstract

Noninvasive techniques have been successful in distinguishing gender in dimorphic amphibian models (Szymanski DC et al. 2006 Zoo Biol. 25, 35-46). The aim of this study was to assess gender-specific fecal hormone metabolite concentrations in 2 dimorphic and 2 monomorphic, critically endangered species of amphibians to assist in ex situ breeding efforts. Fecal samples from 2 dimorphic anurans, the Puerto Rican Crested Toad (Bufo lemur) and the Wyoming Toad (Bufo baxteri) and 2 monomorphic species, the Mountain Chicken Frog (Leptodactylus fallax) and the Dusky Gopher Frog (Lithobates sevosa) were measured by enzyme immunoassay for sex-specific hormone differences (Student’s t-test; P < 0.05) among 6 variables (concentrations of estradiol (E2), progesterone (P), and testosterone (T), and ratios of P:E2, T:E2, and P:T). Values are presented as means ± SEM. Mountain Chicken Frog samples were obtained from individuals of known sex. Dusky Gopher Frog samples were from confirmed females but males were presumed based on subtle physical characteristics. The E2 concentrations (ng g-1) were significantly higher in females than males (P < 0.05) in all species except for the Dusky Gopher Frog. However, males in all 4 species, including the presumptive Dusky Gopher Frog males, exhibited significantly higher P:E2 and T:E2 ratios than females. Additionally, Wyoming Toad and Mountain Chicken Frog females had significantly higher P:T ratios than males (0.19 ± 0.05 v. 0.06 ± 0.00 and 0.34 ± 0.03 v. 0.20 ± 0.02, respectively). Similar to the American Toad (Szymanski et al. 2006), presumptive Dusky Gopher Frog males measured significantly higher T concentrations compared with females (376.4 ± 118.5 ng g-1 v. 174.0 ± 23.1 ngg-1, respectively). Although species-specific differences are apparent, fecal hormone measurements can be used to identify sex in monomorphic species and offer a potential tool for the captive breeding of endangered anurans. Table 1.