Determination of sex steroids in shed skin of the beaded lizard Heloderma suspectum ("Gila Monster")

Abstract

Measurement of steroid hormones in skin appendages such as mammalian hair or claws and in avian feathers represents a recognized non-invasive method for the determination of these parameters. The aim of this pilot study in the Gila Monster was to investigate whether the measurement of sex steroids in shed skin may be employed for the monitoring of endocrine gonadal function or sex determination in reptiles. Shed skins were available from 11 female and 7 male adult and sexually mature animals. Large pieces of skin were initially cut into smaller pieces with scissors. The resultant dermal fragments were finely ground under liquid nitrogen and finally extracted with organic solvents. The following parameters were determined radioimmunologically in the dried and re-dissolved extracts: progesterone (P4), estradiol-17β (E2), testosterone (T), free total estrogens (fGÖ) and free plus conjugated total estrogens (fkGÖ). For P4 (p = 0.0052) and E2 (p = 0.0079) significant sex differences were found with higher concentrations in females compared to males. Unexpectedly, the measured values for T were also significantly higher in females (p = 0.0232) than in males, with the concentrations overall only slightly above the detection limit. Compared to fGÖ, the concentrations of fkGÖ were only slightly higher, with no significant differences between both sexes. In this pilot study, the methods employed did not allow for reliable sex determination in individual animals, neither alone nor in combination, due to an overlap between the sexes. In principle, however, the measurement of sex steroids in shed skins could represent a useful method for non-invasive sex determination or endocrine gonadal function assessment in certain reptile species.