Sex steroids and vasotocin interact in a female amphibian (Taricha granulosa) to elicit female-like egg-laying behavior or male-like courtship

Abstract

Female egg-laying behaviors and male amplectic clasping behaviors in the rough-skinned newt (Taricha granulosa) are similar in that animals clasp an object. In the case of egg-laying, females clasp submerged inanimate objects, whereas in amplexus, males clasp conspecific females. Considering these behavioral similarities and differences, we investigated the possibility that gonadal steroids and vasotocin (AVT) interact to control egg-laying behaviors, as has been shown for the control of amplexus in Taricha males. Intact, gravid T. granulosa females injected ip with AVT, unlike those injected with saline, exhibited egg-laying behaviors and oviposition. In ovariectomy-steroid-implant studies, no saline-injected female exhibited egg-laying behaviors, whereas AVT-injected ovariectomized females exhibited egg-laying behaviors if implanted with estradiol (E2), testosterone, or dihydrotestosterone (DHT), and not if implanted with empty capsules. When given a choice between clasping aquatic vegetation or other females (amplectic clasping), following an AVT injection, unoperated and sham-operated control females and ovariectomized females with E2 implants did not preferentially clasp aquatic vegetation over other females. In contrast, AVT-injected ovariectomized females with DHT implants preferentially clasped other females. Thus, exposure of Taricha females to estrogens or androgens appears to determine whether the AVT-induced clasping is egg-laying or amplectic clasping.