Meeting Abstract
African clawed frogs depend on sex-specific vocalizations to mediate reproduction. The male advertisement (fertility) call varies across species in sound pulse rate and in the complexity of its temporal structure. We examined the role of sex hormones in the vocal masculinization of two species of Xenopus, X. borealis and X. boumbaensis, which both exhibit evolutionarily derived and temporally simplified male advertisement call patterns, but display different degrees of vocal sex differences. In X. borealis, advertisement call simplification has occurred alongside reduced sex differences in call rapidity. In contrast, vocal sex differences are extreme in X. boumbaensis, as females do not produce calls. We previously showed that a loss of sex differences in vocal effector physiology has occurred in X. borealis, but not X. boumbaensis, suggesting species-specific modifications to the hormonal regulation of sexually differentiated features. Exogenous androgen treatment (but not ovariectomy alone) caused development of advertisement-like vocalizations in as quickly as one week (X. borealis) or 6 weeks (X. boumbaensis); advertisement inter-call intervals decreased over 16 weeks of treatment, but still remained elongated relative to intact male inter-call intervals. Additionally, androgen treatment caused significant increases in laryngeal mass, relative to that of controls. Our results suggest that androgen sensitivity of the vocal circuit is conserved across the Xenopus genus, and that androgens are capable of masculinizing vocal circuits even in cases of extreme vocal sex differences.
