Meeting Abstract

P2.4  Monday, Jan. 5   The evolution of neuromuscular systems for vocal behavior in the African clawed frog (Xenopus) LEININGER, E.C.**; KITAYAMA, K.; KELLEY, D.B.; Columbia University, New York , NY; Columbia University, New York , NY; Columbia University, New York , NY ecl2107@columbia.edu

African clawed frogs (Xenopus) vocalize to attract females and mediate male/male antagonistic interactions. Individual frogs rely on the temporal characteristics of calls to distinguish sex and reproductive state; these characteristics (particularly click rate) are also species-specific. To explore the origins of species differences in vocal signaling, we examined physiological properties of muscles in the vocal organ of X. borealis (a species with a slow, simple advertisement call) relative to X. laevis (a species with a fast, biphasic advertisement call). In X. laevis, female calls are slow and monotonous relative to male calls, and laryngeal muscle is sexually differentiated with respect to contractile speed, fiber number, fiber twitch type, and fiber recruitment. In X. borealis, a species where female calls can be as rapid as those of males, we report that while larynx weight and laryngeal muscle fiber size is sexually dimorphic, other characteristics such as fiber type, fiber recruitment, and the rates at which discrete tension transients can be produced do not differ between the sexes. This reduced sexual dimorphism is consistent with the greater overlap in click rate of calls from male and female X. borealis, compared to X. laevis. One mechanism that may contribute to reduced sexual dimorphism in X. borealis is reduced sensitivity to the masculinizing effects of androgen.