Circuits underlying motor patterns of closely related species provide an ideal framework in which to study how evolution shapes behavioral variation. Male African clawed frogs (Xenopus and Silurana) advertisement call to attract female mates and silence male rivals. Males of each species produce a unique vocal pattern that serves as a species-identifier. Xenopus laevis is the most well-studied species in terms of its vocal behavior and underlying anatomy and physiology. The clade that includes X. laevis, or X. laevis senso lato, also includes 3 other species that diverged ~8.5 million years ago. All 4 of these species produce advertisement calls that include fast trills – trains of fast rate (~60 Hz) sound pulses. However, their calls differ substantially between species in measures of trill duration and period. I examined the premotor circuit underlying vocal patterning in three of these species: X. laevis, X. petersii, and X. victorianus. I used extracellular recordings to find that a premotor nucleus, DTAM, which is part of the vocal central pattern generator, is the likely source of species-variation of vocal patterns. Species-specific trill duration and period are intrinsic to the region of the hindbrain that includes DTAM. Next, I used blind whole-cell patch recordings in DTAM of X. laevis and X. petersii to examine the cells that encode trill duration and period. I identified homologous populations of premotor vocal cells in both species that code for trill duration and period in a species-specific manner. Together, these results support an autonomous role of the DTAM circuit for generation of species variation in call duration and period.

The vertebrate planar cell polarity (PCP) pathway has been previously found to control polarized cell behaviors rather than cell fate. We report here that disruption of Xenopus laevis orthologs of the Drosophila melanogaster PCP genes Xint or Xfy affected not only PCP-dependent convergent extension but also caused embryonic phenotypes consistent with defective Hedgehog signaling. These defects in Hedgehog signaling resulted from a broad requirement for Inturned and Fuzzy in ciliogenesis. We show that these proteins are necessary for the formation of both primary cilium in the neural tube and multi-cilia in the epidermis. Also, using Xenopus muco-ciliary epidermis, we demonstrated that one of the core PCP genes Dishevelled performs dual functions in ciliogenesis, basal body docking and planar polarization of ciliary beating. To this end, we showed that Dishevelled works in concert with the PCP effector protein Inturned and Rho GTPase to mediate the docking of basal bodies to the apical cell surface. We suggest that this docking involves a Dvl-dependent association of basal bodies with vesicles, and with the vesicle-trafficking protein Sec8. Finally, we showed that independent of their roles in apical docking, Dvl/PCP signaling is required again for directional ciliary beating. For the first time, this study uncovered the mechanism for controlling the apical docking of basal bodies. Moreover, the results suggest that the same Dvl/PCP signaling is also important for the planar polarization of ciliary beating in a vertebrate muco-ciliary epithelium. / text