Behavioral analysis of lateral line and vestibular hair cell function in developing Xenopus laevis

Abstract

Xenopus tadpoles are aquatic, nocturnal animals with well-developed superficial lateral line neuromasts. We previously showed that these animals, from premetamorphic through early froglet stages, exhibit stereotyped responses to low velocity flow fields—they move downstream at flow onset, and then turn and orient towards the flow source (positive rheotaxis). They continue to station hold in this oriented position for the duration of the stimulus. Positive rheotaxis and station holding are disrupted, but not totally eliminated, when animals are exposed to high concentrations of the ototoxic drug gentamicin. These data suggest that another sensory system is involved in detection of current flow. To determine the role of vestibular hair cells in these behaviors, we injected gentamicin directly into the tadpoles' otic capsules. This procedure damaged the developing otoliths and resulted in abnormal circular swimming movements and increased latency of rheotaxis and station holding. These behaviors were not, however, completely disrupted. These data suggest that the lateral line and vestibular systems act together in mediating responses of Xenopus tadpoles to flow fields.