The early development and physiology of Xenopus laevis tadpole lateral line system

Abstract

Xenopus laevis has a lateral line mechanosensory system throughout its full life cycle. Previous studies of the tadpole lateral line system revealed that it may play a role in escape behaviour. In this study, we used DASPEI staining to reveal the location of tadpole lateral line neuromasts. Destroying these neuromasts with neomycin resulted in loss of escape responses in tadpoles. We then studied the physiology of anterior lateral line in immobilised tadpoles. Activating the neuromasts behind one eye could evoke asymmetrical motor nerve discharges when the tadpole was resting, suggestive of turning/escape, followed by fictive swimming. When the tadpole was already producing fictive swimming however, anterior lateral line activation reliably led to the termination of swimming. The anterior lateral line had spontaneous afferent discharges at rest, and when activated showed typical adaptation. There were also efferent activities during tadpole swimming, the activity of which was loosely in phase with ipsilateral motor nerve discharges, implying modulation by the motor circuit from the same side. Calcium imaging experiments located sensory interneurons in the primary anterior lateral line nucleus in the hindbrain. Future studies are needed to reveal how sensory information is processed by the central circuit to determine tadpole motor behaviour. Summary statementActivating tadpole anterior lateral line evokes escape responses followed by swimming and halts ongoing swimming. The afferent and efferent activities and sensory interneuron locations in the hindbrain are reported.