Conspecific injury fluids induce an electrophysiological response in the clonal tunicate Clavelina huntsmani

Abstract

Electrophysiological activity in the branchial basket of the clonal tunicate Clavelina huntsmani was monitored while exposing study specimens to injury fluids of conspecifics. Extracellular suction electrode recordings were used. Ciliary arrest potentials, generated by simultaneous arrest of stigmatal cilia across the branchial basket, were consistently precipitated within 3 min of exposure to conspecific injury fluids. Control fluid cues, including boiled fluid from injured conspecifics, did not provoke a similar response. This suggests that a heat-labile compound—potentially an alarm pheromone—is involved. The species-specific nature of the response constitutes the first evidence produced for alarm signaling in ascidians. This may serve to advance our understanding of both predator–prey interactions in sessile, clonal marine invertebrates and the possible ecological relevance of some of the diverse bioactive metabolites produced by ascidians.