Effects of temperature on escape jetting in the squid Loligo opalescens

In Loligo opalescens, a sudden visual stimulus (flash) elicits a stereotype d, short-latency escape response that is controlled primarily by the giant axon system at 15 degrees C, We used this startle response as an assay to e xamine the effects of acute temperature changes down to 6 degrees C on beha vioral and physiological aspects of escape jetting, In free-swimming squid, latency, distance traveled and peak velocity for single escape jets all in creased as temperature decreased. In restrained squid, intra-mantle pressur e transients during escape jets increased in latency, duration and amplitud e at low temperature. Recordings of stellar nerve activity revealed repetit ive firing of the giant motor axon accompanied by increased activity in the non-giant motor axons that run in parallel, Selective stimulation of giant and non-giant motor axons in isolated nerve-muscle preparations failed to show the effects seen in vivo, i.e. increased peak force and increased neur al activity at low temperature. Taken together, these results suggest that L. opalescens is able to compensate escape jetting performance for the effe cts of acute temperature reduction. A major portion of this compensation ap pears to occur in the central nervous system and involves alterations in th e recruitment pattern of both the giant and non-giant axon systems.