Neuronal Basis of Hunting and Feeding Behaviour in the Pteropod Mollusc Clione Limacina

Abstract

The pteropod mollusc Clione limacina is a predator, feeding on another pteropod mollusc, Limacina helicina. Essential elements of Clione's hunting and feeding behaviour can be evoked pharmacologically. The sensory input driven by the presence of Limacina is mimicked by physostigmine (PhS), the acetylcholinesterase inhibitor. Injection of PhS into Clione brought it to the state of hunting excitation accompanied by a reversal of the reaction to head stimulation. As a result, head stimulation, instead of a defence reaction, evoked active hunting behaviour. The 'fictive hunting behaviour', that is activation of main motor systems participating in hunting behaviour, could be evoked in a preparation of the isolated central nervous system (CNS) by PhS application. To some extent, activation of the motor systems was realized through serotonergic mechanisms. GABAergic mechanisms also play an important role in the organization of Clione's feeding behaviour. GABA application to the preparation of the isolated CNS resulted in activation of the feeding rhythm generator and excitation of the motoneurons supplying the protractor tentacle muscles. The results show that in gastropod molluscs complex behaviour involving different functional systems may be described in terms of the activity of single identified neurons.