INTERACTIONS OF SENSORY SYSTEMS AND ORIENTATION BEHAVIOUR IN LYMNAEA STAGNALIS (L.)

SUMMARY Many invertebrates display under experimental conditions fixed orientation behaviour relative to particular stimuli. This indicates that the underlying neural mechanism is relatively simple. Despite this property animals in the field often can turn orientation relative to a particular stimulus on or off or they can change the sign of orientation. From the literature it appeared that in a number of cases these changes in orientation are related to external or internal conditions of the animal. Moreover, the way in which these changes take place indicate that the neural mechanism involved is of the same complexity as that which induces orientation behaviour. The present study deals with changes in orientation behaviour in gastropods. Special attention is paid to orientation behaviour of the fresh water snail Lymnaea stagnalis . A number of conditions under which changes in gravitational orientation take place are described with special reference to the sensory systems involved. The biological significance of these changes in orientation and the possible role of interactions of sensory systems in the induction of changes in orientation behaviour are discussed.