A FIELD STUDY OF CHEMOTACTIC RESPONSES OF THE MARINE MUD SNAIL, Nassarius obsoletus

Chemotactic responses of the salt marsh mud snail Nassarius obsoletus were tested in the field, to the introduction of a crushed conspecific and to the sympatric gastropod Littorina littorea and the bivalve Modiolus demissus. The snails responded with burial and escape to the conspecific stimulus, with strong attraction and feeding to M. demissus, and with attraction and feeding to L. littorea. In blank tests, the numbers of snails fluctuated only slightly during half-hour observation periods. An alarm substance appears to be liberated from wounded N. obsoletus which causes rapid disappearance of conspecific snails in an area of up to 50 cm radius.