Associative learning in the starfish Marthasterias glacialis, a simple model for the study of learning

Abstract

Appetitive phase of the feeding response in the starfish Marthasterias glacialis can be triggered by chemical stimuli emanating from a cotton food model. The surface of the food model is a stimulus releasing the consumatory phase of the feeding behaviour. If mild electrick shocks are delivered 6 seconds after the tube feet touch the cotton an escape response follows. In few repeated trials avoidance response which is equal to escape response appears and the shocks are ommited. Later the animals either avoid the food models or enter the consumatory phase of the feeding response. The situation can be described in terms of approach-avoidance conflict. Two types of connections should be available in the central nervous system of the starfish: the first structures should enable the consumatory feeding response and the second structures the steretyped avoidance response. The “central filters” can act as a flip-flop with feeding and avoidance stable states. The conflict is after many trials resolved with a cessation of activity.