Crustaceans as Models to Investigate Memory Illustrated by Extensive Behavioral and Physiological Studies in Chasmagnathus

Abstract

In this and the following chapter we intend to illustrate the suitability of crustaceans for investigating the learning process through our own research with the crab Chasmagnathus. A visual danger stimulus elicits an escape response in the crab that declines after repeated presentations. When a long rest interval is interspersed between presentations (spaced training), an associative, long-lasting memory is formed, termed context-signal memory (CSM). When a short interval is interspersed (massed training), a non-associative, intermediate memory is formed, termed signal memory (SM). Such waning is retained as context-signal memory (CSM) or signal-memory (SM). The CSM, but not the SM, is cycloheximide-sensitive, mediated by the cAMP signal pathway, regulated by a muscarinic-cholinergic mechanism, and entails an increase in the Rel/NF-KB like-DNA-binding activity. A model standing for two putative memory mechanisms is discussed.