Cholinergic and peptidergic regulation of siphon/mantle function in the zebra mussel, Dreissena polymorpha

Neurotransmitter regulation of the siphon and adjacent mantle region of bivalves has not previously been examined. In the biofouling bivalve, Dreissena polymorpha, acetylcholine and FMRFamide both elicited contractions of siphon/mantle preparations. Hexamethonium bromide inhibited acetylcholine-elicited contractions but had no effect on FMRFamide-elicited contractions. FMRFamide-like immunoreactivity and chromatographic evidence for acetylcholine were found in central ganglia and the siphon/mantle region. Extracts of siphons, gonads, and gills, separated on Sephadex G-25, also contained macromolecules larger than acetylcholine and FMRFamide that caused siphon/mantle contraction. These results demonstrate regulation of contraction by several potential neurotransmitter agents in a new bivalve preparation, the siphon/mantle.