FRANK, D.M.; DEATON, L.E.*; WARD, J.E.; SHUMWAY, S.E.; University of Connecticut, Groton; University of Louisiana at Lafayette; University of Connecticut, Groton; University of Connecticut, Groton: Gill cilia in the blue mussel, Mytilus edulis: Effects of neurotransmitters and calcium blockers

It is generally accepted that the lateral cilia of the gills of bivalve molluscs are inhibited by dopaminergic and excited by serotonergic innervation. These conclusions are based, in part, on experiments with excised gills of the mussel, Mytilus edulis. We examined the effects of serotonin (5HT), dopamine (DA), apomorphine (APO) and lanthanum on the pumping activity of intact M. edulis and the ciliary activity of isolated gill tissue. We also exposed isolated gill filaments to the calcium channel blockers cobalt chloride and verapamil. Whole animals and freshly excised gill pieces were kept in filtered seawater at ambient temperature. Drugs were added directly to the bath water. The activity of the lateral cilia of isolated gills was monitored with an inverted compound microscope. The pumping velocity of whole animals was measured by particle image velocimetry. Lanthanum induced extensive shedding of gill epithelial cells in isolated tissues and in whole animals; effects on the lateral cilia could not be observed. DA, cobalt chloride and verapamil had no effect on the lateral cilia of isolated gill sections. APO (1x10-6 M) partially inhibited the lateral cilia of 30% of isolated gills; 50% were inhibited by 1x10-5 M APO. APO (1x10-6 M) had a significant negative effect on the pumping velocities of intact mussels. 5HT appeared to increase synchrony (metachronism) of the lateral cilia in isolated gills.