Coordinated Beating of Gill Lateral Cell Cilia of Mytilus edulis and Crassostrea virginica Involves Neuronal Innervation and Functioning Gap Junctions
Authors: Buchanan Reneice , Robertson Cheyanne , Frank Dane , Catapane Edward J , Carroll Margaret A 
Published: November 2023

Suspension feeding bivalves use a ciliary pump driven by lateral cilia on gill filaments to provide water currents for feeding, respiration and waste elimination. These cells in Mytilus edulis and Crassostrea virginica are innervated by serotonin and dopamine nerves. Serotonin increases beating rates and dopamine decreases it. The cellular mechanism regulating lateral cell cilia beating is not fully explained. Gill filaments receive branches from the branchial nerve, but it is unclear if each cell is individually innervated. Gill lateral cells have gap junctions and questions arise if gap junctions are involved in coordinating beating. Previously we found gap junctions between gill lateral cells in C. virginica and the gap junctions are involved in coordinating lateral cell cilia beating rates from cell to cell. We hypothesize gap junctions are present and involved in coordinating lateral cell to lateral cell cilia beating in M. edulis. To study this we used immunohistofluorescence with anti‐gap junction 1° antibodies (anti‐Pannexin‐1) and FITC labeled 2° antibodies and found gap junctions present. To determine if gap junctions are involved in coordinating lateral cell cilia beating from cell to cell we set up M. edulis gill preparation, similar to our previous study with C. virginica, in which gill filaments were divided into proximal and distal sections by a petroleum jelly barrier that prevented diffusion of drugs from side to side. We stimulated the branchial nerve entering the proximal end of the filaments with suction electrodes (5 hz, 2 msec, 2 volts). Stroboscopic microscopy was used to measure cilia beating rates. Drugs were applied to distal ends of preparations and beating rates of proximal and distal ends were compared. Lindane caused a dose‐dependent (10−7 – 10−4M) blockage of beating. Lindane is reported to reduce gap junction permeability and increase intracellular Ca2+, so we used the Ca2+ channel blocker diltiazem with lindane and found diltiazem (10−4M) alone did not alter beating rates, nor did it alter the actions of lindane. We also observed and videotaped in both M. edulis and C. virginica that clusters of connected lateral cells on the same gill filaments have cilia that beat at coordinated rates without lindane, but at discoordinated rates in the presence of 10−5M lindane. This suggests, that like cardiac tissue, there are pacemaker cells and follower cells in gill filaments. The results show the physiological functioning of gap junctions involved in coordinating gill lateral cell cilia beating in two bivalve species and neuronal innervation to filaments in conjunction with functioning gap junctions are necessary to coordinate beating rates in both bivalves. Disrupting either one interferes with the normal response.

Support or Funding Information

This work was supported by grants 690340047 of PSC‐CUNY, 2R25GM06003 of the Bridge Program of NIGMS and a Carnegie Foundation award.