Ca²⁺-dependent arrest of cilia without uncoupling epithelial cells

Abstract

IN CERTAIN ciliated epithelia, for example, mussel gill lateral cell epithelium, metachronally coordinated ciliary beat can be arrested systematically, either after nervous¹ or local stimulation, for example by laser microinjury^2,3. In the latter case, the velocity of spread of arrest, its extent and decremental character suggest that the response depends on electrotonic coupling of the gill cells³. The lateral cells are coupled by extensive septate junctions and small gap junctions⁴, more basally located, which may act in a manner homologous to electrical synapses of nerve and muscle cells^5–7. Although intracellular microelectrode recordings of lateral cell depolarisation accompanying arrest after branchial nerve stimulation have been made in Mytilus¹, there are no reports of microelectrode studies of cell coupling in gill cells. We have used experimentally-induced spreading arrest to monitor the state of coupling in the lateral cell epithelium of a freshwater mussel (for example, Elliptio complanatus).