Electrical coupling between fibre cells in amphibian and cephalopod lenses

The lenses of vertebrate and cephalopod eyes differ ontogenetically and in other respects. The vertebrate lens, derived from a single cell type, consists mainly of long fibre cells continuously produced by division and elongation of columnar epithelial cells near the lens equator. Almost 50% of the fibre cell surface consists of junctional complexes and the internal resistance, from point to point within the lens, is low compared with the surface membrane resistance. Thus the vertebrate lens is expected to behave as a well coupled syncytial system. The cephalopod lens, however, is formed by the fusion of two distinct cell types; the anterior segment has the same ontogenetic origin as the cornea but the posterior segment shares a common origin with the retina, and the plane of contact of the two cell types can be seen in light-microscope sections. Most of the lens is composed of long fibre cells similar in appearance to those found in the vertebrate lens, and membrane junctional regions between adjacent fibres have also been tentatively identified. We now describe electrophysiological investigations of cellular communications in the cephalopod lens, which show marked differences in the intercellular electrical coupling within the vertebrate (amphibian) and cephalopod lens.