title: Distinct lobes of Limulus ventral photoreceptors. I. Functional and anatomical properties of lobes revealed by removal of glial cells.
abstract: Removing the glial cells that encase Limulus ventral photoreceptors allows direct observation of the cell surface. Light microscopy of denuded photoreceptors reveals a subdivision of the cell body into lobes. Often one lobe, but sometimes several, is relatively clear and translucent (the R lobes). The lobe adjacent to the axon (the A lobe) has a textured appearance. Scanning electron microscopy shows that microvilli cover the surface of R lobes and are absent from the surface of A lobes. When a dim spot of light is incident on the R lobe, the probability of evoking a single photon response is two to three orders of magnitude higher than when the same spot is incident on the A lobe. We conclude that the sensitivity of the cell to light is principally a function of the R lobe.
mesh_terms: D000221:Adaptation, Ocular; D000818:Animals; D006737:Horseshoe Crabs / Q000033:anatomy & histology*; D008722:Methods; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000502:physiology / Q000648:ultrastructure*