Localization of actin filaments and microtubules in the cells of the Limulus lateral and ventral eyes.

The ommatidia of the lateral eye of the horseshoe crab, Limulus polyphemus, undergo rhythmic changes in structure that are driven by diurnal lighting and efferent neural activity from a circadian clock in the brain. This study uses cytochemical probes to investigate the cytoskeletal elements mediating these responses and to develop models for their control. Antibodies to actin and phallodin, a specific F-actin probe, label the rhabdom of lateral eye ommatidia, the cone cells of the ommatidial aperture, the ommatidial sheath, and the peripheral regions of the photoreceptor (retinular cell) cytoplasm. These probes also label the rhabdomere of ventral photoreceptors. Antibodies to tubulin label the eccentric cell dendrite and soma in each lateral eye ommatidium, the cone cells of the aperture, and the peripheral retinular cell cytoplasm. Models are proposed for the cytoskeletal mechanisms involved in controlling aperture and rhabdom shape, pigment movement, and shedding of rhabdomeral membrane.