Freeze-Fracture and Histofluorescence Studies on Photoreceptive Membranes of Medusan Ocelli(Physiology)

概要

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Intramembranous particles (IMPs) in various membranous components of medusan ocelli were studied using four different types in basic organisation ; flat (Aurelia aurita), cupulate with everted (Spirocodon saltatrix) and inverted (A. aurita) sensory cells and lens-bearing (Charybdea rastonii). In addition, a histofluorescence technique specific for retinal-based proteins was applied to thelenseye. Apart from the flat ocellus of A. aurita, average diameters and densities of IMPs on the P-faces of the microvillar and ciliary membranes of the sensory cells in the other three types ranged 8-9 nm and 5,000-6,000/μm^2, respectively, and the densities were significantly higher than those in non-photoreceptive constituents of the ocelli. In the flat ocellus of A. aurita, P-face particles in the microvillar and the ciliary membranes were much less in densities and larger in diameters. In the lens eye of C. rastonii, the specific fluorescence was restricted to the ocular cavity where putative sensory microvilli were densely packed. From these results, we suggest that with the exception for the flat ocellus of A. aurita, the microvilli and the cilia in the three types of ocelli are in fact involved in primary photoreception.