Structure of cubozoan jellyfish eyes

The cubozoan jellyfish, Carybdea marsupialis, has four rhopalia, one on each quadrant of the bell. Each rhopalium contains one large eye; one small eye, and four ocelli. Both the large and small eyes have a cornea, lens, and retina of cilitated photoreceptors. Each photoreceptor contains a basally-located nucleus, medially-located pigment granules, and a ciliated apex filled with stacks of membrane. The base of each photoreceptor projects into a neural plexus while the apical end extends into a small space beneath the lens. Antisera that detect rhodopsin, and the green, red, blue, or ultraviolet opsin proteins in zebrafish were applied to the jellyfish eyes. Both the large and small eyes exhibited positive staining for rhodopsin, blue opsin, green opsin, and ultraviolet opsin. Rhodopsin, blue opsin, and green opsin staining were observed in the apical stacks of photoreceptor membranes, whereas UV opsin staining was observed in the mid to basal regions of some of the photoreceptors. Jellyfish eyes exposed to antibodies that recognize all photoreceptors, larval and adult, of Drosophila showed no staining.