Eye structure of Ophryotrocha puerilis (Polychaeta: Dorvilleidae).

The protandric hermaphrodite Ophryotrocha puerilis possesses one pair of eyes. They are located in the peristomium. Each light-sensitive organ consists of one sensory cell and one to two supporting cell(s) embedded in a cup-shaped reflector. The sensory-supporting cell complex is enveloped by a basal lamina. This lamina is supposed to be identical with the neural lamella. Thus the eyes proper have to be regarded as protrusions from the brain, while epidermal cells seem to differentiate to crystalline cells (reflector) and are deposited onto the sensory complex. The reflector is built up by several cup-shaped cells (juveniles, 4-5; adults, 10-12). Each of these cells comprises a multilayer of parallel-oriented, membrane-bound crystalline platelets which are thought to be guanine. The sensory cell is of the inverted rhabdomere type. Submicrovillar cisternae, typical for most polychaete eyes, are lacking. The first and always present supporting cell entirely envelops the sensory cell, thus forming the extracellular space around the rhabdomere. It does not contain any pigment granules. Often but not always a second supporting cell has been observed surrounding the sensory cell and first supporting cell. It is interpreted as a glial cell. In the sensory cell beneath the rhabdomere, pino- and phagocytosis can be observed and secondary lysosomes are found in high densities. Preliminary results seem to demonstrate that there is no distinct diurnal cycle of receptoral membrane recycling. In comparison with the ocelli of Dinophilidae, which have been interpreted as a dorvilleid-related family, morphological differences and their application to phylogenetic considerations are discussed.