FINE-STRUCTURE OF THE PHOTOGENOUS AREAS IN THE BIOLUMINESCENT OPHIUROID AMPHIPHOLIS-SQUAMATA (ECHINODERMATA, OPHIURIDEA)

Amphipholis squamata is a small bioluminescent ophiuroid whose arms ar e the only body part to produce light. The morphology of the arms was described paying particular attention to the spinal ganglia, viz the a reas of most intense luminescence. Spinal ganglia consist of five diff erent cell types (A-E) which were studied at different stages of the p hotogenous reaction. Type D cells have numerous irregularlyshaped vacu oles, widespread Golgi apparatus and well-developed rough endoplasmic reticulum (RER) that show obvious ultrastructural changes after lumine scence. Type D cells appear, therefore, to be the best photocyte candi date. Type B and C cells were frequently observed in the nervous syste m outside spinal ganglia. Type A and E cells have not been described b efore. Type A cells are ciliated cells and type E cells extend long pr ocesses which are intimately associated with type D cells and epiderma l ciliated cells. Both type A and type E cells could take part to the stimulation pathway that triggers luminescence.