A light and electron microscopic study of the pineal in the blind goby, Typhlogobius californiensis (Pisces: Gobiidae).

The pineal of the burrow-inhabiting, blind goby, Typhlogobius californiensis, was studied by light and electron microscopy. The two predominant cell types were photoreceptor and supportive cells. Ganglion cells could not be positively identified. The majority of photoreceptor cells had well developed outer segments and made apparent synaptic contact with nerve processes of unknown origin. Similar unmyelinated nerve fibers containing dense-cored vesicles were seen descending the pineal stalk. The cytoplasm of supportive cells contained several Golgi zones, occasional dense aggregations of smooth endoplasmic reticulum, abundant quantities of glycogen, some dense-cored vesicles and unusual rod crystalline inclusions measuring approximately 0.5 micrometer in width and 4-5 micrometer in length. These observations suggest that the pineal in this light-deprived species has retained its photoreceptive function and is a metabolically active organ which may also function in secretion.