Ultrastructure of the optic gland of the squid Sepiotheutis sepioidea (Cephalopoda: Loliginidae)

I describe the fine structure of the optic gland (OG) in the tropical squid Sepiotheutis sepioidea at different sexual maturity stages. Squids were collected in Mochima National Park, Venezuela (10°; 20' 22 " - 10°; 24' N; 64° 19' - 64 ° 22' W). Morphometric characteristics and the development of reproductive organs at different sexual maturity stages (female n = 101; male n = 105), were significantly different (ANOVA, p < 0.001). The female gonadal index mean (GI = (ovary weight / body weight) x 100) between 0.1 - 2.95 %, and the male GI mean (GI = (testicule weight / body weight) x 100) oscillated between 0.22 - 1.38 %. The OG are a pair of oval organs located at the posterior edge of the optic tract of the cephalopod brain. The OG showed the same cellular types described in other cephalopods, with slight differences. The secretory cells in young individuals present a dendritic profile with thin cytoplasmic processes, numerous circular mitochondriae with tubular crests and abundant ribosomes. At the last stage of maturity the secretory cells contain rough endoplasmic reticulum in the form of dilated cisternae, with an active Golgi apparatus, secreting electron dense granules. Mitochondriae are scarce and lipofuchsin granules show an increase in size. Secretory cell nucleus length and organelle abundance showed oscillations associated with the life cycle.