THE HYPOBRANCHIAL GLAND OF THE ESTUARINE SNAIL STRAMONITA-HAEMASTOMA-CANALICULATA (GRAY) (PROSOBRANCHIA, MURICIDAE) - A LIGHT AND ELECTRON-MICROSCOPIC STUDY

The general structure and secretory features of the hypobranchial glan d of Stramonita haemastoma canaliculata (Gray, 1839) were investigated using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The gland is composed of three distinct regions and occupies the right medial and lateral portions o f the dorsal mantle tissue. The ctenidia, osphradium, and rectum occup y the remainder of the mantle cavity. Eight distinct cell types were i dentified by LM. SEM and TEM analysis revealed active secretory cells in the two lateral areas (regions I and III). The ventral surface of t hese regions is ciliated and possesses pores through which the secreto ry product is released into the mantle cavity. Region II apparently fu nctions as a temporary storage area where secretory products accumulat e prior to their release from the snail. One of the secretory products of the hypobranchial gland possesses the staining characteristics of the 'Tyrian Purple'' dye. Its functional role in the feeding process o f the snail, if any, is presently unknown.