FINE STRUCTURE AND VITAL STAINING OF OSPHRADIUM OF THE SOUTHERN OYSTER DRILL, THAIS HAEMASTOMA CANALICULATA (GRAY) (PROSOBRANCHIA: MURICIDAE)

¹ Department of Zoology and Physiology, Louisiana State University, Baton Rouge, Louisiana 70803

The morphology of the osphradium of Thais haemastoma canaliculata (Gray) was examined using light microscopy, SEM, and TEM. The osphradium is composed of approximately 150-200 lamellae, each of which is divided into two distinct regions by a groove situated parallel to the dorsal edge of the organ. The dorsal one-fourth of each lamella is covered by dense cilia that are assumed to generate water currents about the osphradium. Ciliary tufts, located in small depressions, and numerous secretory cells are distributed uniformly on the ventral three-fourths of the lamellae. A thin tract of cilia borders the ventral edge of each lamella. The overall cellular organization is less complex than has been reported previously in other marine prosobranchs. Selective staining of putative chemoreceptors was performed using Procion Brilliant Yellow. Individual cells in the ventral region and the ventral edge of each lamella were Procion-positive. Results of this study suggest that ventral interlamellar regions and the ventral edge of each lamella are chemosensory regions, while the dorsal portion of each lamella is indifferent epithelium.