General and histological structures of different parts of eye in Beaked Sea Snake, Enhydrina schistosa (Daudin 1803)

Study of eye structure in Enhydrina schistosa is an important subject and yet not enough as it is an active hunter that lives in shallow waters and some active predators like sea eagles and sharks are feeding at it. In this study Scanning Electron Microscope (SEM) was used for observing cellular layers in details. Specimens were collected from water surface in Chabahar Bay. The eyes were fixed in Bouin’s fluid and 10% formalin. There is a transparent layer (Spectacle) in front of the cornea (with protective role) with a three-layered structure. The sclera and cornea are quite thick with protective role against water pressure and mechanical stresses. The choroid consists of a loose tissue. The retina is composed of only a few cones and rods are absent that is evidence of the low visual capability in this successful marine reptile. Cone cells density in Ventral (V) and Dorsal (D) quadrants is higher than Temporal (T) and Nasal (N) quadrants and also Cone cells density in Ventral quadrant is higher than Dorsal quadrant. It seems Ventral quadrant (with highest cone cells density) might have a role in detecting aerial predators (sea eagles) and Dorsal quadrant (with lower cone cells density than Ventral quadrant) might have been engaged (not so important) in feeding on demersal fishes.