A Histological Study on the Visual Cell Layer of the Endemic Korean SpeciesLiobagrus mediadiposalis(Pisces: Amblycipitidae)

Water absorbs different amount of light by the depth of the water, which the deeper the depth is, the less light it absorbs. Also the optic properties of water also lead to different wavelengths of light such as long wavelengths (e.g., red, orange) being absorbed quickly or short one (blue, violet) being absorbed quite slowly (Engström, 1963; Marc & Sperling, 1976). In consideration of such water properties, fish vision is more important to feed on food items than other organs (an olfactory organ, a lateral line, and hairs on the jaw). Their retinas generally have both rod cells and cone cells (for scotopic and photopic vision). Activity patterns of teleost in general are divided largely into diurnal or nocturnal fish although there are overlapping periods of the time during the activity, which is closely related to their feeding habits to seek prey regardless of the kind of food items (Nag & Bhattacharjee, 1993, 2002). Furthermore, the feeding action is variable upon the size and shape, and setting of the eyes with its retinal structures by species, based on aquatic ecosystems on whether they inhabit deep or swallow waters, or bottom or surface waters, or when they are activated, the day or the night. Liobagrus mediadiposalis, a nocturnal and bottom-dwelling freshwater fish, is an endemic Korean catfish and preys on aquatic insects (Kim, 2013; Kim & Park, 2002). For the genus Liobagrus, except for ecological studies, the vision cells have been little known until now. Hence, this paper focused on studying the structure of the visual cells on the retina as part of understanding the relation between the vision and feeding habit surrounding its aquatic environment.