Research Journal of Animal, Veterinary and Fishery Sciences __ _____________ ______ ____ _ _ ISSN 2320 – 6 535 Vol. 1 ( 2 ), 1 - 4 , March (201 3 ) Res. J. Animal, Veterinary and Fishery Sci. International Science Congress Association 1 The Adaptive Modifications of Snout epidermis of a hill - stream Fish Schizothorax richardsonii of Kumaun Himalaya: A SEM Investigation Singh Hoshiyar 1* , Joshi S.C. 2 , Bisht Ila 1 and Agarwal S.K. 1 1 Department of Zoology, S.S.J. Campus Almora, Kumaun Universi ty Nainital, 263601, INDIA 2 Department of Zoology, Surajmal Agarwal Girls, P.G. College Kichha, K.U. Nainital, 263145, INDIA Available online at: www.isca.in Received 25 th January 201 3 , revised 7 th February 201 3 , accepted 21 st February 201 3 Abstract Surface architecture of snout epidermis of hill - stream fish, Schizothorax richardsonii (Gray) was examined by scanning electron microscopy, in an attempt to understand the structural and functional modifications in epitheli a, in relation to life in torrential streams. Mucous pores (opening of mucous cells) and epithelial cells were visualized to have developed a dense network of irregularly interwoven microridges which could be interpreted as a means to retain maximum possib le mucus at the surface of the epithelial cells in S. richardsonii in order to protect against physical abrasions. Snout epidermis is subjected to more frictional stress if compared with the epidermis covering the general body surface as it is first to com e in contact with water current, especially when fish swims upstream and hence correlation has been made in relation to friction. Keywords: SEM, s nout epidermis, hill - stream, surface. Introduction The snow trout Schizothorax richardsonii is the princip al indigenous fish of the Himalayas available in various upland resources. Snow trout S. richardsonii is the most important food fish of Kumaun Himalaya inhabits in snow fed Rivers and also plays an important role in commercial fish production. Many teleos t fishes are reported to inhabit the Subhimalayan streams and rivers of India. These mountain streams are perennial shallow water bodies characterized by low temperature, high turbulent current and sandy rocky substratum 1 . To thrive successfully against th e action of strong water currents, many hill stream fishes demonstrate several unique adaptive modifications. The epidermis is the outermost defense organ against the surrounding aquatic environment comes into direct contact with mechanical hazard. The hil l - stream environs in the Kumaun Himalaya are unique in their characteristics inclusive of recent geomorphological transformations resulting from many multipurpose rivers, which are likely to adversely affect the overall health of hill - stream habitats. Such changing scenario will certainly have profound impact on the preferential distribution of the fish species and the nature of the external stimuli. Breeding tubercles are keratin - based epidermal nodules, which are found in at least 15 families of fishes in four orders. Breeding tubercles might offer a workable tool for examination of sexual selection among cyprinids. Material and Methods Live adult specimen of S. richardsonii ( a pproximate l ength 9 - 14 cm.) was collected from Kosi River at Hawalbagh distric t Almora. W ater current was very fast having velocity 0.5 to 2.0 m/sec. 2 . Specimen was maintained in laboratory at 25 ±2 0 C. The fishes were transferred from the site of collection to laboratory in well ventilated plastic containers and were kept for a perio d of about 5 - 6 days in glass aquaria having an artificially made rocky bed and aquatic vegetation grown therein. The aquaria were cleaned and supplied with fresh spring water on alternate days. The fishes were fed on aqua feed (tropical fish food). The fis hes were cold anesthetized following 3 for SEM preparation of snout. Tissues was excised and rinsed in 70% ethanol and one change saline solution to remove debris and fixed in 3% Glutaraldehyde in 0.1M phosphate buffer at pH 7.4 over night at 4 0 C at refri gerator. The tissues were washed 2 - 3 changes in phosphate buffer and dehydrated in ascending series of ice cold Acetone(30%, 50%, 70%, 90% and 100% approximate 20 - 30 min.) and critical point dried, using critical point dryer (BIO - RAD England) with liquid c arbon dioxide as the transitional fluid. Tissues were glued to stubs, using conductive silver preparation (Eltecks, Corporation, India) coated with gold using a sputter coater (JFC 1600) and examined in a scanning electron microscope (JEOL, JSM - 6610 LV) a nd the images were observed on the screen. Results and Discussion The skin of snout is scale less in Schizothorax richardsonii ( fig ure 1) and the epidermis is both types rough or keratinized and smooth or mucogenic. The smooth epidermis of snout possesses epithelial cells and mucous cells apertures intersperse between the epithelial cells in this fish. The surface architecture of the epithelial cells is characterized by the presence of a series of microridges separated by prominent irregular spaces. The mi croridges are compactly arranged, branched with abrupt ends of irregularly interwoven to form intricate mesh like pattern and interconnected with microbridges ( fig ure 2). The mucous cells, Research Journal of Animal, Veterinary and Fishery Sciences ___ _ _ ___________________________ ____ ___ _ ISSN 2320 – 6535 Vol. 1 ( 2 ), 1 - 4 , March (201 3 ) Res. J. Animal, Veterinary and Fishery Sci . International Science Congress Association 2 though distributed throughout the epidermis are in general, concent rated mainly in the outer layer of the epidermis often releasing their secretory contents profusely at the surface by a small pore. Interspersed between the epithelial cells, mucous cells are distinguished. Mucous cell openings, seen as wide, rounded apert ures or crypts, often containing blobs of mucus are interspersed between the epithelial cells. Generally, such apertures occur where the boundaries of three or more epithelial cells meet ( fig ure 3). In S. richardsonii the epidermis of snout possesses epide rmal tubercles (approximate length 128.888 µm). The base of each tubercle is rounded (approximate width 282.065 µm) ( fig ure 4, 5). Figure - 1 General view of S. richardsonii Figure - 2 SEMPH of the snout epidermis of S. richardsonii showing microridges interconnected with microbridges (Marked by arrows) (Scale bar - 5 µm) The skin of snout is scale less. Epidermis is smooth and possesses epithelial cells and mucous cell apertures between the epithelial cells. The epidermal cells at the surface of the sno ut investigated are composed of vertically compressed epithelial cells. It forms a continuous covering of the surface. It is interspersed with mucous cells opening to the surface. The primary function of the epidermis is protection against environmental ha zards. Figure - 3 SEMPH of the snout epidermis of S. richardsonii showing mucous opening (Marked by arrows) (Scale bar - 10 µm) Figure - 4 SEMPH of the snout epidermis of S. richardsonii showing epidermal tubercles (Marked by arrows) (Scale bar - 1 mm ) Figure - 5 SEMPH of the snout epidermis of S. richardsonii showing single epidermal tubercles (Scale bar - 100 µm) In fish, this function is generally attributed mainly to the gland cells secreting their contents on the surface. The large number of muco us cells in S. richardsonii suggests that the overall production of mucus in this fish is very high. This may be an adaptation to their peculiar bottom - scooping habit disturbing bottom mud more frequently in search of food, requiring Research Journal of Animal, Veterinary and Fishery Sciences ___ _ _ ___________________________ ____ ___ _ ISSN 2320 – 6535 Vol. 1 ( 2 ), 1 - 4 , March (201 3 ) Res. J. Animal, Veterinary and Fishery Sci . International Science Congress Association 3 increased efficiency i n the fish keeping its surface clean, mucus has remarkable power to precipitate mud held in suspension 4 . Thus the mucus secreted by the skin in the air breathing fishes may also serve to keep the skin clear for respiration. The abundance or dearth of the m ucous cells in the epidermis may also be correlated with their mode of life 5 . Mucus is secreted in receiving the necessary the stimuli from the surrounding environment, providing a sort of platform in the feeble adhesion, such neuromuscular organs have als o been reported in G. garhwali 6 . Kotrschal K. et al 7 and Mittal A.K. et al 8 . s uggested anti - viral, bactericidal and fungicidal effects of the secretion and found some role in defense and wound healing. The free surface of epithelial cells is bearing a seri es of microridges. The microridges are compactly arranged, branched with abrupt ends of irregularly interwoven to from intricate mesh like pattern and interconnected with microbridges. Interspersed between the epithelial cells, mucous cell apparatus distin guished on the snout epidermis. Sperry D.G. et al. 9 found no change of pattern after stretching fish oesophageal epithelium and suggested that spread of mucus from goblet (mucous) cells might be guided by the direction of ridges . Fish e lson L. 10 corr elated the variations in microridge patterns to locomotory activity and suggested that in faster swimming fishes, the most developed ridges served to trap mucus on the epithelial surface. Modifications in the pattern of microridges can also be caused by various i ntrinsic, e.g. hormonal 11,12 , or extrinsic factors e.g. temperature 13 , salinity 14 , mercury salts 15 , organic pollutants 16 , handling and ectoparasites 17 . Microridges have been reported to vary considerably in configuration and deposition, constituting varied patterns at different locations in different fish species and have been implicated to play variable roles. These include retaining mucus secretion to the cells surface, to increase the surface area for excretion and absorption through the skin, to facilit ate the spread of mucus away from mucous cells, to aid in producing laminar flow, to provide reserve surface area for stretching and to have their relation with the process of secretion at the cell apex. Kumari U. 18 suggested the microridges on the surface of the epithelial cells, like in the gills of other fish species, are after compactly arranged and organized into elaborate whorls forming intricate patterns. These structures providing mechanical flexibility and protection 19,20,21 . Whitear M. 17 suggested the mucogenic epidermis that form of the microridges is related to the process of secretion of slime. This could be considered as an adaptation to with stand mechanical stress and protect the surface of the fish, which has the characteristic habit of bott om dwelling furthermore, these microridges may gain a firm base and support from a dense network of fine filaments. The tubercles are found most often on males. The role and function of breeding tubercles are still uncertain. Breeding tubercles may be us ed for conspecific recognition 22 or for protection against mechanical injuries 23 . Müller G. et al 24 suggested that breeding tubercles may be used as weapons in intense pre - spawning male behaviour (defence of nests and territories). However, 25 proposed thos e tubercles originally evolved to allow breeding individuals to maintain close contact during spawning as a means to ensure fertilization of the eggs. Breeding tubercles may also act as hydrodynamic or tactile stimulators of females during courtship. In ro ach, breeding tubercles are presumed to give females detailed information about a male’s parasite load 26,27 and parasite resistance 28,27 and to act as a sexual ornament indicating his quality. Conclusion The present investigation has been designed to have a study of functional organization of the epidermis of snout of S.richardsonii . Snout epidermis is first come in contact with water current, especially when fish swims upstream and hence correlation has been made in relation to frictional. Habitat observa tions substantiate that there is a considerable relation between habitat characters (morphology and structure) of fishes. Acknowledgements I gratefully thank to College of Veterinary and Animal Sciences officer in charge and specially Mr. M. P. Singh the Staff electron microscope facility, G. B. Pant University of Agriculture and Technology, Pant Nagar (U.K.) for extending invaluable help incurring out SEM study. References 1. Nag T. C. and Bhattacharjee J., Retinal cytoarchitecture in some mountain - stream t eleosts of India, Environ. Biol. Fish, 63, 435 - 449 (2002) 2. Bhatt S. D. and Pathak J. K., Streams of Great Mountain are: Physiography and Physiochemistry. In: Ecology of the mountain water, Ashish publ. House N. Delhi, 43 - 58 ( 1991) 3. Mittal A. K. and Whitear M. A., Notes on cold anaesthesia of pokiolotherms, J. Fish. Biol . , 13, 519 - 520, (1978) 4. Hora S. 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