Histological characteristics of hair follicle pattern in Indian bison (Bos gaurus), black buck (Antelope cervicapra) and nilgai (Boselaphus tragocamelus)

Abstract

Background and Aim: Indian bison, Black buck and Nilgai are in danger of extinction because people are hunting them for their meat and horns for sports, trophies etc. These animals are also protected under International Union for Conservation of Nature and Natural Resources (IUCN) and Conservation on International trade in Endangered Species of Wild Fauna and Flora (CITES). Taking note of the vulnerability of these animals to extinction, we characterized the hair follicle pattern of these animals for future reference. This study included a total of 30 skin samples comprised of 8 samples of bison, 10 samples of black buck and 12 samples of nilgai. Materials and Methods: Skin samples were obtained from Sri Jayachamarajendra Zoological Park, Mysore, Karnataka, India and Bannerghatta Biological Park, Bangalore, Karnataka, India and also from confiscated skins from forest and police officials of Karnataka. The skin samples were processed and horizontal section of 6-7 µm thickness was used for the routine histological technique using different special staining techniques. Observation such as hair follicle pattern, sebaceous glands and sweat glands distribution, blood vessels, nerve fibre, collagen and elastic fibres were noted. Results: In the bison, compound hair follicles were uniformly distributed and were rectangular in shape comprising of a primary hair follicle associated with 3-4 secondary hair follicles in addition to their sebaceous glands. Uniformly distributed coiled tubular sweat glands were also noticed which were lined by simple cuboidal epithelium. In the black buck, the compound hair follicles were densely distributed and were arranged linearly in the dermis of skin. Within the compound follicle, linear arrangements of primary and secondary follicles were observed. Each primary hair follicle was supported by 24 secondary hair follicles and the primary hair follicle was always present at the centre when it was present with 2 secondary hair follicles. In nilgai, the compound hair follicles were densely distributed in the dermis of skin. The primary hair follicles were bilaterally surrounded by 2-3 secondary hair follicles. Each primary and secondary hair follicle was associated with sebaceous glands. Conclusion: The histological pattern of the hair follicle data was established and the hair follicle pattern will be of use in the identification of the wild ruminant skins which are commonly poached by the poachers. It will also be useful to compare the histological characteristics amongst the wild ruminants.