Ultraviolet permeability through skin of wild animals and skin degeneration by ultraviolet rays

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The living being on earth has been acquiring defense function to ultraviolet rays in process of evolution. The defense function of mammalian is classified roughly in body hair characteristic type and cutis organization characteristic type. Wild animals of Pika, Yellow rat, Jird and Asiatic chipmunk in China have a two colors stratification of body hair. In this study, the black lower part of body hair absorbed significantly ultraviolet rays (UV) energy in comparison with white hair in wistar rat, and the two colors structure of body hair is effective function to protect the skin from UV for the body hair characteristic type.On the skin tissue lesions induced by UV-B irradiation, the wild animals were light lesion due to the two colors structure of body hair compared with wistar rat with inflammatory cell infiltration, edema, crust formation, and fibrosis.In these wild animals, negative correlation was recognized during ultraviolet permeability through body hair with epidermis and UV intensity in habitation. The defense effect to UV in each species was different depend on UV intensity in habitation by reason of difference of length and density of hair in each species.Air temperature in environmental factor is important to decide the defense form to UV as well as UV intensity. Because long hair disturbs heat loss in hot environment. For example on yellow rat inhabited near desert, the hair length is short, but epidermis is thick for defense to UV.On the other hand, seasonal variation of defense ability to UV was no statistical significance in each Species.Wild animals keep effective defense function to UV corresponding to habitat condition with color, length and density of hair and thickness of epidermis and skin color.