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

地球上的生物在进化过程中不断获得对紫外线的防御功能。哺乳动物的防御功能大致分为体毛特征型和表皮组织特征型。我国野生动物鼠兔、黄鼠、沙鼠和花栗鼠的体毛具有双色分层现象。本研究发现，Wistar大鼠体毛下部黑色较白色毛明显吸收紫外线（UV）能量，体毛特征型的双色结构对UV有较好的防护作用。与Wistar大鼠相比，野生动物由于体毛的双色结构而病变较轻，有炎性细胞浸润、水肿、结痂和纤维化。在这些野生动物中，毛发紫外线透过率与表皮、居住地紫外线强度呈负相关。不同物种的毛的长度和密度不同，其对紫外线的防御效果也不同，这主要取决于居住地的紫外线强度，环境因子中的气温不仅决定了它们对紫外线的防御形式，也决定了它们对紫外线的防御强度。因为在炎热的环境中长头发会妨碍热量的散失。以荒漠地区的黄鼠为例，其毛长较短，但表皮较厚，以抵御紫外线，不同物种对紫外线的防御能力季节性变化差异不显著，野生动物对紫外线的防御能力与生境条件、毛的颜色、毛的长度、密度、表皮的厚度、皮肤的颜色相对应。

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.