ニホンジカ袋角における体温調節作用とその特異性

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The antlers of deer have been developed in size and shape through a progressive evolution as forest-dwelling ruminantia. Concerning the function of antlers, many opinions which have a relation to life in the herd at the breeding season have been reported. These discussions, however, referred mainly to the significance of completed antlers other than a few observations on velvety antlers. The present study was conducted to obtain data for a discussion of the physiological function of velvety antlers, in which a consideration that the antler in the process of growth seems to affect the thermoregulatory function of the brain and the body in the summer time is also contained.<BR>1. A two year-old male of the Japanese deer which had growing antlers was used as the experimental animal. The surface temperature of the velvety antler and the body was measured at several positions in specially prepared room of which the temperature was controlled so as to rise from 0°C to 33°C and then fall to 19°C within about 7 hours. The examination was done twice, and similar results were obtained. 2. The temperature of the velvety antlers changed from 5°C to 36.5°C. When the environmental temperature start to rise, the antlers' temperature increased, while when the former started to fall the latter decreased. 3. The temperature responses of the shank and ear against the changes of environmental temperature yielded an S-shaped curve, but the antler temperature increased or decreased in parallel with the environmental temperature. 4. During immersing the velvety antler in stirred ice water, the temperature showed the hunting temperature reaction at intervals of 10-20 minutes with 1-3°C amplitude. 5. For purposes of anatomical and histological observations of the blood supply in the velvety antlers, heads of 2 cases — one is used in this experiment and, another one is also a Japanese deer with velvety antlers, were used. The morphological observation showed that the venous blood returned from the velvety antler by four pathways of which the two veins drained through the cavenous sinus. 6. From these results it is considered that the velvety antlers seem to have a thermoregulatory function. They appear to serve as a thermoregulatory organ to the brain, especially, they act effectively when a sudden change of environmental temperature occurred.<BR>This probable thermoregulatory function of the velvety antlers suggests that it is important for maintenance of the individual during summer time, and it is also suggestive to the evolutionary history of the deer in northern environments in which the daily or seasonal variation in air temperature is very severe.
日本哺乳類学会の論文

ニホンジカ袋角における体温調節作用とその特異性

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