Effects of altering spinal cord temperature on temperature regulation in the Adelie penguin,Pygoscelis adeliae

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Abstract
In 6 Adelie penguins, thermodes were implanted in the cervical and upper thoracic spinal canal. At thermoneutral (+ 8 to + 16° C) and cold (−18 to −22° C) ambient conditions, the effects of spinal canal heating and cooling on the surface temperature of one flipper (skin blood flow), oxygen consumption (metabolic heat production) and esophageal (core) temperature were observed in the conscious animals.—At thermoneutral ambient conditions, spinal cord cooling reduced and spinal heating increased skin blood flow. Only very strong spinal cooling induced small increases of oxygen consumption, while spinal heating had no effect at all. The relation between spinal canal temperature and metabolic heat production at thermoneutral ambient conditions could be described by a linear regression with a slope of −0.05 W · kg−1 · °C−1.—At cold ambient conditions, the skin vessels of the flippers were permanently constricted and an increase of metabolic heat production by 5–50% of the resting rate developed within 1–3 h of cold exposure. Spinal cord cooling augmented metabolic heat production. Spinal heating reduced heat production but did not release skin vasoconstriction even at high stimulus intensities. The relation between spinal canal temperature and metabolic heat production in the cold could be described by a linear regression with a slope of −0.52 W · kg−1 · °C−1.—It is concluded that temperature sensors with specific functions in temperature regulation are located in the spinal cord of the Adelie penguin. These sensors contribute to the central temperature signal input in the hypothermic and hyperthermic ranges of core temperature. The peripheral thermal conditions strongly influence the responsiveness of the various thermoregulatory effectors to the spinal thermal stimulus.

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