Fever in the Lizard \u3cem\u3eDipsosaurus dorsalis\u3c/em\u3e

FEVER is considered to be a universal response of warm-blooded animals to endotoxins. Although during a fever a mammal uses behavioural as well as physiological means to increase its body temperature, it is not known whether fever develops in an animal such as a lizard which regulates its body temperature largely by behaviour. For example, the desert iguana (Dipsosaurus dorsalis) regulates its body temperature close to 38.5° C if placed in a chamber with a temperature gradient. If this lizard is placed in a temperature chamber in which one end is heated to above the animal\u27s lethal body temperature (50° C) and the other end is maintained at room temperature, the lizard regulates its temperature by moving back and forth between the two sides. Under these conditions, one can determine its high and low set-points (Fig. 1). The central nervous control of temperature in an ectotherm, such as a lizard, and an endotherm, such as the rabbit, appears to be quite similar. For example, both possess a hypothalamus which is thermally sensitive, and lesions in the posterior hypothalamus in both lizards and mammals lead to an inability to maintain a high body temperature