Fever in the lizard Dipsosaurus dorsalis

Abstract

FEVER is considered to be a universal response of warm-blooded animals to endotoxins¹. Although during a fever a mammal uses behavioural as well as physiological means to increase its body temperature², 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 gradient³. If this lizard is placed in a temperature chamber in which one end is heated to above the animal's 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 sides⁴. 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^5,6, and lesions in the posterior hypothalamus in both lizards⁴ and mammals⁷ lead to an inability to maintain a high body temperature.