Fever and survival: the role of serum iron.

1. The effects of bacterial infection and temperature on serum iron levels were investigated in the lizard Dipsosaurus dorsalis. 2. Changes in body temperature from normal (38 degrees C) to febrile (41 degrees C) did not alter serum iron levels. Injection with Aeromonas hydrophila led to a significant reduction in serum iron levels, comparable to that found in mammals. This reduction in serum iron level was independent of the lizard's body temperature. 3. When grown in vitro, A. hydrophila grew equally well at afebrile (38 degrees C) and febrile (41 degrees C) temperatures. When the iron levels of the growth medium were reduced, the bacterial growth was diminished at the febrile temperature but was not significantly affected at the afebrile temperature. 4. The addition of iron supplements to bacterially infected lizards led to an increase in the percent mortality. 5. These results indicate that one of the mechanisms behind the beneficial, or adaptive value of fever in D. dorsalis is the decrease in iron available to the pathogenic micro-organisms.