Fever in goldfish is induced by pyrogens but not by handling

Six goldfish, Carassius auratus, weighing 2.5 to 4 g were placed individually in an aquarium with two communicating chambers. One chamber was thermostatted at 34 degrees C, the other at 37 degrees C. In control Session a, without external intervention, fish selected the cooler chamber most of the time and stayed only 4.8 +/- 1.1 min/2 h at 37 degrees C. In Session b, infectious fever was assayed: pyrogen (Salmonella typhosa LPS, or human interleukin-2) was injected intracranially and fish stayed 44.7 +/- 15.3 min/2 h at 37 degrees C. In Session c, behavioral stress was achieved by chasing the fish with a net, catching it, handling it out of water, and injecting 10 microL of saline intracranially. Fish stayed 2.7 +/- 1.0 min/2 h at 37 degrees C. Analysis of variance showed that stay at 37 degrees C was significantly longer in Session b than a and c, and that Sessions a and c were not significantly different from one another. This result confirms the existence of behavioral fever, but does not support the hypothesis of fever in fish after handling.