Effect of rapid temperature change on mean body temperature and gill ventilation in carp.

Carp were transferred from 25 degrees C water to a calorimeter at 15 degrees C or from 15 degrees C water to a calorimeter at 25 degrees C. During cooling, dorsal muscle temperature (Tdm) and mean body temperature (Tb) were continuously monitored. During the first minutes Tb changed rapidly, while Tdm changed only slightly. In a 0.468-dg fish, Tdm decreased to two-thirds of the final value in 8.05 min, while Tb attained this value in 3.6 min. Tdm changed faster during heating than during cooling. Carp were also placed in a device where gill ventilation (VG) could be continuously monitored while rapid shifts in the temperature of the inspired water (TPINSP) AND/OR BODY SURFACE (Tbs) were effected. Changing Tinsp and Tbs both effected rate-sensitive changes in VG, although Tinsp was more effective. Decreases in Tinsp or Tbs produced decreases in VG; increases in Tinsp or Tbs had an opposite effect. The fish respiratory system is sensitive to the rate of change of external temperature. This sensitivity provides evidence for the existence of peripheral thermal input to the systems regulating respiration in teleost fish.