AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 1 157-R161, Copyright © 1982 by American Physiological Society
Metabolic and acid-base changes during selection of warmer water by cold-acclimated fish
L. I. Crawshaw, R. A. Ackerman, F. N. White and M. E. Heath
Largemouth bass (Micropterus salmoides) acclimated to 3 degrees C were
placed in a thermal gradient. The bass selected the final thermal
preferendum of 28 degrees C in about 18 h. The movement into warmer water
was initially rapid but became progressively slower. 2) Other bass were
acclimated to 8 degrees C, cannulated in the dorsal aorta, and placed in a
temperature-controlled chamber. Oxygen uptake, blood pH, and total CO2 were
measured as the chamber temperature was increased to 28 degrees C following
a time course similar to that followed by bass in the gradient. 3) Oxygen
uptake was always elevated above the resting level, and this elevation
increased as higher temperatures were encountered. 4) Just prior to
placement in the chamber the pH of the arterial blood was 7.98 +/- 0.05
(mean +/- SE). As the temperature was increased neither the pH nor the
total CO2 content of the blood exhibited major changes. At temperatures
between 26 and 28 degrees C, the pH (8.01 +/- 0.03) was about 0.3 pH units
above predicted normal values. 5) During the return to the final thermal
preferendum fish experience overall metabolic rates and extracellular
acid-base levels that deviate progressively farther from normal resting
levels. Neither factor appears likely to be the major determinant of the
behavioral response.
