Mechanisms of temperature acclimation in the carp: a molecular biology approach.

Most fish are unable to regulate their body temperature. Therefore their muscle power output would be expected to decline markedly with decreased environmental temperature. However, some species including carp show a remarkable ability to acclimate. The nature and significance of changes in enzymatic myosin ATPase activity and the recruitment of different muscle fiber types in relation to acclimation and environmental temperature in carp are reviewed. These changes presumably involve qualitative and quantitative changes in gene expression. To approach the problem, we have constructed a carp genomic library and isolated 28 nonoverlapping clones containing sequences of different myosin heavy chain (MHC) isoforms along with a clone containing carp actin sequences. Plasmids containing probes specific for a carp fast muscle MHC and actin RNA were constructed. Hybridization results suggest that the expression of this MHC isoform RNA is increased in warm- relative to cold-acclimated carp. These data indicate that there are different MHC isoform genes that are expressed at warm and cold environmental temperatures.