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Researchers have investigated ultrastructural and biochemical changes in response to thermal acclimation in the cardiac ventricle of striped bass. It was found that ventricular mass and ventricular mass divided by body weight were considerably higher in bass acclimated to cold than those living in warm temperatures. Ventricular enlargement did not have an impact on volume densities of myofibrils, mitochondria, citrate synthase activity or protein concentration. It is assumed that larger size of the cardiac pump and compensation of its metabolic capacity during cold temperature adaptation play a role in maintaining perfusion of the systemic vasculature with blood rich in oxygen and nutrients.

Researchers have attempted to resolve the debate about whether the intracellular oxygen-binding protein myoglobin (Mb) is functional in antarctic icefishes by comparing mechanical performance of isolated, perfused hearts from two hemoglobinless species of the icefish family. One species expresses Mb and the other does not. Data was obtained which strongly supports the view that Mb is functional, playing a role in the support of mechanical performance of hearts from antarctic icefish species where the protein is expressed.

The effect of high lipid content on the rate of oxygen diffusion in fish skeletal muscles was investigated in the striped bass. High lipid content was observed in oxidative muscle tissues during acclimation from 25 to 5 degrees Centigrade. The increase enhanced the transport of oxygen across the membranes, suggesting that thermal acclimation is accompanied by oxygen solubility in the muscle tissues.

The study of striped bass oxidative red muscle reveals that enhanced carnitine palmitoyltransferase I activity and carnitine concentrations increase the muscle capacity for fat oxidation in cold-acclimated conditions. Red muscles also exhibit fiber mass and mitochondrial density higher than normal levels. The mechanisms may help overcome the lower metabolic rates caused by low temperatures.

Peroxisomal contribution to fatty acid oxidation in a temperate teleost, the longhorn sculpin, was measured. Substrate oxidation estimates were correlated to the quantitated maximal activities of carnitine palmitoyltransferase and acyl CoA oxidase over various fatty acyl substrates. Results indicate that the beta-oxidation of most of the polyunsaturated fatty acids and 50% of palmitoyl in the tissue were caused by the hepatic peroxisomes of the teleost.