Temperature acclimation modulates the oxygen binding properties of the Atlantic cod (Gadus morhua L.) genotypes-HbI*1/1, HbI*1/2, and HbI*2/2-by changing the concentrations of their major hemoglobin components (results from growth studies at different temperatures).

The influence of long-term acclimation temperatures in Atlantic cod (Gadus morhua) was studied by growth experiments carried out over a total of 272 individuals. The attention focused on the structural and functional modulation of the five electrophoretically distinguishable genotypes of cod hemoglobin (HbI*1/1, HbI*1/2, HbI*2/2, HbI*1/2b, and HbI*2/2b) and on the correlation with body length/weight. The main results can be summarized as follows. (1) Acclimation to lower (4 and 8 degrees C) and higher (12 and 15 degrees C) temperatures favors the expression of, respectively, more anodic and more cathodic hemoglobin components. (2) The optimal O(2) transporting features are observed at 12 degrees C, as well as a saturation-dependent temperature dependence of O(2) binding, which furthermore is strongly dependent upon the acclimation background. (3) The optimal growth condition for the three main genotypes (HbI*1/1, HbI*1/2, and HbI*2/2) is associated with T=12 degrees C. The overall results are consistent with the idea that environmental temperatures constitute a primary factor in the aggregation of individuals physiologically more than genetically homogeneous. This is fully confirmed by careful statistical analysis carried out over a subset of individuals for which the full set of structural (isoelectric focusing), functional (O(2) binding), and growth data was available.