MECHANISMS UNDERLYING EVOLUTIONARY AND ON TOGENIC TEMPERATURE ADAPTATIONS OF METABOLISM IN POIKILOTHERMS

A higher respiration rate in fish occurring at low environmental tempe ratures is provided mainly by a higher concentration of mitochondria i n their skeletal muscle. The compensatory increase in the respiration rate and in the concentration of mitochondria as a metabolic phylogene tic adaptation allows to dwellers of high latitudes to provide vor ene rgy supply in a required volume at the extremely low environmental tem peratures. Ontogenetic adaptations of fish to low environmental temper atures are expressed, like the phylogenetic adaptations, in compensato ry increase of cytochromes, activity of mitochondrial enzymes and, fin ally, rise of the concentration of mitochondria in the skeletal muscle . Similar results of phylogenetic and ontogenentic adaptations to low environmental temperatures is due lo basically different mechanisms.