[Morphologic aspects of cardiac myocyte differentiation in Black Sea--Sea of Azov sturgeon (Acipenser güldenstädti colchicus V. Marti)].

Processes of ultrastructural organization of cardiac myocytes have been studied in the Russian sturgeon (Acipenser güldenstädti colchicus V. Marti) during germinal, prelarval, larval periods of development and in mature specimens. One of the main peculiarities of early cardiogenesis in this representative of Chondrostei fishes is a prolonged, observed during germinal and early prelarval periods, repression in multiplication of myocardial cells. Decreasing amount and size of yolk platelets in cytoplasm of these cells at the end of the germinal period could be connected with their intensive specific differentiation and increasing functional activity. Accumulation of free lipids during this period and their decreasing contents in early prelarval period demonstrate a certain transition to another way of metabolism. The data obtained on ultrastructure in mature specimens corresponds mainly to modern ideas on organization of the cardiac muscular tissue in other species of lower vertebrates.