Comparative Aspects of the Study of Morpho-physiological and Biochemical Parameters of Somatic Growth in Populations of Two Species of Black Sea Bivalvia Mollusks — <i>Cerasoderma glaucum</i> and <i>Flexopecten glaber ponticus</i

Presented are the results of the analysis of the morpho-physiological and biochemical indicators of somatic growth in the Black Sea bivalve mollusks, the cockle Cerastoderma glaucum (Bruguiere, 1789) and the scallop Flexopecten glaber ponticus (Bucguoy, Dautzenberg et Dollfus, 1889), living in the vicinity of Sevastopol. The examples are of three size-age groups, in the length range from 12 to 30 mm for both species, the features of tissue biosynthesis (somatic growth) of soft tissues were studied. According to the total RNA content and the RNA/DNA index in the C. glaucum, it was shown that in the groups 17–22 and 23–28 mm (age two–three years), the level of synthesis of protein structures is 1.3–1.7 times higher than in the underyearlings. In individuals of the F. glaber ponticus with linear sizes of 13–17 and 21–24 mm (underyearlings), the level of synthesis of protein structures was 1.2–1.5 times higher than in larger individuals (age two years). The species specificity of somatic growth was most significantly manifested in the middle and older size groups of the studied mollusks. The values of biochemical growth parameters in both species indicated an average level of tissue growth in comparison with other previously obtained data for the mass Black Sea bivalves. Linear regression models of size-weight values showed that for both species, the change in size explains 62–86% of the variation in body weight of the mollusk. Analysis of weight parameters (total mass/soft tissue mass) indicates a positive allometry of somatic tissue growth.