ADAPTATION OF ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906) TO HYPO- AND HYPEROSMOTIC ENVIRONMENTAL CONDITIONS: HEMOCYTE RESPONSE

Abstract

Anadara kagoshimensis (Tokunaga, 1906) is an invasive species that has successfully colonized the waters of the Black Sea and the sea of Azov, despite the significantly lower salinity level of these waters in comparison with the native region. The morphological and morphometric characteristics of bivalve mollusk A. kagoshimensis erythrocytes were analyzed by light microscopy during adaptation to hypo- and hyperosmotic experimental conditions. The control group of mollusks was kept at 18‰ salinity. Experimental groups were acclimated to 8, 14, 35 and 45‰ salinity. A decrease of salinity was achieved by diluting seawater with distilled water at a rate of 1.5±0.5‰ per day. Sea salt was added to each aquarium to increase salinity. Salinity was increased at a rate of 2.5±0.5‰ per day. Exposure period was 2 days. It has been shown that the salinity range of 14-35‰ is natural for ark clam. No significant changes in cell morphology were observed under these conditions. At the same time, environmental salinity levels of 8 and 45‰ caused obvious stress: cellular anomalies appeared, and the linear characteristics of erythrocytes were changed. However, cell lysis did not occur, the values of the specific surface area and nuclear-cytoplasmic ratio did not change. The results of the present work indicate the ability of the arc clam to exist for some time in regions with extremely low and high salinity of the aquatic environment.