Resistance to negative effects and the ratio of energy metabolism enzyme activity in tissues of the Black Sea molluscs Mytilus galloprovincialis Lamarck, 1819 and Anadara kagoshimensis (Tokunaga, 1906)

Determining the ratio of energy metabolism enzyme activity of malate dehydrogenase (MDH, 1.1.1.37) and lactate dehydrogenase (LDH, 1.1.1.27) allows getting the cumulative assessment of the physiological condition of the object of study in response to the impact of different nature. The aim of the study was to compare the change of value of MDH/LDH ratio in the tissues of bivalve molluscs: native mussel Mytilus galloprovincialis and successful invader Anadara kagoshimensis – in laboratory conditions under the effect of hypoxia, anoxia, PCBs, hydrogen sulfide contamination and long-term maintenance in the aquarium without feeding. Sexually mature molluscs were collected near Sevastopol. Shell length of a mussel was 45–62 mm, of anadara – 27–49 mm. Enzyme activity was measured spectrophotometrically (at 340 nm and 25 °C) by the rate of NADH oxidation in the cytoplasm of tissues (muscles, hepatopancreas, gills). Under the effect of negative factors, as a rule, LDH activity decreased significantly (by 36–80 %), MDH activity remained stable, and MDH/LDH ratio in the tissues of both species of molluscs increased 1.5–4 times. However, in the tissues of hemoglobin-containing anadara the ratio was 10 times lower than that of mussels, both in control and in the experiment. Comparison with literature data showed that tolerant to hypoxia mollusc-invader had the same low MDH/LDH ratio as oxyphilic hydrobionts: scallop Mizuhopecten yessoensis (Jay, 1857), crustaceans Crangon crangon (Linnaeus, 1758) and Carcinus aestuarii Nardo, 1847. Apparently, the low MDH/LDH ratio reflects the ability of anadara to maintain a high level of oxidizing processes in the tissues due to the content in them of a significant pool of erythrocyte hemoglobin, carotenoids, glutathione, which support the aerobic process and implement antioxidant protection. The ratio of the activity of MDH/LDH can be used in monitoring studies to assess the degree of oxygenation of molluscs tissues in normal and hypoxic conditions of different origin.