Seasonal Changes in Hemolymph Parameters of the Bivalve Modiolus kurilensis Bernard, 1983 from Vostok Bay, Sea of Japan

Hemolymph is one of the main tissues providing invertebrates’ immunity and homeostasis. Earlier, we showed that some of the hemolymph immune parameters of the common Far Eastern mollusk Modiolus kurilensis are sensitive to bacterial and anthropogenic challenges. In this work, a number of cellular parameters such as total hemocyte count (THC), hemocyte phagocytic activity (PA), and reactive oxygen species (ROS) and humoral parameters such as hemagglutination (HA) and hemolytic (HL) activity of plasma, as well as its protein concentration (C_P) and profiling in M. kurilensis were studied depending on the season and environmental indicators (temperature, salinity, and oxygen concentration). The total hemocyte count was weakly correlated with water oxygen concentration (R = –0.25) and temperature (R = 0.27), and the 36 kDa plasma protein was weakly correlated with temperature (R = –0.33). Also, there was a correlation (R = 0.38) between hemagglutination activity and the 19 kDa protein fraction. The minimum values for a number of parameters were noted in January (THC, PA, ROS, HA, HL), while the maximum values were observed in late spring (THC, PA, ROS, HA, HL). At the same time, in other months, these and most other parameters had metastable values. Thus, the indicators that were identified in previous studies (THC, PA, ROS, HA, HL, C_P, protein fractions 55 and 124 kDa) are suitable for assessing the physiological state of M. kurilensis during most of the year.