Bivalve mollusks Anadara kagoshimensis turned out to be able to endure high water salinity.

Specialists studied influence of increased salinity on composition of hemolymph – liquid, that circulate in vessels and intracellular hollows of mollusk Anadara kagoshimensis and also examined condition of “blood” cells – hemocytes, that fulfil function similar to blood corpuscle of vertebrates. Experiment, during which scientists adapted mussels to water with different salinity, showed that increasement of concentration of salt in water didn’t lead to significant decline in vitality of hemocytes and shift in composition of cells of hemolymph. The work of scientists demonstrates high tolerance of anadara to short-time maintenance in hypersaline environment. Results of their research are published in Fish & Shellfish Immunology.

Hypersalinity is a condition when water contains high concentration of salt. In soft reservoir concentration of salt is not high, and in hypersaline water the percent of dissoluted salt is 40% and higher. Hypersalinity is characteristic of salt lakes and bays where fresh water evaporates faster than new water manages to come.

Surplus content of salts can lead to distortions of salt balance (osmotic stress) in organism of water inhabitants, including bivalve mussels. It can influence cellular metabolism, concentration of intracellular fluid and cell size. Also, high salinity can lead to dehydration of cells, that negatively influences processes of growth, development and reproduction of mussels. In the process of evolution some kinds of bivalve mussels, including anadara, went through the process of development of specialized mechanisms of adaptation to high water salinity. Thanks to them mussels can regulate their metabolism and change behavior in order to survive in unfavorable conditions. The bivalve Anadara kagoshimensis is an invader and lives in the Black Sea from 50-ies of the previous century. As all bivalve mollusks, it can’t sustain the constant concentration of dissoluted substances inside cells and inside the organism when change of salinity of the environment takes place. However, these mollusks are able to adapt to changes of salinity thanks to intracellular reconstructions of systems of regulation concerning correlation of salts and water. These adaptations on the cellular level are followed by unique significant reconstructions of physiology of cells of the organism.

Scientists from Laboratory of ecological immunology of aquatic organisms, A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS (Moscow) and Department physiology and biochemistry of animals of A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS, Russia (Moscow) studied the influence of high water salinity on cell composition of hemolymph – liquid that fulfils transport and protective functions in organisms of bivalve mussels. In the course of the experiment biologists placed mussels in water, where salt concentration was gradually increased from 18% to 35% and 45%, and maintained them in these conditions during two days. Researchers found out that maintenance in environment with salinity of 35% changed structure of red blood cells and reduce their diameter. During staying in environment with salinity 45% they observed increasement of size of cells of hemolymph. However, it was stated that staying in hypersaline water didn’t lead to death of blood cells of the ark shell.

Results of the research showed that A. kagoshimensis had high tolerance to short-time influence of high salinity of water. Scientists suggested that in the base of high adaptive potential of anadara to hypersaline environment lied intracellular reconstructions, that took place, in particular, in hemocytes. At the same time direct mechanisms and ways of cell stability to osmotic stress need further researches on the base of tolerant kinds of bivalve mollusks.