Hemolymph cellular composition, morphology and functional properties of the Pacific oyster (Crassostrea gigas) hemocytes were studied. Three hemocyte types (agranulocytes, hyalinocytes and granulocytes) were described in hemolymph. The morphology of each type was characterized by light microscopy and flow cytometry. Agranular cells (agranulocytes and hyalinocytes) were the dominant type of cells in hemolymph; their number was 86.7±2.7% of total cell count. Under hypoxia the number of agranulocytes increased (37.4% for control group versus 95.3% for hypoxic probes), whereas granulocyte and hyalinocyte number decreased up to 3.9% and 0.7% in hypoxic specimens respectively. The spontaneous ROS production decreased in each hemocyte type after exposure to hypoxia. Low dissolved oxygen did not influence hemocyte proliferation and mortality level.

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Seascape complexes are decisive in choosing of technologies for growing different species of fish and mollusks, as well as in designing and installing farms on the Black Sea shelf. Marine farms, as hydrotechnical installations, play the role of artificial underwater seascapes and have a mutual influence on natural local systems. This article describes the main elements of mussel-oyster farms, the criteria for choosing a location for them, technological solutions of anchor systems, taking into account the peculiarities of the marine seascapes of the Crimean peninsula. In the Black Sea, it is advisable to install farms of the long-line type, which satisfy almost all the requirements for growing mollusks: they are quite stable during strong storms and wind impacts, allow changing the depth of mollusk placement if necessary, and are easy to install and maintain. The depths at the site which was selected for the installation of the marine farm should be in confines 10...30 m, and 15...20 m is the optimal depth for it. The permissible depth must be at least 10 m under the marine farm in consequence. The choice of optimal depths is associated with the need to save materials also. The characteristics, applicability and installation features of several types of anchors (concrete, screw and plow) for grounds of different composition and density are proposed. Promising areas for the development of the Black Sea mariculture are the western and eastern coasts of the Crimean peninsula.

To understand the role that hemocytes play in processes of cellular immunity of bivalve mollusks, they should be accurately classified based on their morphological and physiological characteristics. The circulating hemocytes of the cultured Pacific oyster (Crassostrea gigas) and marine mussel (Mytilus galloprovincialis) were investigated using light microscopy and flow cytometry. In the mussel, two cell types, granulocytes and agranulocytes, were identified based on the presence of two subpopulations of cells differing by size and granularity level on light scatter plots. Light microscopic examination confirmed the presence of cells with cytoplasmic granules and cells without granulation in hemolymph of the mussel. In the oyster, light microscopy and flow cytometry revealed three types of hemocytes: agranulocytes, hyalinocytes, and granulocytes. The cells in the hemolymph of both species were mainly represented by agranular cells, which constituted 78.4 ± 8.9 % in the mussel and 86.7 ± 2.7 % (agranulocytes and hyalinocytes) in the oyster. Agranulocytes were the smallest cell type in the mussel and oyster. They were round-shaped and had large nuclei and narrow cytoplasm. Hyalinocytes of the oyster were larger and irregularly shaped, with eccentric nuclei. Granulocytes of both species contained numerous eosinophilic, basophilic, and mixed granules and formed pseudopodia. Flow cytometry showed that the agranular hemocytes of both species produced considerably fewer reactive oxygen species compared to granulocytes. Morphological and functional characterization of hemocytes of cultivated species improves the analysis of physiological state of bivalve mollusks farmed in the Black Sea region