The effect of hydrogen sulfide loading (SL) on the morphometric characteristics of erythroid elements of the Anadara kagoshimensishemolymph (Tokunaga, 1906) was studied experimentally. The work was conducted on adult mollusks with a shell height of 26-38 mm. The control group of mollusks was kept in an aquarium with an oxygen concentration of 7.0–7.1 mgO2 l-1 (normoxia). The experimental group was exposed to SL, which was created by dissolving the Na2S donor in water to a final concentration of 6 mgS2- l-1. A day later, the oxygen level in the water amounted to 1.8 mgO2 l-1, and hydrogen sulfide was not detected. A part of the mollusks was subjected to repeated SL by adding Na2S to a final concentration of 9 mgS2- l-1. By the end of 2 days, 1.9 mgS2- l-1 and trace oxygen concentration (0.03 mgO2 l-1) were recorded in the water. Under conditions of short-term hydrogen sulfide load (1st day), the population of erythroid elements of Anadara became more heterogeneous. The content of micro- and macrocytes in the hemolymph increased, the number of cells with modified shape and low content of granular inclusions in the cytoplasm rose. The number of free hematin granules in the hemolymph, on the contrary, significantly increased. The mean cell volume (Vc) increased by more than 20%. Staying in conditions of increased concentration of sulfides for 2 days led to a significant decrease in Vc, which is determined by a significant reduction in the population of macrocytes in the hemolymph of mollusks.