Erythroid elements of the hemolymph of the bivalve mollusk Anadara kagoshimensis (Tokunaga, 1906) under conditions of hydrogen sulfideloading: flow cytometry, light-optical microscopy
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Abstract
An imbalance between organic matter oxidation and oxygen supply leads to the formation of persistent redox zones in the water column. On the shelf, this typically occurs due to the absence of full vertical convection, and the formation of localized decay zones of dead organic matter. The functional mechanisms of the resistance of a number of benthic organisms to such conditions are of significant interest. This study investigates the bivalve mollusk Anadara kagoshimensis (Tokunaga, 1906), known for its tolerance to hydrogen sulfide contamination. Using flow cytometry and light microscopymethods , we examined the effects of hydrogen sulfide impact on the morphofunctional characteristics of the mollusk's erythroid cells under experimental conditions. The study was performed using adult specimens with the shell heights of 23–34 mm. The control groupof mollusks was maintained in the aquarium with oxygen concentrations of 7.0–8.2 mg O₂ L⁻¹ (normoxia). For the experimental group, the oxygen concentration was first reduced to 0.1 mg O₂ L⁻¹ over 2 hours (via nitrogen bubbling), subsequently following by adding Na₂S to reach a final concentration of 6 mg S²⁻ L⁻¹. Exposure to hydrogen sulfide revealed a significant increase in the volume of Anadara's hemolymph erythroid cells (>40%, p < 0.01), accompanied by a substantial rise in fluorescence intensity of rhodamine R123 and 2-7dichlorodihydrofluorescein diacetate (DCF-DA) (2-3 fold, p < 0.01). This indicates enhanced oxidative processes within the cells and their potential lysis; the latter may facilitate the release of hematin-containing granules capable of neutralizing sulfides. This observed response appears to be adaptive. Increased side scatter (SS) and SYBR Green fluorescence demonstrate a rise in granular inclusions within the red blood cells under hydrogen sulfide exposure as well as heightened functional activity of their nuclei.