Toxicological assessment of inorganic arsenic: Bioaccumulation and immunotoxicity in Acanthopagrus schlegelii

Inorganic arsenic contamination in the marine environment can have adverse effects on aquatic animals. This study investigated the toxicity of trivalent As (III) and pentavalent As (V) in Acanthopagrus schlegelii by analyzing tissue bioaccumulation and non-specific immune responses. Fish were exposed to dietary As (III) or As (V) at 0, 5, 10, and 15 mg kg⁻¹ for 28 d. The total arsenic (TAs) accumulation (mg kg⁻¹ wet weight) was highest in the liver (4.26–8.87), followed by the muscle (2.13–2.88), intestine (0.97–2.02), and blood (0.30–0.89) at the end of exposure. During the exposure, inorganic arsenic was detected in the liver (0.05–0.06), blood (0.07–0.16) and intestine (0.05–0.36), whereas no accumulation was observed in muscle. The accumulation of arsenobetaine (AsB) was slightly lower than that of TAs across all tissues. Arsenic bioaccumulation in all tissues was not directly proportional to the levels of inorganic arsenic exposure, as both As (III) and As (V) were rapidly biotransformed into less toxic AsB, indicating normal arsenic metabolism in black seabream. Moreover, a two-way MANOVA analysis revealed that the bioaccumulation of all arsenic species differed significantly among tissues and between two arsenic exposure forms. In terms of immunotoxicity, dietary exposure to As (III) and As (V) significantly suppressed nonspecific immune responses in leukocytes, with marked reductions in phagocytic rate, phagocytic index, and respiratory burst activity observed from 7 d onward. These findings enhance the understanding of arsenic bioaccumulation and immunotoxicity in marine fish and provide important data for the risk assessment of arsenic contamination in aquaculture feeds.