Ecotoxicity of polyhexamethylene biguanide hydrochloride (PHMB) in the neotropical snail Biomphalaria glabrata (Say, 1818)

The polyhexamethylene biguanide hydrochloride (PHMB) is a sanitizer with a broad range of potential applications. Nevertheless, the ecotoxicity of PHMB to gastropod snails remains scarce. Thus, the current study aimed to assess whether the exposure of freshwater snails Biomphalaria glabrata to PHMB induces changes in biometric and behavioral parameters, cellular immune responses, and mutagenicity. Snails were exposed to PHMB at 0.4, 0.6 and 0.8 mg L-1 for 120 h. Shell size and total weight of the snails were measured. Lethargy, shell reclusion, lateral tilt and hemolymph release behavior were evaluated. Hemocyte counts and frequencies of micronuclei, binucleated cells, and apoptotic cells were also assessed. PHMB had no effect on shell diameter or total weight of snails; however, PHMB at 0.8 mg L⁻¹ induced severe behavioral changes such as visceral mass exposure, hemolymph loss, and death within 24 hours. PHMB reduced the frequency of granulocyte hemocytes and increased the frequency of hyalinocytes at 0.8 mg L-1 and blast-like cells at 0.4 mg L-1. Mutagenic effects were observed in snails exposed to PHMB at 0.6 and 0.8 mg L⁻¹, with increased frequencies of micronuclei, binucleated cells and apoptotic cells. PHMB induced behavioral, immunotoxic, and mutagenic changes in B. glabrata, demonstrating its potential ecotoxicological impact to freshwater gastropods.