Life-stage-resolved toxicological assessment and environmental relevance of triclosan in the freshwater gastropod Biomphalaria glabrata.

Abstract

TCS (triclosan) is frequently detected in freshwater compartments, including surface water, sediments, biosolids, and pore water; however, its life-stage-specific toxicity in gastropod mollusks remains insufficiently characterized. To address this gap, this study aimed to determine the life-stage-dependent lethal and sublethal toxicity of TCS in Biomphalaria glabrata and identify environmentally relevant endpoints for gastropod ecotoxicology and life-stage-aware ecotoxicological assessment. We applied a life-stage-resolved framework covering embryonic development, newly hatched juveniles, acute adults, and chronic adults, assessing survival, developmental abnormalities, adult behavior, hemolymph label-free 3D imaging, AChE (acetylcholinesterase)/SOD (superoxide dismutase) activities, growth, reproduction, and histopathology. Embryos were most sensitive, with a 216 h LC₅₀ (median lethal concentration) of 0.1672 mg/L, edema at ≥ 0.20 mg/L, and blastula arrest at ≥ 0.25 mg/L. Newly hatched juveniles showed intermediate acute sensitivity (96 h LC₅₀ = 0.5818 mg/L), whereas adults were less sensitive to acute lethality (96 h LC₅₀ = 2.552 mg/L) but showed reduced escape, prolonged retraction, and visible hemocyte structural injury at ≥ 2.0 mg/L. Concentration-response modeling of the Day 21 endpoints yielded model-derived EC₅₀ (Effect Concentration) values of 0.0674 mg/L for relative body-mass change, 0.1153 mg/L for shell growth, and 0.2276 mg/L for cumulative egg-mass production. These response patterns indicate that somatic growth endpoints were more consistently responsive than reproductive output under the present experimental conditions. Overall, TCS induced stage-dependent lethal and sublethal toxicity in B. glabrata, highlighting the importance of considering the particularly sensitive embryonic stage in life-stage-aware ecological hazard assessment.