Determination of lethal concentration and physiological responses of golden mussels (Limnoperna fortunei) exposed to the molluscicide MXD-100®

Since its introduction to Brazil in 1998, the golden mussel ( Limnoperna fortunei ) has caused significant ecological and economic impacts, demanding effective control strategies. The compound MXD-100, based on tannins and quaternary ammonium compounds (QACs), has shown promise in combating this invasive species. This study evaluated the acute toxicity of MXD-100 and its physiological effects on L. fortunei , being the first to investigate the mechanisms affected by this product. In 96-hour semi-static system tests, organisms were exposed to concentrations of 0.0025, 0.005, 0.010, 0.020, 0.060, 0.080, and 0.160 ppm. Concentrations ≥ 0.160 ppm caused 100% mortality within 48 h (LC₅₀ = 0.016 ppm). Survivors exhibited reduced levels of Cl⁻, Na⁺, Ca²⁺, Mg²⁺, and K⁺, along with changes in glucose and lactate. At sublethal exposure (0.003 ppm), reductions in water content, osmolality, ions, and glucose were observed, along with increased lactate and carbonic anhydrase activity, as well as damage to the digestive gland, including enlarged tubule lumens, epithelial cell atrophy, expanded interstitial space, necrotic areas, and epithelial vacuolization. The results demonstrate that MXD-100 not only prevents fouling but also triggers severe physiological imbalances, disrupting ion regulation, energy metabolism, and tissue integrity, ultimately leading to mortality. These findings represent an advance in understanding the product’s mode of action, highlighting its potential as a control agent for L. fortunei .