Comprehensive evaluation of 2,4-D dimethylammonium toxicity in rice field crabs (Somanniathelphusa bangkokensis)

2,4-D dimethylammonium is a widely used herbicide known for its environmental persistence and adverse effects on aquatic ecosystems. This study investigates the toxicological impacts of 2,4-D dimethylammonium on rice field crabs (Somanniathelphusa bangkokensis), focusing on morphological, biochemical, and histological alterations. Crabs were exposed to varying concentrations of 2,4-D dimethylammonium (210–378 mg/L) for 24, 48, 72, and 96 h. Optical coherence tomography (OCT) revealed significant structural damage in the gills, including tissue swelling, lamellar collapse, and cuticle rupture, and in hepatopancreas tissues, including vacuolation and lumen distension. Hemocyte analysis showed a reduction in total hemocyte count and abnormal cell morphology, indicating impaired immune function. Biochemical assays revealed a dose- and time-dependent inhibition of acetylcholinesterase (AChE) activity, with SDS-PAGE and Western blotting confirming AChE expression at 71 kDa. Histological analysis supported these findings, with progressive tissue damage correlating with both herbicide concentration and exposure duration. The study highlights the systemic effects of 2,4-D dimethylammonium on rice field crabs, emphasizing the need for stricter herbicide regulation and further research into its long-term ecological impacts.