Morphological, biochemical, and histological alterations in juvenile giant freshwater prawns (Macrobrachium rosenbergii) exposed to sub-lethal concentrations of 2,4-D dimethylammonium

Abstract

The widespread use of herbicides, such as 2,4-D dimethylammonium, poses significant risks to aquatic ecosystems. This study assessed the toxicological effects of 2,4-D dimethylammonium on juvenile giant freshwater prawns (Macrobrachium rosenbergii) by assessing mortality, total hemocyte count (THC), acetylcholinesterase (AChE) expression, and tissue integrity using optical coherence tomography (OCT) and histological analysis. Prawns were exposed to 0, 250, 300, 350, 400, and 450 μL/L of 2,4-D dimethylammonium for 24, 48, 72, and 96 h, and both LC₅₀ values and sub-lethal effects were examined. Acute toxicity tests revealed dose- and time-dependent mortality, with declining LC₅₀ values over 24 to 96 h. THC levels significantly decreased (p < 0.05) at higher concentrations, with prawns exposed to 450 μL/L showing a 35 % reduction at 96 h. Western blot analysis revealed AChE suppression, with expression becoming faintly detectable at 72 h and undetectable at 96 h at 450 μL/L. OCT analysis showed tissue disorganization, increased light scattering, and structural degradation, aligning with histological findings of hepatopancreas and muscle deterioration in high-exposure groups. The study highlights the environmental risks of 2,4-D dimethylammonium contamination and supports OCT as a non-invasive tool for assessing pesticide toxicity in aquatic organisms.