Exposure to the Environmental Toxins Microcystin-LR and Roundup® Causes Cellular Damage in the Hepatopancreas of the White River Crayfish (Procambarus acutus)

Aquatic ecosystems are routinely exposed to natural and anthropogenic stressors, and when multiple pollutants co-occur, their synergistic effects may exceed those of individual contaminants. This study evaluated the individual and combined effects of the widely used agrochemical Roundup®, whose active ingredient is glyphosate (GLY) and the cyanobacterial toxin microcystin-LR (MC-LR) on the hepatopancreas of crayfish. Following a seven-day exposure to MC-LR (15 ppb), GLY (75 ppb), or their combination (MC-LR + GLY), cellular and morphological alterations were assessed using flow cytometry and histological analyses. MC-LR exposure increased hepatopancreatic vacuole number 3.7-fold and vacuole proportion 6.8-fold relative to controls, whereas GLY increased vacuole proportion 5.2-fold. Combined exposure increased tubule lumen proportion by approximately 65%, while epithelial height remained unchanged. GLY reduced viable (fluorescein diacetate-positive) hepatopancreatic cells by approximately 86%, and both GLY and MC-LR + GLY increased non-viable (propidium iodide-positive) cells by 4.8-fold and 4.3-fold, respectively. MC-LR alone did not significantly affect cell viability. These findings indicate that MC-LR primarily induces structural alterations, whereas GLY causes pronounced cellular cytotoxicity. Although co-exposure did not consistently produce synergistic toxicity, it enhanced tissue remodeling, emphasizing the importance of evaluating environmentally relevant contaminant mixtures and their implications for freshwater ecosystem health.