Histopathological Changes Induced by Chronic, Sub- Lethal Diazinon Exposure in Alligator Gar (Atractosteus Spatula) Tissues

Abstract

Diazinon is a widely used household and agricultural pesticide that accumulates in the aquatic environment and adversely affects non-target organisms such as mammals, birds, and fish. Sub-lethal pesticide levels occur in natural waters, and can impact the health, physiology and fitness of fish populations. This study was conducted to assess the effects of chronic, sub-lethal diazinon exposure to skin, liver, kidney, spleen, heart, gut, intestine, and gas bladder tissues of alligator gar, Atractosteus spatula. In two studies, gar were exposed to sub-lethal concentrations of 0.01, and 0.1 mg/L diazinon for 15 and 30 day periods. Skin, gills, liver, and kidney of exposed fish demonstrated remarkable microscopic lesions. These changes included skin lesions in the head and body, which started as white spots and progressed into deep ulcerations, hepatic vacuolation, swollen hepatocytes, steatosis, aggregation of macrophages, necrosis, and hepatic fibrosis. Gill tissues demonstrated epithelial hyperplasia in the secondary lamellae. Vacuolar degeneration was also present in the hematopoietic tissues of the kidney. Lesion occurrence and severity were correlated to increased diazinon dose and exposure time. Our findings revealed the harmful effects of chronic, sub-lethal diazinon exposure on alligator gar, and suggest other aquatic organisms may also be affected by sub-lethal concentrations of pollutants in their environment.