Histopathological Effects in Poecilia reticulata (Guppy) Exposed to Methyl Mercury Chloride

To evaluate the usefulness of histopathology in aquatic toxicity testing, studies were carried out on the small freshwater fish Poecilia reticulata (guppy) following aqueous methyl mercury chloride exposure. Fish were exposed to concentrations of 0, 1.0, 1.8, 3.2, 5.6, or 10 μg/L for 1 and 3 months. Histopathological changes included the occurrence of multiple granulomas in various tissues, in particular, the integument and orbit. These changes were accompanied by hyperplasia of monocytopoietic interrenal tissue, and hepatocellular change which was confirmed by morphometry. The latter findings were probably a result of monocyte "consumption" by granulomas, and hepatic synthesis of ("stress") proteins, respectively. The bile duct and, focally, the proximal intestine, showed hyperplasia of the epithelium. In the testis of sexually mature fish (3-month study), degeneration and necrosis of sperm occurred, with severe cases exhibiting Sertoli cell hypertrophy, interstitial inflammation, and absence of mature s...