Histopathology and micronuclei induction as pollution biomarkers in common carp, Cyprinus carpio from southern Iraq

This study aimed to assess the histopathological alterations and micronuclei induction in the gill, kidney and liver of common carp, Cyprinus carpio from Al-Huwaizah Marshes, Al-Hammar Marshes and Al-Sweap River. Thirty C. carpio were sampled at each locality using monofilament gillnets. Most prominent histopathological alterations recorded in the gill included formation venous sinus in primary lamellae, oedema, curling and distortion of primary lamellae fusion of secondary lamellae, hyperplasia of epithelial cells, necrosis, curling of secondary lamellae, severe dilation of lamellar capillaries, clavate lamellae formation at the tip of secondary lamellae, a proliferation of cartilage tissue in primary lamellae and lifting of the lamellar epithelium whereas congestion, fibrosis with proliferative inflammation, necrosis area, degenerated cells, vacuolar degeneration, vacuolation, nuclear pyknosis, hypertrophy of hepatocytes were reported in the liver. In the kidney, the most pronounced changes were necrosis of the hematopoietic tissue, hyaline droplet and activation of melanomacrophage centres. A higher prevalence of alterations was observed in the population from Al-Huwaizah Marshes, however, Al-Hammar population exhibited severe pathologies. Micronuclei frequency was significantly higher at Al-Huwaizah Marsh (p < 0.05) with low frequency being recorded at Al-Sweap River. This study attests to the effectiveness of histopathology and micronucleus induction as potential tools for discriminating the health of populations from different water bodies.