Histopathology of Carp (Cyprinus carpio L.) Larvae Exposed to Cyanobacteria Extract

Abstract

The aim of this study was to examine histological changes of tissues of carp embryos and larvae exposed for a short-term (8 days) or a long-term (30 days) to the crude extract of cyanobacteria with the cumulative concentration of 130.0 gl -1 (high concentration of the extract), 13.0 gl -1 (medium concentration of the extract) and 1.3 gl -1 (low concentration of the extract) of microcystins LR, RR and YR. The concentration of 130.0 gl -1 was used only for the short-term exposure. Tissue sections were stained with haematoxylin-eosin and PAS and examined using light microscopy. Apoptotic cells were detected by TUNEL test. Changes of liver and kidney, in particular, were examined. No histopathological changes were found in control or experimental groups after the short-term exposure except for non-resorbed yolk sacks in the group exposed to the high concentration of the extract. The development had been retarded in this group. Vacuolar dystrophy of hepatocytes accompanied by damage of nuclei (pyknosis, karyolysis) were found after the long-term exposure in the group exposed to the low concentration of the extract. Focal necroses and dystrophic changes of hepatocytes with vacuolization and nuclei damage (pyknosis, karyolysis, hyperchromatosis, karyorrhexis) were found in the group exposed to the medium concentration of the extract for a long term. Apoptotic cells were detected in the liver. No changes were found in the kidney. The results documented the damage of liver tissue in larval stages of carp exposed to the crude extract of cyanobacteria in early life stages of development. The degree of damage depended on the concentration of the extract.