Abstract
Freshwater pollution is one of the major issues in South Africa. Roodeplaat Dam located north-east of Pretoria, is a highly polluted impoundment affected by anthropogenic impacts. The health of fish inhabiting the system is adversely affected by pollution. Results from previous studies reported various histological alterations in the liver of Clarias gariepinus (Burchell 1822) where tissues were sampled using lethal techniques. Previous non-lethal studies performed on fish reported success in accurately identifying pathology in target species. Currently, there is no literature on the use of image-guided non-lethal sampling techniques for histological analyses in C. gariepinus. The current study aimed to test the efficacy of an image-guided non-lethal needle biopsy technique to assess the liver of C. gariepinus. A total of 20 C. gariepinus were sampled from the Roodeplaat Dam and non-lethal needle liver biopsies were performed under ultrasound guidance. Following the biopsies, 5 of the fish were placed in active biomonitoring containers exposed to dam water and monitored to assess the impact, if any, that the polluted water of the system might have had on the needle entry site. Blood was collected and standard terminal sampling was done on all 20 fish to collect liver samples for comparison with the biopsied tissue. Skin samples were also collected for histological assessment to identify any signs of inflammation at the needle entry site. Tissue samples from both techniques were processed for light microscopy and stained with Haematoxylin and Eosin. The ultrasound was successful in identifying the liver tissue and adequate tissue samples were obtained for histological analysis using this technique. Histological assessments showed intact tissue structure with clear cellular detail in the biopsy samples. All functional units of the liver were identifiable and were comparable to those observed in terminally collected samples. Similar histological alterations such as hypertrophy of the hepatocytes, steatosis, and nuclear pleomorphism were identified in both groups. Histological assessments of the liver and skin tissue samples showed no signs of inflammation at the needle entry site. Differential white blood cell count showed a varying trend of white blood cells after monitoring. The findings of this study suggest that the non-lethal sampling technique was successful for histological analyses and no adverse reactions were observed on the needle entry site after active monitoring.
Keywords: Clarias gariepinus, Roodeplaat Dam, Histology, Liver, Non-lethal sampling techniques