Cellular stress response, induction of micronuclei and DNA strand breaks in two common fish species of Rivers and Reservoirs in Ilorin, North Central, Nigeria.

Most rivers and reservoirs in the world are prone to pollution because of indiscriminate disposal of domestic, agricultural and industrial wastes into the water bodies. In this study, we investigated the ecotoxicological potential this could pose in fish species collected from major reservoirs and rivers in Ilorin, north central, Nigeria. Water samples were collected and the physicochemical parameters were examined from five different sites; Unilorin reservoir, Asa reservoir, Apodu reservoir, Asa river (Unity) and Asa river (Harmony). We determined serum biochemical (AST, ALT, ALP, serum ALB), histopathological (gill, lungs), serum antioxidant enzyme responses (SOD, CAT, GPx, GR, GST) which serves as a biomarker for evaluating oxidative stress while micronucleus and comet assays were used to detect level of DNA damage in Tilapia zillii and Clarias gariepinus. The physicochemical parameters and heavy metal analysed (Pb, Mn, Cu, Ni, N, P, Fe, Cl, and Ca) in the five different water bodies were below the permissible limits of WHO and USEPA except the DO, which was very low in the two rivers, indicating hypoxia. Our results showed significant increase in biochemical and hematological profiles, histopathological lesions in the gill and lungs, inductions of MN, NA and DNA single strand break in Tilapia zillii and Clarias gariepinus collected from Asa rivers compared to the Unilorin, Apodun and Asa reservoirs. This may be attributed to indiscriminate discharge of effluents from nearby industries, agricultural and domestic wastes into the rivers.

Helminth parasites of cultured Clarias gariepinus and Tilapia zillii in Uyo, Akwa Ibom State, Nigeria

The study examined helminth parasites of cultured Clarias gariepinus and Tilapia zillii in Uyo, Akwa Ibom State. A total of 60 fish samples (30 each of C.gariepinus and T. zillii) were subjected to parasitological examinations. Results revealed a total of 47(78.33%) fishes infected with various species of parasites: Nematodes (Camallanus polypteri, Paracamallanus cyathopharynx, and Procamallanus laevionchus), Cestodes (Polyonchobothrium torulosus and P. clariae) and Trematodes (Dactylogyrus extensus and Glossiduim pedatum) in decreasing order of abundance. Out of the 60 fish samples examined, 47 were infected with 219 parasites: 142(64.84%) nematodes, 40(18.26%) cestodes and 37(16.89%) trematodes. A total of 159(72.60%) parasites were recovered from C. gariepinus out of which 103(64.78%) were nematodes, 19(18.45%) were cestodes and 37(35.92%) were trematodes. While 60(27.40%) parasites were recovered from T. zilli, of which 39(65.00%) were nematodes and 21(35.00%) cestodes. No trematode was observed in the tilapia. The overall prevalence of parasitic infection was 78.33%. The results of chi square analysis showed that females of both species had significantly higher (P<0.05) prevalence of infection 27(84.4%) than males 20(71.4%). Also, C. gariepinus had higher infection rate of 25(83.33%) when compared to 22(73.33%) recorded in T. zillii. Key words: fish parasites, aquaculture, prevalence, C. gariepinus, T. zillii

Accumulation of heavy metals in tilapia fish species and related histopathological changes in muscles, gills and liver of Oreochromis niloticus occurring in the area of Qahr El-Bahr, Lake Al-Manzalah, Egypt

Accumulation of metals (Fe, Zn, Cu, Mn, Pb, Cd and Ni) in the muscles and gills of Oreochromis niloticus, Oreochromis aureus and Tilapia zillii was assessed based on seven locations in the Qahr El-Bahr area in Lake Al-Manzalah. The average accumulation of metals was in the following order: Tilapia zillii > Oreochromis aureus > Oreochromis niloticus. To determine the risk of fish consumption, the estimated daily intake, carcinogenic, non-carcinogenic and relative risk indices were calculated. The results indicate that the intake of individual metals through the consumption of fish is almost safe for human health, whereas the intake of combined metals poses a high potential health risk to consumers. Assessment of carcinogenic risk of Cd and Ni from the consumption of tilapia species indicates that consumers are at risk of cancer. The contribution of Pb and Cd to the overall relative risk index ranged from 34% to 41%. Of the three species studied, Oreochromis niloticus is relatively safe for consumption as it poses the least health hazard, while Tilapia zillii is more predisposed to accumulate metals in its tissues. Histopathological changes were observed in the muscles, gills and liver of Oreochromis niloticus as a result of heavy metal accumulation in these organs.

Scanning morphology, prevalence and histopathology of some acanthocephalans infecting some River Nile fish

Acanthocephalan morphology and their adverse pathological impact on fish are of great concern. Two species of acanthocephalans were recorded from 800 samples of live freshwater fish collected randomly during 2017–2018 from Lake Nasser, Aswan, Egypt. The recovered species were identified morphologically as Acanthogyrus (Acanthosentis) tilapiae from three Tilapia spp. (Sarotherodon galilaeus, Oreochromis niloticus and Tilapia zillii) and Rhadinorhynchus niloticus from Lates niloticus. The intensity of parasitic infection and the seasonal prevalence were higher in L. niloticus than in Tilapia spp. The clinical signs and post mortem lesions of infected fish were reported. Morphological description of the detected parasites using light microscope was then confirmed by electron microscopy to amplify ambiguous details. The histopathological findings of the intestine of naturally infected fish with acanthocephalan parasites were investigated and described. The main damage caused by them is destruction of the mucosal epithelium of the villi, necrosis and degeneration of intestinal epithelial cells.