Histopatological alterations and oxidative stress in liver and kidney of Leuciscus cephalus following exposure to heavy metals in the Tur River, North Western Romania

Pollution of the aquatic environment by heavy metals is a great concern worldwide. Freshwater fish ingests various metals through gills, skin or diet. Our aim was to investigate the oxidative stress and histopathological injuries induced by Fe, Cu, Zn, Pb, Cd in the liver and kidney of Leuciscus cephalus. Fish samples were collected from two sites in the Tur River, NW Romania, in upstream and downstream of a pollution source. Metals were differently distributed in the liver and kidney of fish. The highest concentrations of Fe, Cu and Pb were found in liver, whereas Zn and Cd concentrations were the highest in kidney in specimens collected from the downstream site. The histopathological changes were associated with metal bioaccumulation, being more severe in kidney than liver. Malondialdehyde (MDA) and advanced oxidation protein products (AOPP) increased significantly in the liver and kidney of fish from downstream site compared to upstream one, whereas reduced glutathione (GSH) decreased. The activities of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST) increased significantly in livers, whereas SOD increased in kidney. Our study revealed that liver has a higher capacity and adaptability to counteract ROS compared to kidney. The more pronounced increase of hepatic SOD, CAT and GST activities is related milder structural changes observed in liver compared to kidney, where lesions were not reduced by antioxidant defense system.

Pathophysiology of Ichthyophthirius multifiliis infection in rainbow trout (oncorhynchus mykiss) and chub (Leuciscus cephalus)

The present study investigated the effect of experimental infection with Ichthyophthirius multifiliis on physiological, immunological and metabolic parameters in rainbow trout (Oncorhynchus mykiss) and chub (Leuciscus cephalus). Both species developed an immune response against I. multifiliis that was detected in the peripheral blood (i.e. increase in immunoglobulin concentrations in rainbow trout, increase in lymphocyte and thrombocyte concentrations in chub), but not in the skin mucus. Anaemia was observed in both species of fish. In rainbow trout there was also depletion of liver glycogen, disturbance in osmoregulation (decrease in serum osmolality and Na(+) and Cl(-) concentrations) and possibly also impaired wound healing capacity (i.e. decrease in skin mucus alkaline phosphatase and β-glucuronidase activity). Therefore, rainbow trout develop more severe changes following this infection compared with chub.

Precision of the age-length increments of three cyprinids: effects of fish number and sub-sampling strategy

The effects of number of fish that are aged and scale sub-sampling strategies on the precision of estimates of mean age-length increments from populations of Rutilus rutilus, Leuciscus leuciscus and Leuciscus cephalus were tested. Analyses used data derived from river fish communities in eastern England, U.K.. Regarding the number of fishes analysed in each age group, for each species and mean fork-length increment at age, significant relationships were detected between sample size (n) and the coefficient of variation of the mean (Z) and mean length increment x‾ and measured variance (s(2)). This enabled calculation of the number of scales for producing a mean length increment at age according to n=ax‾(b(-2))Zx‾(-2). Outputs indicated that the number of scales requiring ageing increased substantially as precision increased, but with little variation between species per age category. Ageing between seven and 12 scales per age group would thus provide estimates at 10% precision. As the ages of fishes are not known in advance of scale ageing, the effect of scale sub-sampling regime on precision was also tested using randomized strategies of 10 fish per 5 mm, five per 5 mm, three per 5 mm, 10 per 10 mm, five per 10 mm and three per 10 mm. These were applied to the datasets and the consequences of their reduction in the number of scales for precision were determined using Z=a(0.5)x‾((b/2)(-1))n(-0.5). When compared to no sub-sampling, three per 10 mm always significantly reduced data precision, whereas 10 per 5 mm never significantly reduced precision. These outputs can thus be applied to the design of fish sampling protocols where age and growth estimates are required, with the randomized sub-sampling likely to be the most useful strategy.