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The present study was conducted to evaluate the effects of vaccination against furunculosis on responses of oxidative stress and antioxidant defenses in rainbow trout Oncorhynchus mykiss muscle, gills, liver, and brain tissues. The oxidative stress markers (malondialdehyde and carbonyl derivatives of protein oxidative destruction levels), antioxidant defenses (superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase), and total antioxidant capacity in different tissues of rainbow trout were measured. Our data showed that exposure of trout to vaccine against furunculosis produced changes (either increase or decrease) in oxidative stress and antioxidant enzymes responses, and these responses showed marked organ differences, associated with tissue patterns. Our study demonstrated that vaccinated trout showed alteration in antioxidant defenses and oxidative stress responses, with higher severity in the liver, compared with other tissues. Our data also suggest that vaccination against furunculosis induced lipid peroxidation in gill and liver tissues. However, muscle and brain tissue are capable of restoring its pro- and antioxidant balance after vaccination.

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In this study we investigated the effect of pH (range 5.5-10.5) on sperm motility of rainbow trout (Oncorhynchus mykiss) and other fish species from family Salmonidae: brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), Atlantic salmon (Salmo salar), and grayling (Thymallus thymallus). Video recordings of sperm motility were analyzed using Hobson Sperm Tracker. Since urine contamination of milt was suspected to modulate motility, the effect of pH on rainbow trout spermatozoa was re-evaluated with the use of semen collected with a catheter. Spermatozoa of all the species except for rainbow trout were characterized by a broad pH range for the motility. At a pH of 5.5, motile sperm was observed for both brook trout and brown trout, 31 and 38%, respectively. For rainbow trout spermatozoa collected by stripping, no motility was observed at pH 7.0 and below. On the contrary, when sperm from rainbow trout was collected using a catheter we observed motility at low pH values. Our results demonstrated that salmonid spermatozoa can be motile in a wide range of pH values, including the acidic range. Our results suggest that urine contamination significantly affects pH-dependence of sperm motility activation in fish.