Sperm fertilization capacity of Caspian salmon, Salmo trutta caspius under ultraviolet irradiation

The optimum dose of ultraviolet (UV) irradiation to produce gynogenetic Caspian salmon, Salmo trutta caspius, with emphasis on the "Hertwig effect" and photoreactivation (PR) were investigated. The sperm of Caspian salmon was irradiated with UV at 2010 ? 200 ?w.cm-2 in different times including 0, 1, 3, 5, 8, 10, 15, 20, 25, 35 and 45 min and was allowed to fertilize normal ova; the fertilization, eyed and hatching rates were calculated to assess the performance. Using the irradiated sperm decreased the fertilization, eyed as well as hatching rates and the so-called "Hertwig effect" was observed, with the time-dependent decrease in the hatching rates at 0+ to 3 min irradiation, but better hatching rates were observed at more prolonged irradiation times. The best hatching rate was achieved at 25 min of UV irradiation; after that the survival rates rapidly declined to near zero. For PR studies, the semen was irradiated with UV (5, 30 and 120s) and untreated semen (0s) was used as control. Irradiated semen and/or fertilized eggs by treated semen were exposed to visible light (60 W) at a distance of 30 cm for 10 min; the eyed and hatching rates were measured. UV irradiation as low dose as 5s, significantly decreased the hatching rate (P 0.05). So, based on the results of this study, it was impossible to detect any PR mechanism in Caspian salmon.