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 ۲۰۱۰ ? ۲۰۰ ?w.cm-۲ in different times including ۰, ۱, ۳, ۵, ۸, ۱۰, ۱۵, ۲۰, ۲۵, ۳۵ and ۴۵ 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 ۰+ to ۳ min irradiation, but better hatching rates were observed at more prolonged irradiation times. The best hatching rate was achieved at ۲۵ min of UV irradiation; after that the survival rates rapidly declined to near zero. For PR studies, the semen was irradiated with UV (۵, ۳۰ and ۱۲۰s) and untreated semen (۰s) was used as control. Irradiated semen and/or fertilized eggs by treated semen were exposed to visible light (۶۰ W) at a distance of ۳۰ cm for ۱۰ min; the eyed and hatching rates were measured. UV irradiation as low dose as ۵s, significantly decreased the hatching rate (P <۰.۰۵). Semen and/or eggs illumination with visible light could not improve the survival rates (P >۰.۰۵). So, based on the results of this study, it was impossible to detect any PR mechanism in Caspian salmon.

Keywords:

Caspian Salmon , Salmo trutta caspius , Hertwig effect , Photoreactivation , Ultraviolet irradiation