Cryopreservation of Mesopotamian catfish (Silurus triostegus H., ۱۸۴۳) spermatozoa: Effects of diluents and osmotic pressure on spermatozoa DNA damage, rate and duration of motility

This study was performed to evaluate the effectiveness of three different conditions of osmotic pressure (۳۲۵, ۳۶۵ and ۳۸۵ mOsm kg-۱) in combination with dimethyl sulfoxide (DMSO) and NaCl or glucose on spermatozoa DNA damage, rate and duration of motility. Sperm was collected from eight healthy mature Mesopotamian catfish, evaluated microscopically and pooled at ۲۵ °C. The pooled sperm samples were diluted to a final concentration of ۱/۳ (sperm/diluents) in  NaCl and glucose based extender (۱۰% cryoprotectant and ۱۰% egg yolk (EY) into ۸۰% diluents) and separated into groups of ۳ different osmotic pressures (۳۲۵-۳۶۵-۳۸۵ mOsm kg-۱). Equilibrated sperm was frozen in ۰.۲۵ mL straws. Sperm samples were tested for post-thaw sperm motility, duration of motility, DNA damage, and apoptotic index. The highest spermatozoa motility rates were obtained with glucose and NaCl diluents at osmotic pressures of ۳۶۵ and ۳۸۵ mOsm kg-۱ (p<۰.۰۱). The spermatozoa motility duration was found to be the highest in glucose and NaCl diluents at ۳۶۵ mOsm kg-۱ osmotic pressure (p<۰.۰۱). The post-thawing live spermatozoa rate was determined to be the highest in the sperm frozen with glucose at ۳۸۵ mOsm kg-۱. The apoptotic cell rate was determined to be the highest in the sperm frozen with glucose at ۳۸۵ mOsm kg-۱ osmotic pressure. The necrotic cell rate was found to be the highest with ۲.۰۸±۰.۳۹% when frozen with the glucose diluent at ۳۲۵ mOsm kg-۱ pressures. It is concluded that the glucose solution with low osmolality had a harmful effect on the spermatozoa.

Keywords:

Silurus triostegus , Cryopreservation , DNA damage , Osmotic pressure