Cryopreservation of common carp (Cyprinus carpio L.) sperm I. The importance of oxygen supply

Experiments were carried out on the cryopreservation of common carp ( Cyprinus carpio L.) sperm. The effects of pre-freezing oxygen supply on post-thaw motility and the efficacy of different extenders were studied. Sperm diluents contained DMSO as a cryoprotectant in 10% final concentration. The dilution rate was 1:9 (sperm:diluent). Sperm was diluted and equilibrated (10 min) at 0°C. Sperm was then frozen in plastic straws (0.5 ml) at the following rate: 0°C–4°C: 4°C min⁻¹−4°C–80°C: 11°C min⁻¹ from −80°C, straws were plunged directly into liquid nitrogen (−196°C) for further storage. Frozen samples were thawed in a water bath at 40°C.
The freezability of common carp sperm showing reduced motility (due to suboptimal oxygen supply) after transportation could be restored when 30 min of oxygenation was applied prior to freezing. Highest post-thaw motility (57%, percent of control) was achieved when sperm was diluted with modified Kurokura's 'Extender 2'.