Cryopreservation effects on the sperm quality of cachama blanca Piaractus brachypomus (Cuvier 1818)

The effects of straws volume, cryoprotectants and thawing temperatures were evaluated on the sperm quality of cachama blanca Piaractus brachypomus (Cuvier), an important Colombian fish species. Sexually mature fish were induced to ovulation or spermiation with a carp pituitary extract. A pool of suitable sperm samples was diluted in glucose, egg yolk, dimethyl sulphoxide (DMSO-10%), methanol (MET-10%) or ethylene glycol (ETG-5%) and packed in 0.5, 2.5 or 5.0 mL straws and frozen in nitrogen vapour. The thawing process was performed in a 35 or an 80 degrees C water bath. The fertility was evaluated after 6 h post fertilization. The highest motility percentage (33 +/- 3%) was observed with sperm cryopreserved with DMSO, packed in 5 mL straws and thawed at 35 degrees C. The treatments with DMSO and MET packed in 0.5 and 5.0 mL straws and thawed at 35 degrees C showed the highest fertility (higher than 71%) and the lowest fertility was obtained with MET-2.5 mL (9 +/- 5%). In all the treatments, a significant decrease in the sperm quality was observed at 80 degrees C. Sperm cryopreserved with DMSO-10% or MET-10%, packed in 2.5 or 5.0 mL straws are suitable to achieve acceptable fertilization and to fertilize high amounts of eggs.