Cryopreservation of Blue Catfish Spermatozoa and Subsequent Fertilization of Channel Catfish Eggs

Abstract

Successful cryopreservation of fish spermatozoa has important implications for genomic conservation and for aquaculture. We report the first long-term cryopreservation of ictalurid sperm. Spermatozoa from nine blue catfish Ictalurus furcatus were cryopreserved for 12 months in three concentrations (3.75 × 108, 1.50 × 109, and 6.00 × 109 spermatozoa per straw), within two different straw sizes (0.5 and 1.0 mL), and with two cryoprotectants (DMSO or methanol combined with powdered skim milk). Cryopreserved spermatozoa were then used to fertilize lots of 450 eggs of channel catfish Ictalurus punctatus. Mean relative fertilization percentage for sperm treated with DMSO was 32% (range of 23–54%) of the fresh control. Spermatozoa frozen with the combination of an intracellular cryoprotectant (methanol) and an extracellular cryoprotectant (skim milk) produced no fertilization. No difference (P > 0.05) was observed between fertilization percentage of spermatozoa frozen in the two straw sizes. The highest level of relative fertilization percentage (54%) was achieved with the highest insemination dose, 6.00 × 109 spermatozoa per straw (P < 0.05). There was no difference (P > 0.05) in fertilization percentage between insemination doses of 3.75 × 108 and 1.50 × 109 spermatozoa per straw. Cryopreservation of blue catfish spermatozoa can be optimized by using the high concentration of sperm (6.00 × 109) and DMSO as cryoprotectant in either 0.5- or 1.0-mL straws.