Semen cryopreservation of yellow croaker Larimichthys polyactis

Abstract

The effects of various extenders and cryoprotectants on movable spermatozoa ratio (MSR), spermatozoa velocity (SV) and duration of spermatozoa motility (DSM) of post-thawed spermatozoa were examined. The MSR, SV and DSM of post-thawed sperm in artificial seminal plasma (ASP) extender were higher than those in marine fish Ringer’s solution (MFRS) extender (P < 0.01) and was not significantly different from that of fresh sperm. No significant differences were observed in the motility parameters between fresh spermatozoa and frozen-thawed spermatozoa cryopreserved with ASP extender supplement 10% EG (ethylene glycol) cryoprotectant. Using the above method, yellow croaker semen was cryopreserved with extender ASP and 10% EG. As a result, at the spermatozoa/egg ratio of 100,000:1, the fertilization rate and hatching rate of the frozen-thawed spermatozoa cryopreserved for 1 week or 1 year in liquid nitrogen (45.7 ± 3.2% and 27.2 ± 5.0% or 37.5 ± 4.4% and 27.2 ± 5.0%) were similar to that of fresh spermatozoa (51.0 ± 3.1% and 36.7 ± 2.2%). There was a small alternation of shape in cryopreserved spermatozoa compared with fresh spermatozoa. In conclusion, the optimal conditions for yellow croaker semen cryopreservation are ASP extender supplement 10% EG cryoprotectant. This is the first report on semen cryopreservation of yellow croaker Larimichthys polyactis.