Cryopreservation and short-term storage of sturgeon sperm, a review

Sturgeon sperm was cryopreserved in liquid nitrogen or stored at 1-4 degreesC on a short-term basis. The objective was to establish reliable technologies for the conservation of certain endangered sturgeon species and for artificial reproduction in sturgeon farms. Cryopreseved sperm was diluted in buffered extenders (pH between 8 and 8.5) containing intracellular (dimethyl-sulfoxide (DMSO), methanol, ethylene glycol) or extracellular (saccharose, egg yolk) cryoprotectants. The concentration of intracellular cryoprotectants ranged from 5% to 20%. Tested freezing rates were in a range of 0.5-18.5 degreesC/min and the thawing rate between 15 and 40 degreesC/min for 5 to 6 s. Ten to eight percent of the sperm were motile after thawing. Fertilization rates up to 73-94% were reported for thawed sperm but in most cases, average values were 20%. The motility of non-frozen sperm was activated after few days of in vitro storage. Motility declined with time depending on oxygen availability in the milt, temperature (optimum near 0 degreesC) and pH; though some spermatozoa were still motile after several weeks of storage. (C) 2004 Published by Elsevier B.V.