Developmental capacity of Antarctic minke whale (Balaenoptera bonaerensis) vitrified oocytes following in vitro maturation, and parthenogenetic activation or intracytoplasmic sperm injection

The present study investigated the effects of the sexual maturity of oocyte donors on in vitro maturation (IVM) and the parthenogenetic developmental capacity of fresh minke whale oocytes. The effects of cytochalasin B (CB) pretreatment and two types of cryoprotectant solutions (ethylene glycol (EG) or ethylene glycol and dimethylsulfoxide (EG + DMSO)) on the in vitro maturation of vitrified immature whale oocytes were compared, and the developmental capacity of vitrified immature whale oocytes following IVM and intracytoplasmic sperm injection examined (ICSI). The maturation rate did not differ significantly with sexual maturity (adult, 60.9%; prepubertal, 53.1%), but the parthenogenetic activation rate of oocytes from adult donors (76.7%) was significantly higher (p < 0.05) than that of oocytes from prepubertal donors (46.4%). The maturation rates after vitrification and warming were not significantly different between the EG (22.2%) and EG + DMSO groups (30.2%), or between the CB-treated (30.4%) and non-CB-treated groups (27.3%). These results indicate that parthenogenetic activation of in vitro matured oocytes from adult minke whales was superior to that from prepubertal whales, but that the developmental capacity of the whale oocytes after parthenogenetic activation or ICSI was still low. The present study also showed that CB treatment before vitrification and two kinds of cryoprotectants did not improve the IVM rate following the vitrification of immature whale oocytes.