Preimplantation Development in Vivo and in Vitro in Bank Voles, Clethrionomys Glareolus, Treated With PMSG and HCG

Ovulation can be induced in the bank vole by PMSG and HCG and takes place 9 1/2 to 11 1/2 hr after administration of HCG. The number of eggs obtained varied from 1 to 30 (average 9.3). The highest ovulation rates were observed when PMSG and HCG were administered 41 to 43 1/2 hr apart. The embryos attained the blastocyst stage 96 hr after HCG injection. Bank vole eggs can be cultured in chemically defined media beginning with the eight-cell stage; only 25% of four-cell eggs developed to blastocysts in vitro.