In vitro fertilization and embryo development in the marmoset monkey (Callithrix jacchus).

Oocytes aspirated from preovulatory (i.e. > or = 2 mm) follicles of marmoset monkeys were graded for maturity according to the degree of cumulus expansion, grade I being most mature and grade IV least mature. After preincubation for 2-5, 9-11 or 21-29 h, 82% of oocytes could be fertilized using epididymal spermatozoa and only 2.3% were polyspermic. Fertilization rate was lowest (60%) in grade IV oocytes and all oocytes preincubated for 2-5 h (53%). Fertilization rate increased to 92% in oocytes preincubated for 21-29 h. Embryos developed in vitro to a mean of eight cells. Embryo development was unaffected by oocyte maturity but correlated with preincubation time. Oocytes preincubated for 2-5 h developed into embryos with significantly fewer cells than those preincubated for 9-11 or 21-29 h (P < 0.001). Fifty-six per cent of embryos showed delayed cleavage and these had fewer cells than non-delayed embryos (P < 0.001). When oocytes were preincubated for 2-5 h, development of all resulting embryos was delayed. However, only 17 and 58% of embryos developing from oocytes preincubated for 9-11 and 21-29 h, respectively, were delayed and this was independent of oocyte maturity.