In vitro maturation of whitefish, Coregonus lavaretus (L.), oocytes

Ovarian fragments of whitefish, Coregonus lavaretus (L.), were incubated in medium 199 with Earle’s salts at 10°C in the presence of 17alpha-hydroxy-20beta-hydroxyprogesterone (1 µg ml–1) or salmon pituitary extract (10 µg ml–1) for 5 or 10 days. These hormones induced both cytoplasmic and nuclear maturation of 91–100% of oocytes within 3–4 days. However, ovulation in vitro was observed only from follicles stimulated to mature in vivo. Fusion of oil droplets in vitro was usually incomplete as compared with in vivo maturation.