IN-VIVO AND IN-VITRO INITIATION OF SPERM MOTILITY USING FRESH AND CRYOPRESERVED GAMETES FROM THE PACIFIC HERRING, CLUPEA-PALLASI

Pacific herring (Clupea pallasi) gametes were cryopreserved in a simpl e extender (15% dimethyl sulfoxide in herring Ringers). Sperm remained viable for over 7 months when kept at liquid nitrogen temperature. A rapid cooling rate by directly plunging into liquid nitrogen allowed a majority of the cells to remain viable after subsequent thawing at 26 degrees C. Cryopreserved sperm initiated motility (activation) under both in vivo (in the micropyle area of the egg) or in vitro (in the pr esence of isolated sperm motility initiation factor or low sodium seaw ater) conditions. In addition to their ability to undergo activation, cryopreserved sperm were capable of fertilizing fresh eggs in a concen tration dependent manner resulting in > 90% fertilization and embryoni c development. Herring eggs cryopreserved in a similar manner as sperm remained intact in gross morphology. Although cryopreserved eggs were not fertilizable, both fresh and previously frozen sperm were activat ed in the micropyle areas of the chorions. The method we describe to c ryopreserve gametes from this species is simple and is useful for futu re experimental studies of sperm-chorion interaction when fresh materi al is unavailable. (C) 1994 Wiley-Liss, Inc.