Fertilization in landlocked sea lamprey: storage of gametes, optimal sperm: egg ratio, and methods of assessing fertilization success

Ovulated, unfertilized eggs of sea lamprey Petromyzon marinus could be stor ed for 1 day at 15 degrees C without significant loss of fertilizing abilit y. After 2 days storage most eggs could still be fertilized. Lamprey semen could be stored up to 1 day. Thereafter, a decrease in sperm fertilizing ab ility occurred, accompanied with a decrease in sperm motility. Unlike teleo st fish, sea lamprey eggs could still be fertilized after 1 h contact with water. This extended time of gamete fertility after release into water may help to account for the reproductive success of this species. Maximal ferti lization rates were obtained at a sperm:egg ratio of 50 000, a ratio recomm ended for studies on fertility of individual males. Assessing fertilization success 3 min after fertilization (at cytoplasmic bleb stage) or 5 h after fertilization (at two-cell embryo) was strongly correlated (r=0.92 and 0.9 8) with estimation and Fertilization success at hatching. These results off er improvement in artificial fertilization techniques under laboratory cond itions and provide new information on the biology of fertilization in sea l amprey. (C) 2000 The fisheries Society of the British Isles.