INVITRO FERTILIZATION OF LOBSTER OOCYTES

The feasibility of fertilizing preovulatory lobster oocytes was examined in vitro under various experimental conditions. Large (1.6 mm diameter) and small (0.6 mm diameter) oocytes were compared in fertilization trials. Small oocytes were surrounded by a thin envelope thought to correspond to envelope 1A of mature oocytes. Large oocytes were surrounded by a fully formed vitelline envelope comprised of two distinct sublayers, 1A and 1B. Although sperm bound very effectively to the coat surrounding small oocytes, none penetrated the coat or fertilized the oocytes. Large diameter oocytes that were removed from follicles by dissection were fertilized by sperm from the proximal vas deferens of males and by sperm from the seminal receptacle of females. Fertilized oocytes showed a high degree of polyspermy. Higher numbers of sperm bound to, penetrated, and fertilized large diameter oocytes when inseminations were done in a saline solution (2.5LSH) than when done in artificial sea water (ASW). Sperm failed to bind to large diameter oocytes that were induced to ovulate in vitro by collagenase treatment. Contaminating enzymes may have destroyed the sperm receptor in envelope 1A of collagenase treated oocytes. Our in vitro fertilization method will allow the process of fertilization to be studied experimentally in lobsters, and it may be applicable to other decapods.