ROLE OF THE GAMETE MEMBRANES IN FERTILIZATION IN SACCOGLOSSUS KOWALEVSKII (ENTEROPNEUSTA)

Abstract

An earlier paper showed that in Saccoglossus the acrosomal tubule makes contact with the egg plasma membrane. The present paper includes evidence that the sperm and egg plasma membranes fuse to establish the single continuous zygote membrane which, consequently, is a mosaic. Contrary to the general hypothesis of Tyler, pinocytosis or phagocytosis plays no role in zygote formation. Contact between the gametes is actually between two newly exposed surfaces: in the spermatozoon, the surface was formerly the interior of the acrosomal vesicle; in the egg, it was membrane previously covered by the egg envelopes. The concept that all the events of fertilization are mediated by a fertilizin-antifertilizin reaction seems an oversimplification of events actually observed: rather, the evidence indicates that a series of specific biochemical interactions probably would be involved. Gamete membrane fusion permits sperm periacrosomal material to meet the egg cytoplasm; if an activating substance exists in the spermatozoon it probably is periacrosomal rather than acrosomal in origin. The contents of the acrosome are expended in the process of delivering the sperm plasma membrane to the egg plasma membrane. After these membranes coalesce, the sperm nucleus and other internal sperm structures move into the egg cytoplasm.

Biology of the Swimming Acorn WormGlandiceps hacksifrom the Seto Inland Sea of Japan

“…3. Inducing a change to seawater temperature has been a useful method for inducing artificial spawning in other acorn worms (Colwin and Colwin, 1962;Tagawa et al, 1998;Urata and Yamaguchi, 2004;Miyamoto and Saito, 2007). However, it is still unclear what triggers the induction of spawning in nature.…”

Linkage Analysis Using Somatic Cell Hybrids

“…Littlefield has estimated the frequency of viable hybrid formation at 1-5 x I0-6 • 115 Exceptions occur. Myoblasts 224 and gametes 36 undergo membrane fusion normally during their ontogeny. The cytopathology of virus infections in some instances involves membrane fusion, resulting in the formation of giant multinucleate cells (cf.…”