In new research that could have implications for improving fertilization in humans and other mammals, life scientists studied interactions between individual sperm and eggs in red abalone, an ocean-dwelling snail, and made precise chemical measurements and physical models of these interactions. They are the first scientists to do so.
By simulating the natural habitat of the abalone in the laboratory, the scientists were able to determine the conditions under which spermegg encounters and fertilization were most likely to occur.
"If we can understand the basic physics, chemistry and biology of reproduction, then moving from one species to the next is like dotting I's and crossing T's," said the study's lead author, Richard Zimmer, a UCLA distinguished professor of ecology and evolutionary biology.
Red abalone live in ocean crevices and spawn year-round, with females releasing several million eggs and males releasing up to 10 billion sperm directly into the ocean, Zimmer said.
In 2002, Zimmer's research team identified a molecule called tryptophan that is released by female abalone eggs to attract sperm. Now Zimmer and Jeffrey Riffell, an assistant professor of biology at the University of Washington, report that the released tryptophan creates a plume around the egg, greatly enlarging the target area for sperm, in much the same way using a larger tennis racket increases the chances of hitting the ball. The plume increases the egg size by a factor of five, the researchers said.
In addition, the egg has to release very little tryptophan to increase its target area, Zimmer and Riffell report in the journal Proceedings of the National Academy of Sciences. The research is currently online and will be in published an upcoming print edition of the journal.
"We established that less than 1 percent of an egg's tryptophan reserves are used by eggs to communicate with sperm," Zimmer said. "The egg does
|Contact: Stuart Wolpert|
University of California - Los Angeles