eggs

Abalone plume draws in sperm

U. WASHINGTON (US) — A molecule notorious for making us sleepy at Thanksgiving also makes it easier for red abalone sperm to hit their target.

New research, published in Proceedings of the National Academy of Sciences, could have implications for improving fertilization in mammals, including humans.

Abalone spawn all year long, with females releasing several million eggs and males sending billions of sperm directly into the ocean. To attract sperm, abalone eggs release tryptophan, forming a plume that increases the size of the sperm’s target by as much five times.


Researchers used a lab simulation of an abalone’s natural habitat to determine conditions in which sperm were most likely to encounter eggs and fertilization was most likely to occur. (Credit: Ignacio Vilchuis)

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As abalone sperm float and disperse on natural eddies and currents in the water, the plume “makes it much easier for sperm to locate the egg, and that enhances fertilization,” says Jeffrey Riffell, assistant professor of biology at the University of Washington. “The same kind of fluid motions occur in the mammalian reproductive tract.”

Riffell used a laboratory simulation of an abalone’s natural habitat to determine conditions in which sperm were most likely to encounter eggs and fertilization was most likely to occur.

Trypotophan is an amino acid that plays a key role in organism development and growth. But an egg has to release very little of its reserve to create the plume that attracts sperm.

Abalone don’t seem to suffer the same stuporous effect from tryptophan as humans do, Riffell says.

“In our case, the tryptophan makes us drowsy, but for the sperm cells it actually increases their activity.”

The research is funded by the National Science Foundation, the National Institutes of Health, the National Oceanic and Atmospheric Administration and UCLA’s Council on Research.

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