Human sperm cells follow chemical attractants in a beeline path to the female egg, researchers have found. They say identifying the process could lead to advances in contraception and fertility treatments.

In laboratory tests, researchers found human sperm have a receptor, or chemical sensor, that causes the cells to swim vigorously towards a natural attractant.

The study is the first to show sperm respond to a chemical signal by swimming toward the source in a predictable and controllable way, the researchers said.

The sperm-attracting substance called bourgeonal worked in the lab, but scientists don't yet know if the egg produces bourgeonal or some other attractant. Biology Prof. Richard Zimmer of the University of California-Los Angeles said that is the next step, but much more research is needed.

The team also identified another compound, called undecanal, that appears to prevent sperm from responding to bourgeonal.

If natural equivalents are found, researchers may be able to develop techniques to prevent conception without the use of hormones, Zimmer said. For example, the compound could confuse the directional signals sperm follow to the egg.

Co-author Marc Spehr of Ruhr-Universität Bochum in Bochum, Germany, said finding a natural equivalent of bourgeonal could also help screen for the best quality sperm in in-vitro fertilization treatments.

The study appears in Friday's issue of the journal Science.