NASA researchers have uncovered evidence that gravity, or the lack thereof, may play an important role in the development and evolution of life. The study suggests fertilization is gravity-sensitive and works differently in the near-weightless environment of space than it does here on Earth.

Using sperm from tiny sea urchins, the research team conducted both ground- and space-based experiments to examine the impact gravity has on the reproduction process.

According to a paper authored by Dr. Joseph Tash, a NASA researcher and a professor at the University of Kansas Medical Center in Kansas City, scientists found gravitational changes may influence a species' ability to reproduce. His team's findings were published in a recent issue of Biology of Reproduction.

"The research shows that fertilization is altered in a microgravity environment," said Tash. "Such alterations have implications for reproduction of plant and animal food and for long-term space habitation by humans. This research will be essential for prolonged space exploration."

The experiments were conducted under a grant from NASA's Office of Biological and Physical Research in Washington. The research program provides investigators with the opportunity to use microgravity or low-gravity environments to investigate the role this fundamental physical force and other space-flight factors have on biological and ecological systems.

"All life is influenced by the pull of Earth's gravity. NASA scientists are conducting research to explore the role of gravity at all levels of biological processing," said Dr. Kathie Olsen, Acting Associate Administrator for Biological and Physical Research at NASA Headquarters. "Without the presence of Earth's gravity, we are able to pursue answers to questions of how living organisms develop."

The research team used sperm and eggs from the tiny marine creatures to study motility and interaction during periods of increased gravity and near weightlessness.

Studies conducted during space shuttle missions showed changes in cell proteins, which stimulated and increased the activity of the sperm cells. However, by spinning the cells in a slow-speed centrifuge to increase gravity, sperm activity was decreased, suggesting fertilization may be inhibited by exposure to increased levels of gravity.

Other members of the team included Shane Kim and William Kinsey from the University of Kansas Medical Center, and Marianne Schuber and Dieter Seibt from the German Aerospace Center, Koln, Germany.