Timing is everything, as lovers know. Susan Brawley, a University of Maine marine biologist, leads a research team which has used that truth, along with the results of biochemical studies with seaweed, to overturn a widely-held principle of reproduction in aquatic organisms.

Their work demonstrates a heretofore unknown biochemical mechanism which makes organisms "exquisitely sensitive" to environmental cues such as water motion and salinity, according to a 1996 paper co-authored by Brawley and her research team.

Brawley gave a presentation today about her team's work at the annual meeting of the American Association for the Advancement of Science in Philadelphia. (For other news about the AAAS meeting, see http://www-leland.stanford.edu/dept/news/release/curindex.html.)

The organisms in question are those which reproduce in the water by external fertilization -- some species of fish, corals, and plants such as seaweeds. The results of previous experiments and modeling studies have concluded that, when it comes to fertilization, these organisms don't have that knack for good timing, i.e., that their rate of fertilization success borders on one percent or less.

These studies have used an underlying assumption that reproductive cells, or gametes, are released when water is turbulent. As a result, gametes would be diluted and dispersed. Few would find their target under such conditions.

In light of the evolutionary success of seaweeds and other organisms which use external fertilization, this line of reasoning struck Brawley as odd. "Selection pressure should act quickly on any characteristic that allows an organism to have fertilization success," she says. The hypothesis of an extremely low success rate doesn't meet this evolutionary test.

Isle of Man

During a 1990 sabbatical on the Isle of Man, Brawley
'"/>

Contact: Nick Houtman
nick.houtman@umaine.edu
207-581-3777
University of Maine
17-Feb-1998