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10 April 2014 11:44 am ,
Vol. 344 ,
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
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ScienceShot: Homing in on Sea Urchin Eggs
18 September 2012 10:49 am
For sea urchin sperm, finding an egg to fertilize in a vast ocean might seem like looking for a needle in a haystack. But the prickly creatures have devised a way to shorten their search: The eggs release a chemical homing beacon to help guide the sperm. Now, scientists from the Center of Advanced European Studies and Research in Bonn, Germany, have homed in on just how the sperm use this "chemotaxis" to navigate, the team reports this week in The Journal of Cell Biology. Scientists knew that the eggs of the sea urchin (Arbacia punctulata) release a small molecule called resact, which binds to receptor proteins on a sperm's tail, or flagellum. That allows calcium ions to enter the cell, and the increase in calcium controls how the sperm's flagellum beats, causing sperm to make either sharp turns or slow bends. To better understand the navigation mechanism, the team placed sea urchin sperm in tiny chambers, added a modified version of resact at precise time intervals, and recorded videos of their flagellum movements and of the calcium influx simultaneously. Rather than setting off immediately, the team found, the sperm first test the waters—sampling the resact for 0.2 to 0.6 seconds before determining the right way to go—in the direction of highest concentration. This sperm navigation system might be used by other species, the authors suggest, and their experimental tool provides a template for future studies of chemotaxis in other species, including humans.
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