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12 December 2013 1:00 pm ,
Vol. 342 ,
The iconic 125-year-old Lick Observatory on Mount Hamilton near San Jose, California, is facing the threat of closure...
Recent results from the Curiosity Mars rover have helped scientists formulate a plan for the next phase of its mission...
A new, remarkably powerful drug that cripples the hepatitis C virus (HCV) came to market last week, but it sells for $...
In pretoothbrush populations, gumlines would often be marred by a thick, visible crust of calcium phosphate, food...
Evolutionary biologists have long studied how the Mexican tetra, a drab fish that lives in rivers and creeks but has...
Victorian astronomers spent countless hours laboriously charting the positions of stars in the sky. Such sky mapping,...
In an ambitious project to study 1000 years of sickness and health, researchers are excavating the graveyard of the now...
Stefan Behnisch has won awards for designing science labs and other buildings that are smart, sustainable, and...
- 12 December 2013 1:00 pm , Vol. 342 , #6164
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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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