Washington, Apr 22 (ANI): In mouse, sperm tend to gang up with their closest kin to get an edge in the race for the egg, according to a new study.
Once inside a female, sperm cells can discern and-via structures on their heads-literally hook up with their brethren amid the crush of sperm from other males.
Then, the cells can draft, Lance Armstrong-style, moving faster than they could alone thanks to more "engine" power from the cluster, said study co-author Heidi Fisher, an evolutionary geneticist at Harvard University's Hoekstra Laboratory.
"It's really amazing that this single cell can do this. We used to think of sperm as packs of DNA with really fast tails. But [now we know] they're able to make these complex organizations," National Geographic News quoted Fisher as saying.
Surprisingly, the sperm cells' recognition skills are "incredibly refined," added Fisher.
In the experiments, sperm could pick out other sperm from the same male, even when the other sperm were from closely related mice.
The researchers studied the oldfield mouse, which mates for life, and a related species, the highly promiscuous white-footed mouse.
Female white-footed mice will mate with multiple males several times within a minute.
The team extracted sperm from several individuals of each species and mixed two samples in four different combinations.
In each case, sperm from one male was dyed to glow green under UV light, while the other's sperm glowed red.
In both species, sperm formed groups, which swim significantly faster than single cells.
But in every experiment involving white-footed mice, the sperm clustered specifically with their brothers.
However, how the cells recognized each other is still unknown.
One theory is that related sperm express a certain protein on their heads that acts as an identifier, according to the authors.
The researchers also noted that the teamwork lasted just two hours or less, until the sperm reached the egg-the brotherly love ended when individuals became rivals for breaching the egg.
On the other hand, the oldfield mouse sperm formed random groups without family ties, according to the study.
The results support the long-held view that competition drives the evolution of sperm behaviour, said Fisher.
The study has been published in the journal Nature. (ANI)