Ants promptly dispose off dead to protect colony

May 6th, 2009 - 4:25 pm ICT by IANS  

Washington, May 6 (IANS) Ants promptly dispose off their dead to protect the colony from infection. But how do they know an ant is dead?
The understanding among entomologists (who study insects) was that dead ants release chemicals created by decomposition (like fatty acids) signalling death to the living ants.

But now University of California Riverside (UCR) entomologists working on Argentine ants provide evidence for a different mechanism for how necrophoresis - the removal of dead nestmates from colonies - works.

Researchers report that both living and dead ants have ‘death chemicals’ continually, but live ants have something more, the ‘life chemicals’. When an ant dies, its life chemicals dissipate or are degraded, and only the death chemicals remain.

“It’s because the dead ant no longer smells like a living ant that it gets carried to the graveyard, not because its body releases new, unique chemicals after death,” said Dong-Hwan Choe, study co-author, working for a doctoral degree with Michael Rust, professor of entomology at UCR.

Choe explained that the research paper’s results resolve a conundrum of long-standing in animal behaviour and correct a misinterpretation of previous results that has become both popular and widespread in literature, said an UCR release.

“There is no mistaking that it is the dissipation of chemical signals associated with life rather than the increase of a decomposition product ‘death cue’ that triggers necrophoric behaviour by Argentine ants,” he said.

These findings were published online in the early edition of the Proceedings of the National Academy of Sciences.

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