Ants Stay Clean by Squirting Antimicrobials from Their Butts
Worker leaf-cutting ants emit antimicrobial secretions from a gland in their rear ends.
Credit: Christopher Tranter / ctranter.com

Ants may not seem particularly germaphobic, since they live in bacteria-rich dirt and often eat decaying plants and animals. But some ants have evolved to be quite fastidious sanitizers, regularly bathing themselves in antimicrobial secretions emitted from glands in their rear ends.

Now, research from scientists based at the University of Sussex in the United Kingdom suggests some ants also take it upon themselves to sanitize young, vulnerable members of their colonies by scrubbing their broods and nesting materials with their cleaning fluids.

"We knew that [the secretions] help adults, and we knew that the brood survives and isn't constantly being affected by fungi," study co-author Christopher Tranter told LiveScience. "So we predicted that these secretions would help in keeping the brood healthy as well, and it was nice to find strong evidence showing that." [Mind Control: Images of Zombie Ants]

Tranter and his colleagues studied the cleaning mechanisms in the Brazilian leaf-cutting ant (Acromyrmex subterraneus subterraneus) and the Southeast Asian weaver ant (Polyrhachis dives) by sealing off the antimicrobial-producing glands in a subgroup of their sample using a thin enamel polish. They then placed these adults with broods for about two weeks. They did the same with nonsealed-off ants for comparison. The team also placed sealed-off and nonsealed-off adults among brood-free nesting materials and measured the fungal growth in the materials after about two weeks.

The team found that broods protected by ants with sealed-off glands were less likely to survive than broods protected by antimicrobial-producing ants. In addition, the nesting materials of sealed-off ants contained more fungal growths than nests of nonsealed-off ants did, proving these secretions play an important role in keeping a colony's nursery healthy.  

Not all ant species have evolved to produce these secretions, Tranter said, and some appear to produce them in greater quantities than others. The team next hopes to conduct analyses to gain a better understanding of  why certain species have the cleaning glands and others don't.

The team reported their findings earlier this month in the journal Behavioral Ecology and Sociobiology.

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