Fossil throws up oldest example of insect-parasite cooperation

May 15th, 2009 - 5:09 pm ICT by IANS  

Washington, May 15 (IANS) A termite, entombed for 100 million years in amber, has helped researchers unravel the oldest example of insect-parasite cooperation or ‘mutualism’.
Mutualism is a natural process in which two species help each other. In this case, it has established termites as one of the most successful, even if despised, insect groups in the world.

The findings were made by George Poinar, an Oregon State University (OSU) researcher and international expert on life-forms found in amber.

This particular termite was probably flying around while mating in a wet, humid tropical forest during the Early Cretaceous period - the age of the dinosaurs, in what is now Myanmar.

It may have been attacked by a bird or somehow torn open, and then it dropped into the sticky, oozing tree sap that would later become amber, providing an opportunity for the biology of this ancient insect to be revealed in a way that would otherwise have been impossible.

Out of its wounded abdomen spilled a range of protozoa, which even then were providing a key function for the termite - they helped it to digest wood.

Between animals and microorganisms, this is the earliest example ever discovered of “mutualism,” which is a kind of symbiotic relationship.

“Termites live on cellulose, mostly from the dead wood they chew, but they depend on protozoa in their gut to provide the enzymes that can digest the wood,” Poinar said.

“These protozoa would die outside of the termite, and the termite would starve if it didn’t have the protozoa to aid in digestion. In this case they depend on each other for survival.”

Even more primitive termites may have fed on a range of things they could digest themselves, Poinar said, but eventually they acquired protozoa that dramatically increased their ability to digest cellulose, and through evolutionary processes they came to depend on it.

Today, modern termites are one of the world’s most pervasive and successful insect groups, with about 2,300 known species, mostly in tropical settings, busily at work chewing wood or other plant fiber that protozoa help to digest.

They have important ecological roles, helping to create habitat, build soil fertility, recycle nutrients and serve as food for many predators, said an OSU release.

As a social species similar to ants, some termite colonies can have 20 million individual insects. And they also cause massive amounts of damage every year to wood structures in much of the world.

The findings were just published in Parasites and Vectors.

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