An ant so unlike all other living ants that it was given an extraterrestrial name has been discovered in the Amazon rain forest, biologists announced today.
The tiny new species is the only known surviving member of an ant lineage that separated from the main family more than a hundred million years ago, DNA analysis revealed.
The pale, eyeless ant appears to be adapted to living underground, possibly surfacing at night to forage.
Its long mandibles suggest that the 0.08-inch-long (2-millimeter-long) animal is a predator, most likely of soft-bodied creatures such as termite larvae.
Christian Rabeling, a graduate student at the University of Texas in Austin, found a single specimen of the new species, thought to be a worker ant, in tropical soils near Manaus, Brazil.
Rabeling's team named the new creature Martialis heureka—"Martialis" means "of Mars"—after Harvard biologist and ant expert Edward O. Wilson, who was not part of the study team, commented on its unearthly appearance.
(Read a 2006 profile of Edward O. Wilson, who has been dubbed "Darwin's natural heir.")
"This beast is totally new to science," Rabeling said.
He and colleagues describe the new ant in a paper published online this week in the journal Proceedings of the National Academy of Sciences.
A Branch All Its Own
While superficially similar to other ants, Martialis differs in many anatomical details, experts say.
"The body characters and structures of this new species are not only unique, but almost bizarre," said Corrie Moreau of the Field Museum in Chicago, who was not part of the new study.
For example, Martialis has long and unusually segmented front legs, along with extended forceps-like mandibles that may be used to drag its prey from soil cavities.
But the creature's genes were even more revealing. A DNA analysis by Rabeling's team showed that Martialis is a relic from an ancient branch on the ant evolutionary tree.
The new species' genes suggest that it broke away from the main ant family before the origin of all other living ant groups, which include 20 subfamilies that together contain more than 12,000 species.
Some of these previously known ant groups do include blind, subterranean species, and recent molecular studies have suggested that these lineages appeared very early in ant evolution.
This has come as a surprise to many experts, since ants as a whole are thought to have evolved from wasplike ancestors with no adaptations to life underground.
But the genetic history of the new species strongly supports the idea that some early ant groups acquired subterranean lifestyles.
"The fact that a single ant … can tell us so much about the evolution of ants highlights how little we know about the diversity of life on the planet," Moreau said.
It remains unlikely, however, that the ancestor of all ants was a blind, subterranean creature, said Philip Ward, an ant expert at the University of California, Davis, who was not involved in the new paper.
"These early lineages [may have] survived competition with later-originating and more aggressive ants by retreating to the underground world," Ward said.
Finding other survivors of ancient lineages could help answer questions about ant origins, and study co-author Rabeling thinks such living relics may be found.
"I believe that many, many undiscovered species are still hidden in the soils of tropical habitats," he said.
"We should act quickly to discover them, before the habitats are destroyed."
for National Geographic News
September 16, 2008
source: National Geographic News