When eight soldier ants, with bizarre giant heads, were collected in a wild colony of New York, scientists knew that they had found something interesting. The discovery of these giant versions, whose job it is to defend the nest, led researchers to create their own super ants soldiers with the help of hormones, and so understand how the ants, and possibly other social insects, acquire specific forms to work only in the colonies.
What happened is that these ants were abnormal in an ancestral State, one that does not appear to be, apparently, in accidental cases. This phenomenon happens occasionally in some places, as in whales that develop human ancestors or members with tails.
"Already we know for a long time that this type of error occurs," says one of the study's scientists, Abouheif Ehad. "What we are showing for the first time is that there is a potential ancestor, and when provoked by this potential can be released to increase the evolution".
Meet the super soldiers
The species Pheidole morrisi, collected in New York, has normally two types of Ant worker: the smallest, responsible for health care, food, feed and care for eggs and larvae of the Queen; and the soldier, who defend the nest and use their large Mandibles to break seeds brought by the other.
This species does not have super soldiers, but the loggerhead resemble ants that exist in eight species in South America and Northern Mexico. All nine species belong to the genus Pheidole, which houses about 1100 species.
So it makes sense that the "aberrations" reveal something about the origin of the super soldiers among the other eight species.
Fabricating a super soldier
To reveal this mystery, the researchers, led by Rajendhran Rajakumar, observed the development of larvae of super soldiers in two of the eight species which normally produce. (The researchers wanted to study the behavior of p. morrisi collected, but they were killed in the laboratory by other ants).
The role of an Ant in the colony is determined by changes in the environment, during larval development. Adult ants can handle these changes, for example, by applying certain hormones, called pheromones, the larva.
In the first period of development, this change determines whether the egg will turn a Queen or worker, and secondly, determines if it's going to be a soldier or minor worker.
Just before the second change, scientists have applied a chemical that acts as a juvenile hormone in larvae of three species that do not produce super soldiers. This type of hormone is involved in transcription of environment data, such as nutrition, to the identity of the larva. To apply it artificially, researchers crossed the natural barriers and created super soldiers.
But these copies of laboratory were not equal to natural ants. As adults, the super lab soldiers continued with traces of wings, something common that lose when mature. "The potential to be a super soldier is there, but a little raw," says Abouheif.
The researchers also analyzed the expression of a gene involved in the development of the wings, and found similarities between the soldiers induced in the laboratory and the natural. They also found similar changes in two natural species of super soldiers, which indicates that rely on the same development engine.
So, for the super soldiers? They seem to have an obvious function of Defense. During an attack, they use their large heads to block the tunnels of the nest, keeping attackers out. Moreau suggests another reason for stocks of these great soldiers: grind seeds. They manage to grind some larger than the ordinary soldiers.
A genealogical tree of mystery
The research may help solve the mystery of the origin of these super soldiers. A study of Corrie Moreau, revealed that one of the species with super soldiers are near the base of the family tree very near Pheidole, Ant ancestor. The other species with alternative soldiers are scattered by the tree.
According to Moreau, there are two possible explanations for this arrangement: or each developed their own ways to create super soldiers, or the mechanism has evolved from a common ancestor between 35 and 60 million years ago. The work of the team of Abouheif points to the second, that the super soldiers dating from the base of the tree.
The implications go beyond the ants. "The question becomes: ' all insects use a path similar to that of ants with giant head or is this group's special," he says. "This suggests that we should look for paths preserved of evolution, through the tree of life."