The Indian spring ant, Harpegnathos saltator, has many talents. This inch-long arthropod, found in floodplains across India, has a vertical leap of four inches and is capable of making prey nearly twice as large. If that wasn’t enough, these amazing ants can also adjust the size of their own brains.
In a study, published Wednesday in the journal Proceedings of the Royal Society B, scientists found that Indian jumping ants can shrink their brains by nearly 20 percent and shrink within weeks. Although it is known that other insects, including honey bees, have the ability to increase their brain size, the Indian spring ant is the first insect known to both increase and decrease brain size. The researchers behind the study say that females of the ant species use this ability to prepare their bodies for reproduction.
Like most ant colonies, those of Indian spring ants consist of a queen, males for reproduction and a female working class. The queen occupies the most popular position in the colony. Queens are not only waited on by workers and ants on hands and feet, but they also live more than five times longer. And in a typical colony, the queen is the only female that may have offspring.
For most ant species, queens are born, not made. However, Indian spring ants are a species with which worker ants can compete for a chance to become royals.
When a Queen Indian spring ant dies, about 70 percent of the females in her colony enter a battle-royal tournament that lasts up to 40 days, where participants beat each other with their antennae until a group of five to ten winners emerge from the battle. tree. These victors spend the rest of their days doing nothing but pumping out babies.
Once the tournament begins, hormones drive the participants to undergo an intense physiological transformation that transforms them into reproductive queen-like ants, called gamergates. Although working ants and gamer holes are the same size, their internal anatomy is completely different.
“If you look inside their bodies, you can see the great transformations they are undergoing,” said Clint Penick, assistant professor of biology at Kennesaw State University in Georgia, and lead author of the new study.
Dr. Penick and his colleagues compared the internal anatomy of workers and gamer holes and found that becoming a gamer hole did not balloon the ovaries of worker ants up to five times their normal size, but that it also increased their brains by about 20 percent. let shrink.
The researchers then used laser-assisted imaging technology to study the brain of gamergate and found that their optical lobes experienced the greatest degree of shrinkage during the transformation. Dr. Penick attributes this to the fact that gamer holes do not require good visibility in their underground nests.
“They live in total darkness, so there is no reason for them to maintain the ability to process visual signals,” said Dr. Penick said.
Workers who turned into gamergate also shrank their central brain significantly. Dr. Penick believes this is because gamergate does not have to perform cognitively difficult tasks, such as finding food and defending the nest against predators.
“Worker ants need a big brain to handle these cognitive tasks, but gamergate doesn’t have to think that much,” he said. “Once they win the tournament, they don’t become much more than egg-laying machines.”
The researchers believe that these ants shrink their brains to conserve energy, a behavior also observed in Etruscan shrews, a small mammal that sheds brain size in winter to keep other body parts warm. It then regrowths its noodle in spring.
“The brain is an expensive organ to function,” said James Traniello, a professor of biology at Boston University who was not involved in the study. “It takes a lot of energy.”
Dr Traniello, who studies the evolution of the brain in other ant species, believes that when female Indian jumping ants turn into gamer holes, most of the energy once spent on the brain is diverted to parts of the body responsible for reproduction.
To see if this reallocation of resources was reversible, dr. Penick and his colleagues collected several newly transformed gamer holes and isolated them from their colonies.
“I thought they would probably just die, but within a few days they completely switched back,” said Dr. Penick said. “It was quite amazing to see that they were able to expand their brains again to exactly the same size as before.”
The researchers suspect that the ability to switch between worker and gamer hole probably evolved to ensure that those who do not succeed in becoming queen can return to their previous role of retaining the colony.
“This species shows an incredible amount of plasticity, both in the larval stage and in the adult stage,” said dr. Penick said. “And so they can be a model to understand things like epigenetics and the control of plasticity in organisms, even to scale people up.”