Even among ants, royal status is largely an inherited business. But for Indian jumping ants, a blow to the crown is worth losing a little of your brain – especially since you’ll always be able to develop it later.
Unlike other ant species, jumping Indian ants (Harpegnathos saltator) do not die with their queens. Rather, the selected women participate in monthly boxing matches to decide who becomes the new matriarch. The victorious woman then expands her ovaries and shrinks her brain to three-quarters of its original size.
So far, so bizarre, but scientists have discovered another surreal twist on the historical lives of black-eyed forest animals with jaw-dropping creatures – If a woman is deposed from her royal throne, she will return to his work, shrinking his ovaries, regressing his brain and resuming his previous duties.
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“We found that their brains completely returned to their previous size within a month of returning to a subordinate worker,” the study’s lead author, Clint Penick, an associate professor at Kennesaw State University, told Live Science. “It was quite amazing and this is the first time that reversible changes in brain size at this scale have been reported in an insect.”
As in most other ant species, jumping ant colonies in India are strictly hierarchical. A queen is responsible for laying eggs – the queens of some species, such as the army ant, can produce up to 300,000 eggs a day – and workers protect the colony, raise larvae and hunt food.
Where it differs is what happens once the queen is dead. Most ant colonies shrink slowly after their leader dies, workers die one by one, and royal descendants go on to become queens of their own colonies.
But in an Indian colony of jumping ants, the queen’s death causes more than half of the colony’s females to enter a monthly tour of fierce duels with their antennae. Workers capable of activating their ovaries while delivering and receiving constant antenna feet on the face are then chosen to be the next queens, the researchers said. Once the ritual is over, the new triumphant queens release a pheromone to warn their fellow ants about their royal status.
In a colony of 100 ants, about five to 10 females will become new queens, according to researchers.
Only after gaining the status of queen, these newly created ants underwent some more radical changes. Changes in gene expression and a cascade of hormones, driven by a burst of dopamine, cause the ovaries to balloon five times their original size and the brain to shrink by 25%. The lifespan of these new queens ranges from six months to five years.
“The biggest changes in the brain occur in the optic lobes and the central brain,” Penick said. “The ants that win the tournament become, in essence, laying machines and, in general, they will not leave their nest and will not see the light of day. They also no longer have to hunt, care for larvae or defend their nests. All their needs are taken care of. of, so they do not need the same level of knowledge needed to perform complex tasks. “
To test whether this metamorphosis was reversible, the researchers used a sample of 30 colonies, marking two new queens from each colony. One of the queens in each colony was kept in check and allowed to perform her normal royal duties, while the other randomly chosen were sent into solitary confinement for a month – where they were fed and kept completely isolated from their ants. Soon enough, the new isolated queens stopped laying eggs and returned to behaving like workers.
Upon returning to their colonies, the dismissed workers were captured and detained by their fellows for several hours, probably because of their partially developed ovaries. Once they were released, they returned to their duties as queens. Subsequent dissection, performed six to eight weeks later, showed that the ovaries of the returned ants had shrunk and their brains had returned to full size.
Researchers suspect that this bizarre plasticity may have evolved because the species faces a higher-than-normal rate of queen mortality in their natural nests in the Indian jungle, but they are unsure.
Their study is not the only research that shows that animals transform their brain structure in extreme ways, according to Penick. Singing bird species do the same, regressing the part of the brain involved in learning songs before the breeding season.
“The typical wisdom I’ve heard growing up is that once you lose your brain cells, they never grow back,” he said. “Now that we know this is happening to the jumping Indian ant, it may be common in other species. At the very least, this research shows that even an ant’s brain has the tools to recreate itself and many of its genes, and the regulatory networks involved in it are likely to be similar to other animals, even vertebrates. “
The researchers published their findings on April 14 in the journal Proceedings of the Royal Society B.
Originally published on Live Science