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These ants can shrink and regrow their brains

Picture of an ant on a green branch
When a colony’s queen dies, Indian jumping ant workers compete in tournaments to decide which individual will become the new head of the colony. The winner undergoes unusual bodily changes, such as a reversible shrinking of the brain.

These ants can shrink and regrow their brains

New research on Indian jumping ants shows they can undergo dramatic reversible changes previously unknown in insects.BYTROY FARAHPUBLISHED APRIL 13, 2021• 6 MIN READ

For most ant colonies, there’s a straightforward hierarchy: a single queen lays all the eggs, while a caste system of workers manages everything else—foraging for food, nursing baby ants, going to war, and so on. Only males and queens can reproduce, and the rest of the ants are sterile. If the queen dies, the colony usually does, too.

Things are different for the Indian jumping ant, a species with forceps-like jaws and large black eyes that inhabits forests along India’s western coast. In these colonies, if the queens die, workers host bizarre competitions in which the winner becomes the monarch—and capable of producing eggs. The triumphant female ant’s ovaries expand and her brain shrinks up to 25 percent.

But new research shows these queens can be taken off their pedestal, reverting back to workers. This causes the ovaries to shrink again, and the brain to regrow, an extraordinary feat not previously known to occur in insects.

“In the animal world, this level of plasticity—and especially reversible plasticity —is pretty unique,” explains Clint Penick, the lead author of the study documenting this discovery, published Wednesday in the Proceedings of the Royal Society B: Biological Sciences.

Game of ants 

Penick, an assistant professor of ecology, evolution, and biology at Kennesaw State University, in Georgia, has spent years studying Indian jumping ants, known as Harpegnathos saltator. When theseworkers shift into queen-like reproductive mode, scientists call them gamergates (not to be confused with the online harassment campaign tied to video games). The term gamergate comes from the Greek for “married worker” and was coined in the 1980s; The “gam” in gamergate rhymes with “ham.”

Every member of H. saltator can reproduce, but this can only occur if an individual wins a drawn-out series of dominance tournaments that take place after a queen dies. Like a tiny jousting championship, the ants take turns rapidly jabbing each other with their antennae.

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