Indian jumping ants shrink their brains to become queen but can grow them back

When it comes to ants, some are very small, like the fire ants that plague the Southern US, and some are quite large. One of the larger varieties of ant is the Indian jumping ant that is about an inch long. As the name suggests, the ants inhabit India's floodplains and can jump about four inches into the air and capture and kill prey about twice its size. The ants also have an incredible ability to adjust the size of their brains.

A recent study focused on the Indian jumping ant and found that they can shrink their brains by nearly 20 percent but grow them back to normal size in a matter of weeks. The ant isn't the only insect species known to have the ability to increase their brain size; for instance, honeybees can increase the size of their brain. However, the ant is the only known insect capable of increasing and decreasing brain size.

Researchers found that Indian jumping ant females can shrink their brains to prepare their bodies for reproduction. The ants are similar to most other ant colonies in that there is a single queen, males for reproduction, and an all-female worker class. Indian jumping ants are one of the only ant species where worker ants can compete for a chance to become the Queen.

When the Queen ant dies, about 70 percent of the females in the colony will begin fighting in a contest lasting up to 40 days where the competitors beat one another until a group of 5 to 10 victors emerges. Those victors will spend the rest of their days producing offspring. As soon as the tournament begins, hormones drive the competitors into a physiological transformation that turns them into reproductive ants called gamergates. They are similar in size to the worker ants, but their anatomy is different.

Researchers say the gamergates have ovaries about five times larger than normal size and roughly 20 percent smaller brains. During the transformation, the team found that the optical lobes experience the greatest degree of shrinkage because the queen ant lives in complete darkness and has no reason to maintain the ability to process visual signals. Workers also need larger brains to deal with cognitively demanding tasks like finding food and defending the nest. The worker ants that don't become queen can grow their brains back to normal size.