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These Ants Use Mercenaries to Fight for Them

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In the jungles of Panama, a group of farmers ekes out a living by raising fungi for food. They’re peaceful, and when more aggressive neighbors come into their territory, looking for a cut of the crop, they oblige the guests and don’t fight them. While inconvenient, the arrangement pays off sometimes. When even more aggressive outsiders try to take over the farms, the first group of intruders earns their keep by repelling them and protecting their hosts. The not-exactly-welcome guests have their uses, and for the farmers, sharing a little fungus is a small price to pay for protection.

Humans have been using hired brutes to do their fighting for them for ages. Think of Blackwater Security, or Murder Inc., or Westeros’ most charming sellsword. But while the drama playing out in Central America echoes elements of Medieval history and The Magnificent Seven, none of the farmers, heroes, or villains here are people.

They’re ants.

The ants of the genus Sericomyrmex are peaceful farmers. They forage bits of vegetation, bring them back to their nests and grow fungus on them for food. Their lives aren’t all bucolic farmyard scenes in miniature, though. While many ants protect their colonies with specialized soldiers who can deliver powerful stings and bites, these six-legged agriculturalists are poorly armed, and can fight back only with their jaws. Unable to mount much of a defense against stinging foes, they’re regularly besieged by another ant species, Megalomyrmex symmetochus. Queens from this parasite species sneak into Sericomyrmex nests and form their own colonies within them, feeding on their hosts’ fungal crops, and sometimes their larva. They’ll also clip the wings of the virgin farmer queens, preventing them from forming new colonies and turning them into laborers. Instead of trying to fight the parasites and risk death, the farmers put up with them and supply them with room and board.

Biologists have found that the two groups are incredibly common with one another, and in some surveys, almost three quarters of Sericomyrmex nests are infested with Megalomyrmex. Even if they can’t fight back, why haven’t these farmers found some other way to rid themselves of their parasites?

One reason seems to be that the parasite is the lesser of two evils, and a good defense against an even bigger threat.

A third ant, Gnamptogenys hartmani, also raids the farmers’ colonies, taking over their gardens and nests and wiping out the inhabitants. The farmers are as defenseless against these pirates as they are against M. Symmetochus. G. hartmani has mastered a colony-conquering “agro-predator” lifestyle. Just two raiders can obliterate 70 percent of a Sericomyrmex colony, and the farmers that don’t perish usually flee and cede their home to the intruders.

When Gnamptogenys shows up at a Megalomyrmex-infested nest, though, the once unwelcome guest proves to be more of a help than a hindrance. The farmers will hide, while the more aggressive parasite soldiers confront and kill the invaders with their strong jaws and a little bit of chemical warfare. The Megalomyrmex ants possess a potent venom that they dole out through stings and by spraying into the air. It kills some of the raiders, and confuses others. The venom’s toxins appear to disrupt Gnamptogenys soldiers’ ability to recognize their nestmates, causing them to turn on each other and kill their own kind.

The arrangement hinges on a quirk of Megalomyrmex’s lifestyle. They don’t infest, eat, and move on like other parasites, but commit to a single host colony for life. Their success and survival depends on the farmers’ well-being.

To Rachelle Adams, an entomologist at the Smithsonian Institution whose research describes Megalomyrmex’s protective functions, the ants are more like mercenaries than pure parasites. They exploit their hosts, but that cost is compensated for by the defense they provide, and acting as soldiers for the farmers also protects their own interests. When trouble comes knocking, a parasitic win-lose relationship becomes a win-win.

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Animals
Where Do Birds Get Their Songs?
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iStock

Birds display some of the most impressive vocal abilities in the animal kingdom. They can be heard across great distances, mimic human speech, and even sing using distinct dialects and syntax. The most complex songs take some practice to learn, but as TED-Ed explains, the urge to sing is woven into songbirds' DNA.

Like humans, baby birds learn to communicate from their parents. Adult zebra finches will even speak in the equivalent of "baby talk" when teaching chicks their songs. After hearing the same expressions repeated so many times and trying them out firsthand, the offspring are able to use the same songs as adults.

But nurture isn't the only factor driving this behavior. Even when they grow up without any parents teaching them how to vocalize, birds will start singing on their own. These innate songs are less refined than the ones that are taught, but when they're passed down through multiple generations and shaped over time, they start to sound similar to the learned songs sung by other members of their species.

This suggests that the drive to sing as well as the specific structures of the songs themselves have been ingrained in the animals' genetic code by evolution. You can watch the full story from TED-Ed below, then head over here for a sample of the diverse songs produced by birds.

[h/t TED-Ed]

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Animals
Watch the First-Ever Footage of a Baby Dumbo Octopus
NOAA, Wikimedia Commons // Public Domain
NOAA, Wikimedia Commons // Public Domain

Dumbo octopuses are named for the elephant-ear-like fins they use to navigate the deep sea, but until recently, when and how they developed those floppy appendages were a mystery. Now, for the first time, researchers have caught a newborn Dumbo octopus on tape. As reported in the journal Current Biology, they discovered that the creatures are equipped with the fins from the moment they hatch.

Study co-author Tim Shank, a researcher at the Woods Hole Oceanographic Institution in Massachusetts, spotted the octopus in 2005. During a research expedition in the North Atlantic, one of the remotely operated vehicles he was working with collected several coral branches with something strange attached to them. It looked like a bunch of sandy-colored golf balls at first, but then he realized it was an egg sac.

He and his fellow researchers eventually classified the hatchling that emerged as a member of the genus Grimpoteuthis. In other words, it was a Dumbo octopus, though they couldn't determine the exact species. But you wouldn't need a biology degree to spot its resemblance to Disney's famous elephant, as you can see in the video below.

The octopus hatched with a set of functional fins that allowed it to swim around and hunt right away, and an MRI scan revealed fully-developed internal organs and a complex nervous system. As the researchers wrote in their study, Dumbo octopuses enter the world as "competent juveniles" ready to jump straight into adult life.

Grimpoteuthis spends its life in the deep ocean, which makes it difficult to study. Scientists hope the newly-reported findings will make it easier to identify Grimpoteuthis eggs and hatchlings for future research.

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