Triops

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Triops

Marfa Public Radio

Broadcast on September 30, 2010

Triops

A triops in Big Bend Ranch State Park. (Photo by Cathryn Hoyt)

By Megan Wilde

Around this time of year, summer’s showers and stormy theatrics might have made you forget you’re in the Chihuahuan Desert. But soon our rainy season will wrap up its act, reminding us how fleeting it really is. For a triops, life is as fleeting as our summer rains.

These thumb-sized creatures can be found in ephemeral rain-filled pools in deserts around the world. When their homes dry up, triops die. But during the few months they’re alive, they leave eggs that can ride the wind for hundreds of miles and wait decades to hatch when future rains fall.

Who are these unusual animals? And how do they thrive in such precarious and harsh environments?

With rounded shells and long forked tails, triops look like miniature horseshoe crabs or peculiar tadpoles, which is why they’re also known as tadpole shrimp. But they actually belong to an ancient group of crustaceans called branchiopods, which includes the fairy shrimp sold as sea monkeys.

Their name, triops, means “three-eyed” in Greek. Between two bean-shaped dark eyes on their upper shell is a pale dot. This third eye is like a windowed tunnel through their body, allowing them to sense light from above or below.

Underneath a triops are several dozen pairs of wriggling pink legs. Thanks to these appendages, triops are underwater acrobats and can feast on a buffet of pond detritus. As they swim somersaults and backstroke across puddles, they shovel algae, mosquito larvae, frog eggs, bits of decaying plants, and even other triops into their mouths. Their legs serve yet another essential function: they breathe through them. Hence their group’s name, branchiopod—Greek for “gill footed.”

This body shape has worked very well for triops. They can be found on every continent except Antarctica. And they’ve barely changed in more than 220 million years, surviving the dinosaurs’ disappearance. Because they’re spitting images of their Triassic ancestors, triops are often called living fossils.

The secret to their success is their adaptation to life in ephemeral pools in arid lands. As one of few creatures able to make their living in these environments, they have few competitors and evade many predators. And while their days are numbered—quite literally to about 90—they make the most of every moment.

When rain soaks a dusty spot where triops eggs are waiting, their larvae can appear within 24 hours. In only three weeks, they grow into adults, and the females quickly lay a thousand or so eggs. These tough-shelled eggs—technically called cysts—are actually dormant embryos in a state known as diapause. In diapause, eggs can endure the desert’s extremes – freezing, drought and drying winds, and near-boiling heat. They are patient too, waiting sometimes more than 20 years for just the right conditions to start life.

Not only can triops’ eggs survive such conditions, they exploit them. Desert animals visiting the wet spots where triops eggs are laid can become unwitting taxis. The eggs get caked in mud on these animals’ feet, which carry them to distant locales. Wind is another mode of transport. By hitchhiking on a desert breeze, eggs can travel hundreds of miles. Even passing through a duck’s intestine can be part of an eggs’ journey to a new home.

It’s this robustness that has landed triops in another unusual type of habitat. Like their sea monkey relatives, triops are sold as aquarium pets. So if the summer rains leave before you have a chance to meet a triops outside, you can always get to know one in a plastic tank.

Have a question or comment about this episode? Contact Nature Notes Coordinator Megan Wilde at mwilde@cdri.org, or discuss this episode on Nature Notes’ Facebook page.

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Nature Notes is sponsored by the Meadows Foundation and the Dixon Water Foundation and is produced in cooperation with Marfa Public Radio.