Wet weather revives crustaceans prehistoric heritage

2005-06-29T23:00:00Z Wet weather revives crustaceans prehistoric heritageALLISON BATDORFF Gazette Wyoming Bureau The Billings Gazette

CODY - Three-eyed, hairy-legged creatures stir in the mud of Red Lake. They've crawled the Earth for 220 million years. They eat aggressively, fight and cannibalize. They've slept for a decade, and now they're very, very hungry.

Don't run screaming or hide your children. Put the pitchfork down. They are just the inch-long Triops longicaudatus, otherwise known as the tadpole shrimp. The crustaceans returned to Red Lake after the long Wyoming drought, kicking off a life cycle that predates the dinosaurs.

"Every time this happens, I get phone calls. People say 'There are trilobites in Red Lake!' " said Cody High biology teacher Dan White. "But they're not trilobites. They aren't horseshoe crabs either, but they look like them."

"Triops" hail from the supercontinent of Pangea - Earth's singular land mass that started separating 237 million years ago. Because tadpole shrimp are eons older than fish, they can't defend against them. So the tadpole shrimp pop up where fish aren't - in muddy, alkaline pools that dry up completely.

This trick-called "diapause"- let the tiny triops outlive the dinosaurs. With short life cycles of 20 to 90 days and unbreakable egg cysts that can stay dormant for 25 years, the tadpole shrimp stay in suspended animation until the time is right.

"They can literally wait years for a good rain, and then they come out in abundance," White said. "Their life cycle starts, finishes and then they disappear."

Triops - "three eyes" - have two eyes on top of their shell, a third underneath and a forked tail. They start from an egg, moving quickly to the larval stage where they double in size every day. Little, they look like a "pistachio nut," said Cody resident Dewey Vanderhoff.

They begin digging for food as soon as their 11 pairs of legs let them. They eat and breathe with their legs, subsisting on invertebrates, plant matter and each other, if there is no other food around.

Tadpole shrimp also munch Culex mosquito larvae, which make them an ally in the battle against West Nile disease. They are also used as a biological agent in Japan, where they eat weeds in the flooded rice paddies.

Tadpole shrimp are found everywhere on Earth, save Antarctica. In some places they are considered a pest, while in Europe, they are on the threatened species list. Triops are called the three-eyed "Billabong bugs" in Australia after the mud holes that appear in the rainy season. They are so common in America and Australia,that one can mail-order them like sea monkeys - "You too can grow a pet from the era of the dinosaurs" - and raise them at home.

At Red Lakes, an area just south of Cody, their presence is part of a strange ecosystem that only appears during wet weather. Most of the year, Red Lake is a four-wheeling haven for drivers of all-terrain vehicles and heavy-duty trucks. Now, resilient triops and tadpoles thrash in the water-filled wheel tracks. The presence of triops also indicates a good chance of a spadefoot frog hatch, said White.

"You'll want to look for those," White said.

The frogs eat the shrimp, the birds eat the shrimp and frogs, and the Red Lakes wet-season food web continues spinning. And when Red Lakes dries up again, those who've seen the water roil and bubble with activity will know of the prehistoric life that lies beneath the mud, biding its time.

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