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Wednesday, October 17, 2018

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Specimens A and C are the previously discovered Cryptomaster leviathan. B and D are the newly described Cryptomaster behemoth. Credit: Marshal Hedin Lab Specimens A and C are the previously discovered Cryptomaster leviathan. B and D are the newly described Cryptomaster behemoth. Credit: Marshal Hedin Lab

Hunting Behemoths

SDSU biologists discovered a new and (relatively) enormous species of arachnid in southwest Oregon.
By Michael Price

“When you find one under a log, you’re sort of in disbelief.”

The Curious Aztec takes you behind the scenes of scientific investigation and discovery taking place at San Diego State University.

Marshal Hedin carefully extracts a behemoth from a glass vial using tweezers and puts it under a microscope. He peers into the eyepiece and fiddles with the focus, uses the tweezers to outspread its eight rust-colored limbs. “Beautiful,” he says.

You might not expect something named “behemoth” to fit under a microscope, but it’s a relative term in the arachnid world. With its legs fully extended, the creature is roughly the size of a dime. Still, Cryptomaster behemoth is among the largest short-legged harvestmen ever found in North America. (Harvestmen, sometimes known as daddy longlegs, are arachnids like spiders, but they have a fused thorax and don’t build webs.) Recent genetic analysis has established it as an entirely new species.

A research team led by Hedin, a biologist and arachnid expert at San Diego State University, discovered this specimen in August 2014. Earlier that year, he had received a grant from the National Science Foundation to train a new generation of arachnid hunters, as well as to investigate new methods for finding elusive harvestmen.

Several weeks into an expedition that found the researchers trawling mountains and forestland between northern California and southern Washington, the team was camped out beside the Mackenzie River some 20 miles east of Eugene, Oregon. They awoke to chattering river otters and the sounds of heavy logging activity nearby. In 1969, another monster of a harvestman, Cryptomaster leviathan, was discovered in Oregon, so Hedin and his team knew that giants crawled these lands.

Land of giants

As the morning sun burned off the late summer fog, the scientists found a strip of old growth forest dominated by lumbering oaks and pine trees. They flipped over a decaying log from a fallen fir and there they were.

“We found two of them sitting side by side,” Hedin said.

The harvestmen were a bit larger than C. leviathan and outside its typical habitat range. The team suspected it could be a new species, but would have to wait to get back to the lab before they could confirm it.

Over the course of the trip, the researchers collected 77 specimens of Cryptomaster. After running a genetic analysis and comparing slight differences in the arachnids’ morphology and habitat, Hedin was confident they had found another species of Cryptomaster besides C. leviathan. Following C. leviathan’s lead, SDSU postdoctoral researcher James Starrett and graduate student Shahan Derkarabetian named the new, larger species C. behemoth. The team published the results in the journal ZooKeys.

“The paradoxical thing is, they’re so big, you’d think they’d be conspicuous and easy to find,” Hedin said, “but that hasn’t been the case. When you find one under a log, you’re sort of in disbelief.”

Future discoveries

Even after discovering C. behemoth, plenty of mysteries about it remain. What does it eat? What eats it? When and how did it diverge from its close evolutionary cousin, C. leviathan?

“We know what they look like and where they live, but that’s about it,” Derkarabetian said.

Starrett, the paper’s corresponding author, noted that given the arachnid’s size, it’s remarkable how elusive the species is. That underscores the importance of developing new skills and methods for discovering new species of harvestmen, Hedin added.

“That is ultimately more significant than discovering just another new species,” he said.

There are doubtless other cryptic species waiting to be uncovered in the Cascade Range’s “poor man’s rainforest,” as Hedin calls it, but he doesn’t expect to find any larger than C. behemoth.

“Behemoth is probably about as large as they can get in this part of the world,” Hedin said. “They’re bigger than they should be.”