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article imageA worm with three sexes found thriving in California's Mono Lake

By Karen Graham     Sep 27, 2019 in Science
The extreme environment of Mono Lake was thought to only house two species of animals -- until now. Scientists have discovered eight new species of microscopic worm thriving in and around the lake, and one of them is a brand new kind of weird.
Researchers at the California Institute of Technology (Caltech) recently discovered the microscopic nematodes and temporarily dubbed them Auanema sp. Further study of the nematodes found that one of the worms had three different sexes, can survive 500 times the lethal human dose of arsenic, and carries its young inside its body like a kangaroo.
The work on the new discovery was done primarily in the laboratory of Paul Sternberg, Bren Professor of Biology. A paper describing the research appears online on September 26 in the journal Current Biology.
Exposed tufa towers in Mono Lake  California.
Exposed tufa towers in Mono Lake, California.
Eeek (CC BY 3.0)
California's "Dead Sea"
Mono Lake, located in the Eastern Sierras of California, is three times as salty as the ocean and has an alkaline pH of 10. Before this study, California's "dead sea" was home to bacteria and algae, as well as a rare species of brine shrimp and diving alkali flies.
Mono lake is also known for its spectacular "tufa towers," calcium-carbonate spires and knobs formed by the interaction of freshwater springs and alkaline lake water. Throughout its long existence, salts and minerals have washed into the lake from Eastern Sierra streams. Freshwater evaporating from the lake each year has left the salts and minerals behind - creating the hyper-saline and very alkaline environment.
Current Biology
As a native Californian, this author can agree that Mono Lake is a strange place. Mark Twain described Mono Lake as a “solemn, silent, sail-less sea,” while Pink Floyd was so inspired by the lake's tufa towers that the band featured them on the sleeve of their “Wish You Were Here” album.
Sternberg laboratory has had a long interest in nematodes. What's so interesting about nematodes is the animal likes to keep things simple. They use only 300 neurons to handle complex behaviors, such as sleeping, learning, smelling, and moving. As for their sexual preferences, the worms like to keep it simple there, too - dividing into hermaphrodites and males.
Eight different species of nematode found in and around Mono Lake  bringing the lake s total animal ...
Eight different species of nematode found in and around Mono Lake, bringing the lake's total animal species (not bacteria or algae) count up to 10.
But Auanema sp. also has worms of the female sex. The worms have other interesting sex characteristics, the study notes, such as "the arrangement of genital papillae in Auanema sp. males is unique in the genus." The researchers note that giving birth to live offspring is a unique approach in the typically egg-laying nematode world.
And nematodes are considered the most abundant type of animal on the planet. For every human on Earth, there are roughly 57 billion nematodes, and in barely no time at all, these creatures can set up shop in some of the most extreme places on Earth, as they have appeared to do in Mono Lake.
This newly discovered species of nematode is considered an extremophile--it thrives under high-salt ...
This newly discovered species of nematode is considered an extremophile--it thrives under high-salt, high-pH, arsenic-rich conditions that are otherwise hostile to life. But it is surprisingly versatile because it can also live in "normal" conditions in the laboratory.
Sternberg lab graduate students Pei-Yin Shih (PhD '19) and James Siho Lee (PhD '19) thought they might find nematodes in the harsh conditions of Mono Lake, and as it turns out, they found a rather diverse group of worms, ranging from benign microbe-grazers to parasites and predators.
Another interesting finding in all the nematodes found is that they were all resistant to the high arsenic levels in the lake, making them truely "extremophiles" - organisms that thrive in conditions unsuitable for most life forms. Another thing the researchers found was that the strange worms could also live and thrive under normal laboratory conditions, suggesting these nematodes have a genetic predisposition for resiliency and flexibility in adapting to harsh and benign environments alike.
More about Mono Lake, nematodes, Arsenic resistance, Auanema genus, otherworldly
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