The tiny black dots on the soggy leaf that Emily King plucked out of Mount Diablo Creek the other day did not look very threatening, but the UC Berkeley biologist knows well how looks can be deceiving.

King, 25, has spent the past year and a half studying the smaller-than-tick-size specks, a dreaded sight for researchers familiar with what an infestation of New Zealand mud snails looks like.

The otherworldly mollusks are among the most invasive alien species in the western United States and have recently spread into waterways in the Sierra and eight of the Bay Area’s nine counties. It is an invasion, no less, of voracious armored critters, and nobody can figure out how to stop them.

The snail’s digestive shield is not good for North American fish, some of which have been found with bellies full of the balled-up snails. The fish get no nutrients from the snails, become weak and are in danger of starving if they swallow too many.

Biologists have reported 50 to 90 percent declines in native invertebrates and fish in waterways where the snails are abundant.

Although there are 13 species of mud snails in New Zealand, only one strain made it to California, all of them genetically identical females, King said. One other strain, apparently transported in ship ballast water from Europe, was found in the Great Lakes, and a third one was found in Idaho, she said, but the vast majority are clones from the same genetic strain that spread into the Golden State.

In their native New Zealand, the snails are kept in check by specialized parasites and three species of fish that can crush the shells.

King intends over the next four years of her dissertation research to unlock the secrets of female asexuality, which might also answer why the males, which cannot reproduce without a mate, even exist. She also hopes to figure out how the snails suspend their metabolism and survive in the stomachs of other animals.

She said her research will focus in on the creatures’ behavior around predators and adaptations to different water conditions and food in Mount Diablo Creek.

“All of those factors will be impacted by a changing climate, likely favoring the snails,” she said. That’s why “we need to find out what are the boundaries and what we can do.”

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