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New land snail species discovered in Hawaii offers ‘gem of hope’

The tree-dwelling snails show distinct variation in color and patterning. The holotype, the specimen that officially represents the species, is on the left. Image by Kenneth Hayes and Norine Yeung

  • Scientists recently announced a new species of land snail, Auriculella gagneorum, which was found living in the Waianae Mountains in O‘ahu, Hawaii.
  • There are three known populations of Auriculella perpusilla on O‘ahu, and a small number of snails were selected for a captive-breeding program to help conserve the species.
  • Hawaii once had 752 species of land snails, but more than half of them are believed to have gone extinct due to habitat loss and invasive species.

In the Wai‘anae Mountains, a range on the western side of O‘ahu, Hawaii, a group of scientists were surveying the land for tiny, terrestrial snails when they came across something unexpected.

“There was a tiny snail that we knew its distribution [to be in] the eastern mountains, so having it on the western mountain was like, ‘Okay. Either it’s a new species, or it got transported somehow from its original range,’” Norine Yeung, one of the scientists conducting the surveys and a researcher at the University of Hawaii and the Bishop Museum, told Mongabay.

Auriculella gagneorum. Image by Norine Yeung.

The snail was candy-striped and about half a centimeter (a fifth of an inch) long, and it looked almost identical to another species: Auriculella perpusilla. But when the scientists took the snail back to the lab to conduct a thorough examination of it, they realized it was a different species altogether.

But this wasn’t the first time scientists had stumbled upon this particular snail. When Yeung and her colleagues scoured records in the Bishop Museum, dating back to the 1940s, they found that the snail had already been documented.

“The researchers at Bishop Museum already noted it as a possible new species,” Yeung said. “So they knew about it, but didn’t get a chance to be able to publish it and to report it to the world. It’s been a secret that’s been locked up in the collection.”

Auriculella gagneorum. The light brown snail is a juvenile. Image by Norine Yeung.

In July, Yeung and her colleagues published a paper in ZooKeys about the new species, which they named Auriculella gagneorum after two Hawaiian conservationists, Betsy and Wayne Gagne. While the holotype had a tiger’s eye-like pattern, others are adorned with sable and white stripes.

Hawaii was once teeming with land snails, but habitat loss and the introduction of invasive species, such as predatory snails and rats, has driven more than half of the islands’ 752 land snail species to extinction.

“Rats not only eat the snails directly, but they also tend to eat the plants that were part of the habitat,” John Slapcinsky, co-author of the paper and senior biologist at the Florida Museum of Natural History and the University of Florida, told Mongabay. “There used to be palm forests that are gone because of them.”

“Snails on islands don’t reproduce very fast,” he added. “And so they’re getting eaten faster than they can replace themselves.”

Auriculella gagneorum, bottom row, is a sister species to the high-spired A.tenella, top left. Although it resembles A. perpusilla, top center, and A. perversa, top right, the snails are not close relatives. Image by Kenneth Hayes and Norine Yeung.

Considering Hawaii’s history of extinction, the discovery — or rather, rediscovery — of A. gagneorum has been a beacon of hope.

“For us, it is really exciting because for a long time we’ve been told that pretty much all of the Hawaiian land snails are extinct,” Slapcinsky said. “It really feels good to have something positive.”

“[It] brings that little gem of hope that this isn’t all a depressing story,” Yeung said in a statement.

Three populations of A. gagneorum have been found on Oahu, but it’s hard to get an accurate population count, according to Yeung.

Auriculella gagneorum displayed on a toothpick. Image by Kenneth Hayes and Norine Yeung.

“A lot of assessments are vertebrate-centric, where they can count every single elephant in a population, and they can probably do a pretty good count on the birds in an area, too, because they’re so large or you can hear the songs,” she told Mongabay. “But for the majority of invertebrates, they’re super teeny, teeny, tiny and so to be able to count every single one of them, it’s impossible.”

Yeung, Slapcinsky and colleagues have been conducting surveys of the Hawaiian islands since 2004, prospecting more than a thousand sites. Besides the discovery of A. gagneorum, they also rediscovered several snail species believed to be extinct, including Newcombia canaliculata, Laminella venusta and Auriculella pulchra.

Now that scientists are aware of A. gagneorum, they’re eager to learn more about the species so that appropriate conservation measures can be taken. Like other land snail species, A. gagneorum are susceptible to habitat loss and predation. But there are ways to protect them.

An adult Auriculella gagneorum, left, subadult and juvenile rest on the tip of a toothpick. The snails represent the first new living Hawaiian land snail species described in 60 years. Image by Kenneth Hayes and Norine Yeung.

“There are several exclosures in Hawaii where there are physical barriers (a fence) that is supplemented by salt and chemical barriers and recurved fence lips that keep predatory snails and other predators from scaling the fence,” Slapcinsky said in an email.

Several individuals were also selected for a captive-breeding program, and Yeung says they are “doing well.”

There is hope,” Yeung said. “Even though there’s only three populations … there’s a chance, we can translocate them into a habitat that will sustain this species.”

Citation:

Yeung, N. W., Slapcinsky, J., Strong, E. E., Kim, J. R., & Hayes, K. A. (2020). Overlooked but not forgotten: the first new extant species of Hawaiian land snail described in 60 years, Auriculella gagneorum sp. nov. (Achatinellidae, Auriculellinae). ZooKeys, 950, 1-31. doi:10.3897/zookeys.950.50669