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Opihi evolution ensures species' survival in isles

By Gary T. Kubota

LAST UPDATED: 3:34 p.m. HST, Jul 10, 2011

The opihi is one Hawaii marine species that won't die off in the face of assaults from alien species.

A study recently found that the Hawaii shellfish is managing to survive by making physical changes to become new species able to survive in a shifting environment.

University of Hawaii researcher Christopher Bird said the shellfish species that migrated from Ogasawara, Japan, and initially settled in Hawaiian waters 5 million years ago has changed to become three different species — the ‘opihi makai‘auli, ‘opihi ‘alinalina and ‘opihi ko‘ele.

The findings for the federally funded study were published in the journals Molecular Ecology and Integrative & Comparative Biology in May and June, respectively.

Bird, who works at the Hawaii Institute of Marine Biology, said the discovery was made while he was conducting the study at various locations on Hawaii island, Maui and Papahanaumoku­akea Marine National Monument to determine environments where they thrive and required the help of community volunteers as well as the Nature Conservancy and state officials.

Opihi, especially the yellow-foot (‘alinalina), is an island delicacy that sells for $15 to $40 a pound.

Residents are reluctant to provide the location of ‘opihi colonies, and Bird would not disclose the exact location of the research.

The opihi makai‘auli, the one most similar to the Japan shellfish but adapted to a warmer environment, is found at higher shoreline elevations, while the opihi ko‘ele is found up to 10 feet below the surface.

Bird said the opihi ko‘ele developed about 2 million years ago with a thicker, flatter shell to withstand crushing bites from ocean predators, including crabs and eagle rays.

The opihi ‘alinalina, which developed about 4 million years ago, has a long tentacle that allows it to evade predators for short distances, then stick hard to rocks to survive the constant wash of waves without increasing its chances of getting eaten, he said.

Hawaiian marine species, such as the Hawaiian monk seal and the Hawksbill turtle, are facing extinction, and the loss of reef fish in the main Hawaiian islands is threatening the health of some reefs, according to scientists.

But the Hawaiian opihi appears to have found a way to survive.

Bird said he and other researchers are looking at the development of the opihi ko‘ele and the possibility that the ‘opihi is splitting into perhaps a fourth species and moving to deeper habitat.

"It looks like it's diverging," he said.

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