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New species of minute moss beetle discovered in Japan's Ogasawara Islands

A newly confirmed species of minute moss beetle, "Ochthebius sasakii," which inhabits the Ogasawara Islands, is seen. (Photo courtesy of Tetsuro Sasaki, Institute of Boninology)

TOKYO -- A new species of tiny moss beetle has been confirmed in Japan's Ogasawara Islands, a UNESCO World Natural Heritage site in the Pacific Ocean, a team of Japanese researchers announced.


The aquatic insect belongs to the genus Ochthebius. This is the first discovery of a new species in the family Hydraenidae in the islands, according to the team.

The bug's habitat is believed to have been deteriorating recently due to a serious water shortage in the Ogasawaras, home to a great number of endemic species and sometimes known as the "Galapagos of the East."

"We hope it will be a good chance to think about the environment," a team member commented of the beetle's discovery.

The team, including the "Institute of Boninology" Bonin Island research group, confirmed the new species during field surveys commissioned by the Tokyo Metropolitan Government, and published the findings in the Bulgarian international zoological magazine "ZooKeys." Ochthebius is a type of aquatic beetle several millimeters long, which inhabits wetlands, mountain streams, coastal reefs and other such environments. A total of 14 species of the genus Ochthebius have been listed in Japan.

According to the team, the newly confirmed species, scientifically named "Ochthebius sasakii" and called "Ogasawara Sesuji Darumagamushi" in Japanese, is about 2 millimeters long. The team first discovered the bug in 2017 in water dripping from crevices during surveys on Chichijima, Anijima and Ototojima islands. Ochthebius sasakii is smaller than closely related species on the Honshu mainland of Japan or Yakushima Island off the southern coast of Kyushu. It has a shallow concave on its labrum -- a part of the head -- that distinguishes from other species.

The researchers found dozens of the new beetles through continuous observation of their habitat during winter, but the number dropped sharply in the dry summer. The Ogasawara Islands have recently been hit with a serious lack of rain. In 2018 on Anijima Island, the team couldn't find any examples of the beetle as spring water dried up.

Team member Haruki Karube, curator of the Kanagawa Prefectural Museum of Natural History, said, "The discovery of the new species is good news at a time when many insects (on Ogasawara Islands) are being threatened by invasive species and other dangers. However, I hope the finding will be a chance for people to think about the apparent cause of the water shortage, such as climate change."

(Japanese original by Suzuko Araki, Science & Environment News Department)

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