By TOMOYUKI YAMAMOTO/ Staff Writer
December 12, 2025 at 07:00 JST
Clione Japonica (Provided by Tomoyasu Yamazaki)
A Japanese research team has confirmed a new clione species first found about a decade ago that is believed to have evolved uniquely in the Sea of Japan, according to a newly released research paper.
The species, given the scientific name clione Japonica, is about 4 to 5 millimeters in length. Its body is highly transparent, with orange to reddish internal organs visible through it.
A research team from Toyo Institute of Food Technology based in Hyogo Prefecture, Hokkaido Research Organization and the University of Toyama examined the body, confirmed it as a new species and published the findings in the paper published in November.
“As research progresses, we believe there is a possibility that more clione species will be discovered in the waters off Japan,” said Tomoyasu Yamazaki, a marine ecologist and researcher at Toyo Institute of Food Technology.
Clione species are shell-less gastropods that swim through the ocean by flapping organs called “wing feet.”
To date, four species have been reported, three in the Northern Hemisphere and one in the Southern Hemisphere: clione elegantissima, clione antarctica, clione okhotensis and clione limacina.
Although clione Japonica appears similar to the clione okhotensis, the two species differ genetically and in the shape of the organ on the body surface called lobopods.
The research team believes that the newly discovered species evolved independently in the Sea of Japan from ancestors that evolved in other marine regions.
In 2016, numerous specimens of the clione Japonica were collected in Toyama Bay with a plankton net. In 2018, they were also captured off the Shakotan Peninsula in Hokkaido.
These “mysterious cliones” were suspected to be a new species since the discovery, but its taxonomic classification had remained unclear.
The clione Japonica is thought to travel on ocean currents, and in 2019, specimens were also collected along the coast of Mombetsu in the Sea of Okhotsk and near the Shiretoko Peninsula.
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