Hitchhiking sea creature — that can’t swim — turns out to be a new species in Japan

Scientists hauled in their nets off the coast of Japan. Sifting through their catch, they noticed a small, “translucent” sea creature on the surface of a starfish. The hitchhiker turned out to be a new species.

Researchers trawled the depths near Tohoku on several surveys in April 2022, according to a study published Aug. 31 in the Journal of Crustacean Biology. They hauled in starfish, sea anemone and snails but it was a much smaller animal that caught their attention.

The trawls had captured 18 tiny marine invertebrates, the study said. After taking a closer look, researchers realized they had discovered a new species: Janiralata plana.

Janiralata are a group of marine isopods and invertebrate animals classified as crustaceans, researchers said. Janiralata species are parasitic, but they are thought to be “detritivores,” attaching to a host to eat any collected waste or debris.

Janiralata plana is a small sea animal; its body reaching about 0.25 inches in length, the study said. The isopod has a “translucent pale yellow” body that is “smooth” in texture and “flattened” in shape. Researchers said the species “lacks swimming legs.”

Co-author Mizuki Ohta told McClatchy News that Janiralata plana “does not swim.” Still, the species “had a large distribution range,” a finding that Ohta could not yet explain.

Photos show a Janiralata plana specimen. The crustacean appears almost shrimp-like but has antennae on its head and a shorter, straighter tail. Other photos show several Janiralata plana on a starfish and snail.

Researchers named the new species after the Latin word for “flat” or “plain,” a reference to its distinguishing physical features.

Janiralata plana was identified based on its body shape and smooth texture, the study said, DNA analysis confirmed that all collected isopods belonged to the same species.

The new species was found in the Pacific Ocean between depths of about 1,400 feet to about 5,100 feet near Tohoku, researchers said. Tohoku is on the northwestern coast of Honshu island, Japan’s main island, and about 405 miles northwest of Tokyo.

The research team included Mizuki Ohta, Tsuyoshi Takano, Shigeaki Kojima and Yoji Narimatsu.

UPDATE: The article was updated Sept. 12 with comments from Mizuki Ohta.

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