‘Dwarf’-like sea creature with see-through shell found in Japan. It’s a new species

On a sandy coastline of Japan, a small and “bizarre” sea creature went about its day, crawling around beneath the rocks. The “dwarf”-like animal was hard to find, but when scientists tracked it down, it turned out to be a new species.

Hiroshi Fukuda, a researcher and associate professor at Okayama University, first encountered the rare snail when he was a student over 30 years ago, he said in a Dec. 29 news release from the university.

Ever since Fukuda’s initial encounter, the tiny snail had become “widely known” in Japan but had never been formally described — until now, according to a study published Nov. 23 in the journal Molluscan Research.

Fukuda studied dozens of the small snails, the study said, and quickly realized he had discovered a new species: Xenassiminea nana, or the strange dwarf snail.

Strange dwarf snails measure less than a tenth of an inch in length, the study said. Fukuda named the new species after the Latin word for dwarf, “nanus,” because of its size.

Several photos show the strange dwarf snail. It has a “shiny,” see-through spiral shell and a pale white body with black eyes, the study said. Fukuda described the new species as “bizarre.”

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Strange dwarf snails are “very active” and able to crawl “rapidly” with “step-like” movements, Fukuda wrote in the study.

The new species “lives in narrow spaces under rocks or in gravel deeply buried in sandy mud … of large bays or brackish water areas of estuaries,” the study said. The animals were “often found crawling on the mud walls” of earthworm burrows and crab burrows.

So far, the new species has only been found “in temperate mainland Japan,” Fukuda wrote.

Strange dwarf snails were likely overlooked because of their size and “unique habitat,” which makes them “difficult to see,” the study said.

The new species belongs to its own new genus, Xenassiminea, the study said. Fukuda named this genus after the Greek word “xeno,” meaning “strange” or unusual,” and the larger family that it falls within, Assimineidae.

Fukuda said he identified the new species based on its shell, internal anatomy and other subtle external features. A DNA analysis was not provided.

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