‘Unusual’ creature found in dark underwater cave turns out to be a new species. See it

Three researchers maneuvered through the darkness of an underwater cave in Japan.

It was the same cave off Okinawa Island where a new species of crab with degenerated eyes and a white body had recently been discovered. So the divers were exploring the cave in hopes of discovering their own rare new creatures, according to a March 5 news release from the University of the Ryukyus.

That’s when — about 100 feet from the entrance of the cave — the team discovered a minuscule creature.

The “unusual” critter was in about 3 feet of water when it was collected, the researchers said in a study published March 5 in the journal Zootaxa.

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After examining the male specimen, the scientists determined the creature was actually a new species of hermit crab: Trichopagurus spinibrachium, or the Dokutsuyawakudaya hermit crab.

The small hermit crab measures less than 1 centimeter, according to the university.

Researchers said the crab has a “polished” and “convex” surface, and its front side has some short bristles. Its beak-like snout, known as its rostrum, is “triangular.”

The new species was distinguished from other species by its physical features, especially by its chelipeds, which are its claw-bearing appendages, scientists said.

Experts described the crab’s chelipeds as “strongly unequal and dissimlar.” The right cheliped is “elongate” and “moderately slender,” while the left cheliped is “slender” and only reaches half of the length of the right cheliped. Both appendages end in “small” claws.

The new species’ name — spinibrachium — comes from a combination of the Latin words meaning “spine” and “arm.” Researchers said they picked the creature’s name because of the “strong spines” on the upper parts of both chelipeds.

The crabs have “moderately slender” walking legs that are a little bit bristly, according to scientists. Their body is mostly white with some pale red blotches, while their chelipeds, legs and other body parts are “orangish brown.”

Although only one specimen was collected from an underwater cave, researchers believe the species could also live in nearby exposed shallow reef walls or other underwater environments.

Okinawa Island is south of mainland Japan in the East China Sea.

Google Translate was used to translate a news release from the University of the Ryukyus.

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