New starfish species discovered in Japan

Starfish are often admired for their beauty and simplicity, but beneath the surface, they hold countless mysteries.

One of these mysteries was recently unveiled with the identification of a new starfish species in Japan, drawing attention to the captivating and largely unexplored underwater world.

The discovery of the new starfish was largely thanks to the efforts of various organizations working in tandem. One institution that played a key role in this discovery was the University of Tokyo.

Starfish: More than just a name

Before we get into the details of how this striking creature was found, let’s debunk a commonly held belief.

Despite their name, starfish are not truly fish. They are more akin to the prickly sea urchins and squishy sea cucumbers.

Seemingly gentle and inactive when found stranded on a sandy beach, starfish are in fact significant predators, boasting up to 50 arms, capable of spanning a meter, and living for decades.

Interesting facts about starfish

Starfish, also known as sea stars, are fascinating animals with extremely unique characteristics. 

Regeneration

Starfish can regenerate lost arms. In some species, an entire new starfish can grow from just one severed arm, as long as part of the central disc is attached.

No brain or blood

Despite their complex behavior, starfish do not have a brain or blood. Instead, they use a water vascular system to circulate nutrients and oxygen throughout their body.

Tube feet

Starfish move using hundreds of tiny tube feet located on the underside of their arms. These feet not only help them move but also allow them to grip surfaces and capture prey.

Predatory behavior 

Many starfish species are voracious predators, particularly of bivalve mollusks like clams and oysters. They can pry open the shells with their strong arms and then evert their stomachs to digest the soft tissues inside.

Starfish species

There are over 2,000 species of starfish found in all the world’s oceans, from tropical coral reefs to the deep sea.

Introducing Paragonaster hoeimaruae

Meet Paragonaster hoeimaruae, the newly discovered species of starfish. This distinctive creature belongs to the family Pseudarchasteridae and boasts a vibrant red and beige color, with five arms, spanning just over 10 centimeters.

The team gathered a variety of species from around Japan between 2021 and 2023. They were collected from shrimp and crab cages used by fishers in Hokkaido and Shizuoka prefectures, in northern and central Japan, respectively, and beam trawl surveys conducted by a Yamaguchi prefectural fisheries research ship.

“We discovered the starfish – newly named Paragonaster hoeimaruae – off the coast of the Izu Peninsula in the Sagami Bay, south of Tokyo. We also found another in the Sea of Japan, northwest of Yamaguchi Prefecture in southwestern Japan,” noted lead researcher Itaru Kobayashi from the Misaki Marine Biological Station of the University of Tokyo.

“They were caught between 150 meters and 350 meters deep, have a well-proportioned body with five arms, and are a beautiful red on the surface and beige underneath.”

The starfish’s name, hoei, was taken from the fishing vessel Hoei-maru, which first collected the specimen.

Despite Japan being home to approximately 250 species of starfish, only four species of Pseudarchasteridae had been observed in Japanese waters until now. The astounding discovery of this new species highlights the rich diversity of marine life in Japan.

Species diversity in Japanese waters

Interestingly, the researchers also recorded other starfish species in locations different from where they had previously been found. One such starfish was Gephyreaster swifti, an impressively large starfish roughly 30 centimeters in diameter, found off the north coast of Hokkaido.

Until this moment, it had only been recorded across the Pacific west coast of the United States and Canada, all the way to islands in the Bering Sea to the north.

“About 250 species of starfish live around Japan, and we were surprised that one so large as this had been overlooked. Our research highlights how the diversity of species in Japanese waters is still underestimated,” said Kobayashi.

The exciting research further highlights the value of community-driven scientific endeavors.

“These exciting discoveries show how important it is for fishers, aquariums, universities, and other research institutions to work together to better understand our oceans and marine biodiversity,” said Kobayashi.

Paragonaster hoeimaruae is a testament to the beauty, mystery, and vastness of our oceans. It’s a call to all of us to invest more effort into exploring our marine environment, ensuring its preservation for future generations.

The study is published in the Journal of Natural History.

Image Credit: I. Kobayashi

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