Ravioli Starfish That Scientists Know Virtually Nothing About Spotted During Deep Ocean Dive Off U.S. East Coast

An ocean expedition conducted by the National Oceanic and Atmospheric Administration has come across something unusual in the waters off the southeastern United States.

Researchers aboard NOAA's Okeanos Explorer vessel say they have frequently spotted a type of starfish which resembles a piece of ravioli—the popular Italian dumpling made that's with pasta dough.

The species—Plinthaster dentatus—is known as the "ravioli" or "cookie" star due to its characteristic appearance, according to a blog post on NOAA's Ocean Exploration and Research site.

In contrast to most other starfish, P. dentatus's arms are much less pronounced, merging with the main part of its body. As a result, it has an almost pentagonal shape.

While the species was first discovered in 1884 and has been recorded multiple times in the past, scientists actually know very little about its biology and behavior.

During the latest expedition, researchers were able to observe the animal and record some of its everyday activities. Of particular interest, the scientists managed to capture images and video of numerous feeding events.

On one occasion, the NOAA team witnessed a strange "feeding frenzy" where several large ravioli star individuals and a massive cidaroid sea urchin were all munching on a glass sponge—a deep-sea animal named for its intricate glass-like skeletal structure.

"At least six individuals were involved," Chris Mah, from the National Museum of Natural History, wrote in the blog post. "This prompts many questions! Is it by chance that they are all in the same place? Is this sponge damaged and the sea urchins taking advantage? Is this a common occurrence?"

Starfish are known to feed on glass sponges despite their sturdy, glass-like skeleton and ability to produce various defensive chemicals.

ravioli starfish
Plinthaster dentatus, the "ravioli" starfish. NOAA Office of Ocean Exploration and Research, Windows to the Deep 2019

The Okeanos is the "only federal vessel dedicated to exploring our largely unknown ocean for the purpose of discovery and the advancement of knowledge about the deep ocean," according to the NOAA.

The 224-foot vessel contains a host of advanced technologies which enable to it study ocean phenomena and marine life. These technologies include sonar mapping equipment and a remotely operated vehicle which can dive up to depths of 19,700 feet.

Currently, the Okeanos team is investigating coral and other marine environments in the Atlantic Ocean. Expedition researchers have spotted several other unusual echinoderms—the large group of animals to which starfish and sea urchins belong—in addition to P. dentatus.

These include strange "slime stars" which are capable of producing large quantities of mucus to defend themselves and almost completely transparent sea stars belonging to the genus—or group of species—Hymenaster.

Ravioli Starfish That Scientists Know Virtually Nothing About Spotted During Deep Ocean Dive Off U.S. East Coast | Tech & Science