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Giant larvacean and its “house” in Monterey Bay. (Credit: The Monterey Bay Aquarium Research Institute)

After not being properly identified for more than a century, scientists have finally identified the “giant sea blob” recently found in Monterey Bay.

The translucent, sea-dwelling creature has been identified by scientists at the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, Calif as a Bathochordaeus charon, an invertebrate that belongs to a group of sea creatures known as larvaceans.

Larvaceans are common marine animals that are tadpole-like relatives of “sea squirts,” which are usually less than a centimeter in length. However, some “giant” larvaceans can grow up to 9 cm long in the deep sea.

The giant larvacean was last identified by scientists in 1900 and named Bathochordaeus charon by the scientist who first identified it after the mythical ferryman who transports souls of the dead across the river Styx.

It then took scientists more than 100 years to document the creature when it turned up in a routine sample collection by MBARI personnel.

“What’s amazing is that they were able to collect an animal in the 1890’s using the technology of the time and still able to make a great drawing,” Rob Sherlock, MBARI senior research technician, said in a statement. “In many ways we know a lot more about the moon than we do about life in the ocean.”

The MBARI scientists used the remotely operated vehicle (ROV) Ventana to observe the animal during a routine dive.

According to Sherlock, towards the end of the dive he noticed the particularly large larvacean from the ROV control room.

Sherlock said there was confusion as to what the animal was because at approximately 9 cm long the larvacean was exceptionally large. However, he was overcome with joy when he realized onto what he just stumbled.

“We found B. charon. It exists!” Sherlock said as he ran into MBARI Senior Scientist Bruce Robison’s office.

The discovery of the larvacean is important because Sherlock and other scientists want to study the role these marine animals play in transporting food into the deep sea. During their ongoing Midwater Time Series—which provides specific data to investigate the natural variability of oceanic communities at depths below the mixed layer—they have observed several other larvaceans.

According to an article in Live Science, larvaceans eat by filtering food through their shimmering, parachute-like mucus “house” almost a meter in length. They wave their tail to stir the water and pull particles directly into its house. By doing this, large particles get trapped and form a fine dusting of marine “snow” on the house, while the smaller particles pass through, concentrating and then funneling into a feeding tube that goes into the mouth.  

One of the main reasons why there is a dearth of information about larvaceans is because they are not easily collected in nets.

“At MBARI we are fortunate to be able to have very skilled pilots using modern ROVs and advanced sampling equipment,” Sherlock added.

Kristine Walz, a MBARI researcher, also found 12 more larvaceans after reviewing 25 years of archived ROV video.

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