Bizarre Blob-Like Sea Creatures of Unknown Species Pulled From Ocean

Scientists have recovered several bizarre blob-like sea creatures in the Pacific Ocean and released photos of their rare find.

The strange animals were collected in the Galápagos Islands by marine biologists Gail Ashton and Kristen Larson with the Smithsonian Environmental Research Center (SERC) Marine Invasions Research Lab.

The creatures are tunicates—a group of marine invertebrates (animals without a backbone)—that live in saltwater habitats around the world, comprising around 3,000 species.

The majority of tunicates, which are sometimes referred to as "sea squirts," spend most of their lives attached to rocks, docks or the undersides of boats, but some species never attach to objects at all and instead spend their entire lives drifting in the ocean.

Their barrel-shaped bodies feature two openings—known as inhalent and exhalent siphons—at one end, while the posterior end is usually firmly fixed to an object. They live by feeding on plankton.

"I often describe them as a u-tube of gut, with an inhalent siphon on one side, and an exhalent siphon on the other," Ashton told Newsweek.

"Their main modus operandi is to bring water into the body through the inhalent siphon, filter and absorb what they need, then squirt what they don't need out the other end. Holding them can often induce the squirt response, hence the 'sea squirt' name."

While these blob-like creatures may look totally alien to us, they are actually our closest relatives in the invertebrate world.

In their juvenile stage, tunicates take the form of free-swimming larvae that look like tiny tadpoles. These larvae have a notochord—a kind of primitive spinal cord. This is lost when the larvae attach to a substrate and morph into their adult form.

These larvae mature extremely quickly—in just a few hours—with their only goal to find a suitable place to settle down. They do not even have mouths at this stage, given that they have no need to feed.

Ashton and Larson collected the tunicates after leaving out devices known as settlement panels—plastic squares measuring around 5 inches across—that the animals subsequently grew on.

"We use settlement panels as a 'collecting device' to monitor for marine invertebrate presence and abundance," Ashton said. "We leave the panels in the ocean, often hung from floating structures, and animals that normally attach to rocks or other structures will settle and grow on the hard plastic surface just as well."

"This makes it easy to collect and study those animals without disturbing the background environment," she said. "The panels that you see in the image that the tunicates are growing on had been attached to a floating pontoon in the Galápagos for three years, which means that some of the settlers had grown to quite a substantial size. Often, we only leave the panels for three months, and the growth is much smaller."

In fact, Larson described those tunicates as "the biggest I've ever seen" in person, having studied the animals for almost two decades.

"[They're] about the size of an average person's hand in a closed fist," Larson told Newsweek.

The settlers in the images are up to three years old, but their exact age is unclear. The scientists only know when they put the panels out, not exactly when the larvae settled.

"As I mentioned previously, often the animals we study are less than three months old," Ashton said. "But, even in the wild, the animals we're used to seeing don't get this big. That's partly a feature of where we work—most of our work is in North America, where tunicates don't typically grow this big and bulbous."

Nevertheless, it is not uncommon for tunicates in other parts of the world to reach these kinds of sizes, particularly when it comes to deep sea specimens—which the Galápagos individuals were not.

The marine biologists said it wasn't clear what species—or even what genus (group of species)—the tunicates they collected from the Galápagos represented.

"It is very difficult—and sometimes impossible—to identify a tunicate by only a photograph," Larson said. "Identification is made by looking at the internal structures after preservation and dissection."

"It is definitely within the Stolidobranchia family. Several of us on site thought it might be of the genus Halocynthia because we had previously found it at the same site many years ago, and it looked very similar," she said. "Many of the species that we identify are small and reoccurring in the bays and estuaries that we survey. So, it is interesting and unexpected to see something different."

The scientists said they preserved some of the individuals they collected in the Galápagos and plan to bring them back to their home laboratory for further investigation.

"Kristen is a tunicate taxonomist and it's her lucky role to dissect some of these animals to study the internal structures to hopefully be able to identify the species," Ashton said.

"Kristen will look at internal features including the branchial basket—which filters all the good stuff out of the inhaled water—gut, and gonads, and compare them to reference descriptions to work out what species they are."

On the outside, tunicates obviously don't remotely resemble humans. But inside, their digestive system looks surprisingly similar to our own, featuring an esophagus, stomach, intestines and a rectum.

Ashton said deploying settlement panels in marinas and ports is one of the key techniques—as marine biologists interested in marine biodiversity—that the pair use to collect data to inform their studies.

"Over space and time, we build a picture of what's present in these environments, as well as how that's changing," Ashton said. "Tunicates are a key group among settling animals growing in all oceans globally."

"Because of their ability to firmly attach and grow on hard surfaces, they are also common among organisms spread and introduced by ships globally," she said. "For this reason, we and our colleagues are quite familiar with a diverse range of tunicates. Fortunately, their diverse colors, shapes and sizes keep us interested as we learn more about them."