See Strange Deep-Sea Creatures, from ‘Sea Pigs’ to ‘Disco Worms’

Meet Some of the Strangest Deep-Sea Creatures, from ‘Sea Pigs’ to ‘Disco Worms’

By Ashley Balzer Vigil edited by Andrea Thompson

An entire world lives deep under the ocean’s surface, far from human notice and as bustling as any city. Animals such as tubeworms and clams live crowded around plumes of methane that bubble up through cracks in the ocean floor. Their residence attracts shrimp, fish and many other creatures. These deep-sea oases are just some of many areas of the ocean floor that scientists are only beginning to explore, discovering new species along the way.

A recent exploratory expedition by the Schmidt Ocean Institute on its research vessel Falkor (too) targeted nearly 20 of these natural underwater gas leaks and five deep-sea canyons off the coast of Chile. Along the way, the research team used its underwater robot to spot a trove of fever-dream characters come to life, including 60 that may be new to science.

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The scientists found methane seeps like this one by combining visual surveys, seafloor mapping and chemical sampling for methane at suspected sites—they even traced telltale bubbles using sonar. Clams huddle around the methane seep so that the chemosynthetic microbes in their gills get a rich supply of food. The microbes convert the methane into organic molecules that the clams absorb as nutrients.

Dense colonies of methane-munching bacteria that build up near seeps are a tasty snack for other organisms, such as these busy little shrimp, seen grazing on a bacterial mat just as cows graze on grass.

Like clams, tubeworms work with microbes to get food from upwelling methane. They also offer anchor points for other creatures, such as the pink basket star, spiky sea urchin and sea star shown here clinging to a brownish, sticklike tubeworm casing near a methane seep.

Creatures such as these sea urchins serve as deep-sea recyclers that break down bits of dead plants and animals that settle on the seafloor and make nutrients available to other organisms. They also attract predators such as sea stars.

This deep-sea anglerfish, which the mission’s researchers are still working to identify, was found in one of five submarine canyons that the scientists explored during the same 55-day expedition. Like underwater Grand Canyons, these formations cut through the ocean floor from near the coast out into the deep sea, carved out by strong currents. Sediment, nutrients and organisms are carried out by the currents like a buffet on a conveyor belt and attract all kinds of hungry sea creatures, such as this fish.

Also found on a submarine canyon floor: a deep-sea worm sometimes called a “disco worm,” but scientifically known as a polychaete (which means “many bristles”), glittering like sparkly steel wool. Its bristles contain tiny protein-based structures that bend and scatter light, which may deter predators.

Scientists also saw this tripod fish, so named because often it stands still on three long, thin fins and lets ocean currents bring it food.

The researchers also spotted this recently identified “mystery mollusk” (Bathydevius caudactylus) swimming far from its known range. The phantomlike creature, a species of nudibranch, had never been seen in the Southern Hemisphere before. It was found more than 7,000 feet beneath the surface, in the ocean’s “midnight zone.”

Some of the researchers’ sightings were more familiar, such as this sea star encountered in another underwater canyon. Its many tiny tube feet help it suction to surfaces such as rocky canyon walls and move along the seafloor.

As scientists sent an underwater robot into the twilight zone, a region of the ocean where sunlight fades to a dim, dusky glow even at high noon, they saw this bioluminescent jellyfish (Colobonema sericeum). It may have been waiting for prey to rise from the ocean’s depths as part of an enormous daily migration.

Here a creature with orange feathery arms called a crinoid perches atop a glass sponge surrounded by clams. Glass sponges create deep-sea habitats for other organisms much like coral reefs do in shallower waters.

The team turned up some of its most bizarre finds in dark ocean expanses between seeps and canyons. This siphonophore—a collection of single cells that teamed up to form a larger creature—was spotted in shallower water near Mocha Island (a small island off the coast of Chile) while scientists were hunting for methane seeps.

Seafloor dwellers must survive the crushing, near-freezing conditions found deep in the ocean. This sea cucumber (nicknamed the “sea pig”) was seen gently drifting more than 9,000 feet underwater. Having that much water pressing down from overhead is like having dozens of elephants stacked on top of your head at sea level. Sea pigs survive the intense pressure partly thanks to their flexible body.

“Through this exploratory expedition, we were able to conduct a raw biodiversity survey and study oases of life on the seafloor, including many places that had never been explored in detail before,” says Jeffrey Marlow, an assistant professor at Boston University and one of the expedition’s chief scientists. “Now we’ll study the samples we collected back in the lab to learn as much as we can about the incredible array of life we saw during the expedition––where these organisms came from, how they’re all connected and what it means for critical functions of this rich ecosystem.”