A team of researchers exploring the remote South Sandwich Islands in the South Atlantic has encountered a remarkable deep-sea creature that appears to be "all legs."
The discovery was made during an expedition by the Schmidt Ocean Institute, which has been using research vessels and remotely operated vehicles to explore the region's unique underwater ecosystems from Feb. 20 to March 28.
According to a March 18 Facebook post from the institute, while operating a deep-sea robot nearly 7,000 feet below the surface, researchers captured footage of an unusual marine arthropod scuttling across the seafloor.
"Huge spider alert! This is a pycnogonid," researchers announced.
Pycnogonids, commonly referred to as sea spiders, are distant relatives of land-dwelling spiders. Unlike their terrestrial counterparts, however, they appear to lack a central body, making them look as though they are nothing but legs.
"Technically, they are not all legs; they do have additional appendages. They also lack lungs and breathe through their exoskeleton," researchers explained. "There are about 1,500 known species in our global ocean, and they range in size from infinitesimally small to large enough to rival a dinner plate or moderately-sized serving platter."
The impressive size of some sea spiders is attributed to a phenomenon known as deep-sea gigantism, particularly common in polar regions, the institute said. "Immense pressure and frigid temperatures, while insurmountable obstacles to land-lovers like humans, allow some animals to have very slow metabolisms and the ability to reach gargantuan proportions," the post stated.
Larger body sizes are also supported by higher concentrations of oxygen in deep-sea environments, reducing growth limitations.
According to the Monterey Bay Aquarium, sea spiders possess eight spindly legs and a long mouthpart called a proboscis. Their organs are housed inside their legs, with intestines extending into pouches at the leg ends. Rather than using lungs, they absorb oxygen through their exoskeleton.
Sea spiders are known to be efficient predators, using their legs to traverse the seafloor in search of food. When they locate soft-bodied prey such as sponges or mollusks, they use their straw-like proboscis to pierce the animal's flesh and "suck out its insides like a smoothie," according to the aquarium.
The South Sandwich Islands, located east of Argentina and north of Antarctica, are among the world's most remote island chains. The region is home to a variety of deep-sea features, including hydrothermal vents, seamounts, and deep-sea trenches, as well as species found nowhere else on Earth. The Schmidt Ocean Institute's ongoing expedition aims to uncover new and rare marine life in this largely unexplored part of the ocean.
