Scientists have captured stunning video of a dinner-plate-size sea spider crawling on the seafloor off the South Sandwich Islands, a chain of volcanic islands near Antarctica in one of the most remote areas of the world.
Sea spiders, also known as pycnogonids, are distant cousins of the creepy-crawly arachnids we see scuttling about on land. These creatures can have leg spans of up to 20 inches (51 centimeters) — nearly double those of the largest land spiders, whose leg spans top out at around 12 inches (30 cm).
According to the Schmidt Ocean Institute, which shared the footage, the spider's massive size is a result of deep-sea gigantism, the tendency for deep-sea creatures to grow significantly larger than their shallow-water relatives. In this case, the pycnogonid was filmed at a depth of 6,903 feet (2,104 meters).
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"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," Schmidt Ocean Institute representatives wrote in a Facebook post.
Larger animals can also move faster and farther to find food or to locate a mate, which is important when both are scarce.
Deep-sea gigantism is particularly prevalent toward the poles, where freezing temperatures facilitate slower metabolisms. Schmidt Ocean Institute representatives described sea spiders as both "abundant" and "abundantly large" in polar regions.
There are roughly 1,500 species of sea spider known to science and likely many more yet to be discovered, according to the post. Sea spiders inhabit oceans around the world and range just a few millimeters to the size of a serving platter. The species of spider in the video from the Schmidt Ocean Institute has not been specified.
The largest members of this group are usually found at depths between 7,200 and 13,100 feet (2,200 to 4,000 m), according to the Monterey Bay Aquarium Research Institute.
Instead of spinning webs or creating burrows as land spiders do, sea spiders use a specialized tube-like mouth structure, called a proboscis, to slurp up prey such as sea anemones, jellies and other invertebrates.
This latest footage was taken by remotely operated vehicle pilots as part of the Schmidt Ocean Institute's South Sandwich Islands expedition, a mission to locate and describe new species in these frigid waters. According to the institute, scientists have discovered only 10% of ocean life.
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