This spectacular swarm of red crabs was discovered in low-oxygen waters just above the seafloor at the Hannibal Bank Seamount off the coast of Panama. From whoi.edu:

Jesús Pineda, a biologist at Woods Hole Oceanographic Institution (WHOI) and chief scientist on the cruise, called the encounter unexpected and mesmerizing…

“When we dove down in the submarine, we noticed the water became murkier as we got closer to the bottom,” said Pineda, lead author of the paper. “There was this turbid layer, and you couldn’t see a thing beyond it. We just saw this cloud but had no idea what was causing it.”

“As we slowly moved down to the bottom of the seafloor, all of the sudden we saw these things,” he continued. “At first, we thought they were biogenic rocks or structures. Once we saw them moving—swarming like insects—we couldn’t believe it.”

red-crab-swarm-panama-woodshole

The crabs were later identified by DNA sequencing as Pleuroncodes planipes, a species abundant in Baja California and found in the waters off the west coast of Baja California, Gulf of California, and the California Current…

“No one had ever found this species that far south,” Pineda said. “To find a species at the extreme of their range and to be so abundant is very unusual.”

Learn more about Hannibal Bank Seamount and the science that was conducted on their trip in this mini documentary by Brett Kuxhausen:

Watch more videos about underwater science research, including Two weeks under the sea at Aquarius Reef Base, Researching the impact of sunken shipping containers, and Searching for Life in Iceland’s Frigid Fissures.

Bonus: More swarm videos and more about biodiversity.

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