A red crab swarm caught on video on the ocean floor off Panama last year has researchers puzzled because it's the farthest south the species has ever been spotted.
The swarm of red crabs, known as the species Pleuroncodes planipes, was spotted just above the sea floor at the Hannibal Bank Seamount in low-oxygen water at a depth of 1,164 to 1,263 feet, according to a
Woods Hole Oceanographic Institution news release.
"No one had ever found this species that far south," said Jesús Pineda, a biologist at Woods Hole Oceanographic Institution. "To find a species at the extreme of their range and to be so abundant is very unusual."
"These crabs have been detected before in similar low oxygen conditions. It could be that these low oxygen waters provide a refuge for this species from predators," Pineda added.
The researchers recorded the video in April 2015 during a month-long expedition to the area in a manned submersible.
The website
Live Science said red crabs are more commonly found in waters off the coast of Baja California, but have also been found in abundance off southern and central California during El Niño events, when western Pacific waters are warmer than average.
Researchers said that seamounts are considered ecological "hotspots" because they are the home of thriving biodiverse communities.
The expedition to the Hannibal Seamount, which was described in the science publication
PeerJ, was conducted to learn what made the area such a rich ecosystem.
"When we dove down in the submarine, we noticed the water became murkier as we got closer to the bottom," said Pineda, who was the study's lead author. "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 sea floor, all of the sudden we saw these things. At first, we thought they were biogenic rocks or structures. Once we saw them moving – swarming like insects – we couldn't believe it," Pineda added.
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