crab
April 13, 2016

VIDEO: Scientists find incredible swarm of red crabs in Pacific Ocean

Marine biologists working in the Pacific Ocean off Panama have observed an incredible collection of red crabs that were "swarming like insects," Live Science reports.

At highest density the crabs numbered 78 in a single square meter - about seven crabs per square foot.

Normally seen in Baja California waters and off the coasts of southern and central California during El Niño events, the crabs had a truly spectacular way of making their presence known this far south for the first time.

'Mini lobsters'

Jesús Pineda, a biologist at Woods Hole Oceanographic Institution (WHOI) and chief scientist among the researchers, said: "To find a species at the extreme of their range, and to be so abundant, is very unusual."

Pineda and his team were in a submersible investigating biodiversity at the Hannibal Bank seamount, an underwater mountain and ecological hotspot, when a disturbance in the water alerted them to something worth looking at. They found the swarm at depths of 1,165 feet to 1,263 feet (355 to 385 meters). As well as being further south than usual, they were at greater depths than usuall. Pineda believes this may be because they were trying to evade predators at oxygen-poor depths.

DNA analysis showed the crustaceans in the swarm to be Pleuroncodes planipes, red crabs that look like mini lobsters. Adults in the species have a hard outer shell measuring up to 1.3 inches (3.3 centimeters) in length.

The find is a reminder that while seamounts are known to have rich biodiversity, there is still much to learn about how the weird and wonderful behavior of the lifeforms they support.

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Image credit: Jesús Pineda et al