April 20, 2018 - Reviewing underwater footage from the waters off Costa Rica, marine biologists discovered something unusual—hundreds of octopus moms, incubating their eggs. The location, 1.2 miles below the surface, is much deeper than expected to find an octopus nursery. They normally seek out cooler waters to sit with their eggs, but this rocky outcrop is crisscrossed with hot thermal vents. The large gathering is also unusual—these octopuses are normally solitary, and occasionally cannibalistic. None of the eggs were found to be developing, and the octopuses were observed to be under great stress. Scientists think the crevices in the rock offer attractive real estate for the cephalopods.

Nothing about the hundreds of octopus moms on the video feed from the submersible Alvin looked right.

"Those octopus shouldn't be there," Janet Voight, a marine biologist at the Field Museum in Chicago, said when she saw the footage.

The research vessel was exploring a rocky outcrop about 1.2 miles deep and 150 miles off Costa Rica's Pacific coast—far deeper than any other known octopus nursery, and (in theory) too warm.

"It was jaw-dropping," says Anne Hartwell, a research assistant at the University of Akron in Ohio, who led a new study on the 2014 footage of the octomoms guarding their precious eggs. (See our most beautiful octopus pictures.)

With Voight's help, Hartwell identified the plentiful cephalopods as part

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