Scientists have discovered a cluster of more than 100 octopus mothers and their eggs miles beneath the ocean surface during a deep-sea expedition off the Pacific coast of Costa Rica.

The scientist made the unexpected discovery while they were exploring the Dorado outcrop, a rocky area of the ocean floor formed by an underwater volcano.

Submersible cameras captured hundreds of purple octopuses protecting clusters of eggs attached to the outcrop where warm liquids flow.

A Puzzling Discovery

The discovery baffled researchers. For one, similar octopus species prefer cold waters. The researchers were surprised to see the octopuses huddling in volcano-warmed waters. Octopuses in that group also tend to be loners and do not gather in dense communities.

"When I first saw the photos, I was like 'No, they shouldn't be there! Not that deep and not that many of them," said Janet Voight, from The Field Museum.

Deadly Location For Octopuses And Their Eggs

The researchers said that is highly unlikely that the creatures were there because it was a desirable place for them to lay eggs. The heat also increases the metabolic rate of octopuses causing them to need more oxygen.

The water from the cracks in the outcrop also carries less oxygen than the surrounding areas, which means the conditions in this area could be disastrous and even deadly for the mother octopuses and their eggs.

The eggs were, in fact, dying because of the warm water. The researchers said that they did not observe any sign of embryos moving inside the eggs. They also observed that the cephalopods there showed signs of severe stress.

"None of the 186 eggs closely examined showed embryonic development," Voight and colleagues reported in the journal Deep Sea Research Part I: Oceanographic Research Papers. "The increased temperature and limited oxygen of the discharging fluids may threaten the octopods' survival."

Why The Octopuses Were There

Voight and colleagues think that the creatures were there because the conditions around the rocks were not as dire as when the marine animals attached their eggs. The warm and oxygen-poor liquid may have initially been weaker and may not even be there when the octopuses arrived. The octopuses likely did not want to abandon eggs once these were in place.

There is also the possibility that these octopuses were just forced to relocate into this undesirable area because there was overcrowding in a cooler and more desirable part of the rocky outcrop.

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