28 August 2023
Octopuses are not communal animals. Most live alone their entire lives.
So, scientists were surprised to find thousands of pearl octopuses living together as they protected their developing eggs. The community is on the ocean floor off the California coast.
Now, researchers may have solved the mystery of the strange pearl octopus behavior.
An inactive underwater volcano heats the area where the mother octopuses settle. Their eggs hatch faster as a result.
"There are clear advantages of basically sitting in this natural hot tub," said Janet Voight. Voight is an octopus biologist at the Field Museum of Natural History in Chicago, Illinois. She co-wrote the study published in Science Advances.
The researchers found that the area's warmth greatly reduced the time it took for eggs to hatch. As a result, the eggs had a reduced risk of being eaten by snails, shrimp and other animals.
Researchers discovered the nesting area in 2018, calling it an "octopus garden."
Researchers used a robotic underwater vehicle to film the group of nearly 6,000 octopuses living around 3 kilometers deep.
The octopuses lay their eggs on warm rocks and then remain there, protecting their young with their bodies.
National Oceanic and Atmospheric Administration biologist Andrew DeVogelaere was a study co-writer. He described what researchers saw: "It was completely incredible – we suddenly saw thousands of pearly-colored octopus, all upside down, with their legs up in the air and moving around."
The octopus were pushing away possible predators and turning their eggs for an even flow of water and oxygen, he explained.
But scientists still did not know exactly why the octopuses had gathered there.
Scientists observed the area for three years to understand the hatching process. They recorded both the developmental stage of eggs at 31 nests and the deaths of octopus mothers.
"After the hatchlings come out of the nest and swim off immediately into the dark, the mothers, who never left their nest and never appeared to feed during nesting, soon die," said James Barry. Barry is a biologist at the Monterey Bay Aquarium Research Institute and co-writer of the study.
The researchers found that eggs at this site hatch after about 21 months. The same process takes four years or more for other deep-sea octopuses.
"Usually, colder water slows down metabolism and embryonic development and extends life span in the deep sea. But here in this spot, warmth appears to speed things up," said Adi Khen. Khen is a biologist at the Scripps Institution of Oceanography and was not involved in the study.
Mike Vecchione is a zoologist and octopus expert with the Smithsonian National Museum of Natural History. He praised the researchers for gathering "so much detailed data about such a remote location."
Such octopus gardens "may be widespread and really important in the deep sea," he said. "There's still so much to discover in the deep sea."
I'm John Russell.
Christina Larson reported on this story for the Associated Press. John Russell adapted it for VOA Learning English.
Words in This Story
hatch – v. to be born by coming out of an egg
advantage – n. a good or desirable quality or feature
nest – n. a place where an animal lives and lays eggs
incredible – adj. difficult or impossible to believe
hatchling – n. a very young creature that has just come out from an egg
remote – adj. far away from people, cities, etc.