Octopus Eggs Thrive in Hot Ocean Water of “Octopus Garden”

(p. 14) In 2018, Amanda Kahn, an invertebrate biologist at San Jose State University, joined an ocean expedition to scout the base of Davidson Seamount, an inactive underwater volcano off the coast of central California. She came for the sponges and corals.

But she and her colleagues stumbled across something much more astounding. As their remotely operated vehicle, which was probing the seafloor and streaming video back to their ship, rose from behind a rock, the crew gasped. In shimmering waters, they saw scores of upside-down octopuses nestled in rocky crevices with their arms clutched around their frames. A closer look revealed that they were protecting eggs, similar to the way that birds brood in a nest.

“Sometimes you recognize immediately the magnitude of something special that you’ve found,” Dr. Kahn said. “And I think that was one of those really special moments.”

When James Barry, a marine ecologist at the Monterey Bay Aquarium Research Institute, got a glimpse on a later expedition, he instantly wondered why so many octopuses were here. “And so we set about to figure out,” he said.

. . .

The team’s findings, detailed in a new paper published Wednesday in Science Advances, suggest that this hot spot makes the octopuses’ eggs hatch faster, which improves reproductive success.

. . .

“That’s a big deal for these eggs, because in the deep sea, one of the really big challenges is that it’s cold,” Dr. Barry said. Chilly temperatures slow down the metabolism of coldblooded animals, including rates of embryonic growth. For this species of octopus, it could have taken anywhere from five to 10 years for the eggs to fully develop in ambient waters — but in this nursery, the scientists found that they were hatching in less than two years on average.

The earlier the better, the team reasoned, when it comes to reproductive success. Less time spent as an embryo reduces the risks of being eaten by predators, or suffering infections or injuries that lead to death. Because octopuses don’t eat while brooding — and die after reproducing — they also suspect that quicker egg hatchings might make for a higher chance of survival, since the mother is less likely to lose the energy needed to sustain them.

It’s the mothers’ last hurrah, Dr. Kahn said: “They go all out in protecting those eggs.” She added that brooding near a hot spring helps ensure the mothers’ final acts are a success.

The findings make sense to Michael Vecchione, a deep-sea cephalopod biologist at the National Oceanic and Atmospheric Administration who was not involved in the study. Dr. Vecchione, who had seen the discovery of the garden back in 2018, had also speculated that the octopuses were using the heat to speed up embryo growth. “I’m not surprised that the warm temperature was beneficial to them,” he said. “And apparently, it’s starting to look like it’s a pretty widespread phenomenon, even though nobody had ever seen it until just a few years ago.”

For the full story, see:

Katrina Miller. “Under the Sea, an ‘Octopus Garden’ Thrives in the Shade of a Hot Spring.” The New York Times, First Section (Sunday, Aug. 27, 2023): 14.

(Note: ellipses added.)

(Note: the online version of the story has the date Aug. 23, 2023, and has the title “Atop an Underwater Hot Spring, an ‘Octopus Garden’ Thrives.” The online version says that the print version appears on p. 12. My national edition of the print version had the article on p. 14.)

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