Deep-sea octopuses off the California coast are breeding at an unprecedented rate.
Researchers Report February 28 at Virtual 2022 Ocean Science Meeting that the creatures lay their eggs near geothermal springs and that the warmer water accelerates embryonic development.
Because of this reproductive trick, octopus mothers only have to brood for two years instead of the usual 12.
(Photo: Image from NOAA’s Office of Ocean Exploration and Research.)
Thousands of deep-sea octopuses (Muusoctopus robustus) converged on an area of seafloor about 3,200 meters below the surface, according to scientists operating off the coast of California in 2018. The location has been dubbed the Octopus Garden because many creatures the size of a grapefruit were egg-brooding females.
However, with water temperatures around 1.6° Celsius, the development of this garden was to be slow. According to marine scientist Jim Barry of Monterey Bay Aquarium Research Institute in Moss Landing, California, embryonic development slows in octopuses at low temperatures. “When you’re freezing, around freezing, that’s when spawning periods get incredibly long.”
A distinct species of octopus living in warmer waters holds the record for the longest brood length of any animal, just over four years (SN: 7/30/14). According to Barry, Mr. robustus, which thrives in the frigid depths of the Octopus Garden, was a viable candidate for the title. It has a projected spawning period of nearly 12 years at 1.6°C.
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Visit the octopus garden
From 2019 to 2021, Barry and her colleagues used a remote-controlled vehicle to visit the Octopus Garden several times to check out what would be a record-breaking maternity stay. The researchers used cameras to track the growth of octopus eggs, which look like white fingers.
The researchers also gently pushed aside dozens of octopuses and assessed the water temperature in their nests using one of the submersible’s robotic arms. They also found that all the clutches of eggs bathed in moderately warm water (up to 10.5°C). Researchers have found that female octopuses prefer to lay their eggs in streams of geothermally heated water.
This discovery served as a wake-up call that these animals are not the distant mothers people thought they were. “We are almost certain that these creatures are reproducing at a much faster rate than expected.”
Barry and his colleagues concluded that the mothers only brooded for about 600 days, or about a year and a half, based on observations of maturing eggs.
According to Jeffrey Drazen, a deep-sea biologist at the University of Hawaii at Manoa who was not involved in the study, it’s much faster than expected. “They dramatically reduce their period of parental care.”
Shorter incubation times mean fewer eggs are likely to be eaten by predators, which is an evolutionary advantage of seeking warmer water. And these octopuses seem to be aware of it, according to Barry. “We believe they are using this heat energy to help them reproduce more successfully.”
Only a few other sea creatures are known to seek warmer conditions when mating, such as icefish in the Weddell Sea in Antarctica (SN: 01/13/22). But, according to Drazen, other species are likely to do the same. The problem is finding them and their nesting habitats in the vastness of the deep ocean. “I’m sure we’ll continue to uncover incredibly intriguing areas that are crucial to various species as we continue to explore,” he adds.
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