Image Source: Phys
Laying eggs in the warmer water of geothermal springs strategically speeds up the hatching process. Octopuses living in the deep water off the coast of California are reproducing at a far higher rate than anticipated.
According to their findings, researchers reported on February 28 at the virtual 2022 Ocean Sciences Meeting that the creatures deposit their eggs near geothermal springs, and warmer water speeds up embryonic development. Because of this reproductive sleight of hand, octopus moms only have a brood for less than two years, rather than the estimated twelve years.
The deep-sea octopuses (Muusoctopus robustus) gathered on a patch of seafloor about 3,200 meters below the surface of the water, according to scientists working off the coast of California in 2018. As many as a third of the grapefruit-sized critters were females with clutches of eggs, prompting scientists to christen the location of the Octopus Garden.
Due to the freezing water temperatures, which hovered around 1.6 degrees Celsius, it was projected that development in this garden would be slow. According to marine ecologist, Jim Barry of the Monterey Bay Aquarium Research Institute in Moss Landing, Calif., embryonic development in octopuses is slowed down at low temperatures, particularly in the early stages of development. It’s when the weather becomes exceedingly cold, down to or below zero degrees, that brood periods become highly protracted.
The record for any animal’s most extended brood period is held by a different species of octopus that lives in warmer water (SN: 7/30/14), which has a lifespan of slightly over four years. According to Barry, the fact that M. robustus was thriving in the frigid depths of the Octopus Garden meant that it was a serious contender to snag that honor. According to the anticipated brood time at 1.6° C, it will live for more than twelve years.
From 2019 to 2021, Barry and his colleagues visited the Octopus Garden on several occasions with a remotely operated vehicle to confirm what would be a world-record-setting stint of motherhood. The scientists photographed the octopus eggs, like white fingers, to determine their development pace. One of the submersible’s robotic arms was used to gently nudge dozens of octopuses aside, while another was used to measure the temperature of the water surrounding the octopus nests.
The researchers discovered that all egg clutches were bathed in water up to 10.5 degrees Celsius. The researchers found that female octopuses preferentially lay their eggs in streams of geothermally heated water, which they believe results from the water being heated by the sun. According to Barry, this finding served as a red flag that these animals are not the long-distance mothers that humans had assumed. “We’re almost certain that these animals are reproducing at a rate that is significantly higher than expected.”
In their study, Barry and colleagues concluded that the mothers only brooded for around 600 days, or about a year and a half, based on their observations of the growing eggs. According to Jeffrey Drazen, a deep-sea biologist at the University of Hawaii at Manoa who was not involved in the study, this is far quicker than was projected by the researchers. As a result, they’re shaving off a significant portion of their parental care allowance.
Choosing warmer water also has an evolutionary advantage: shorter brood times mean fewer eggs are likely to be eaten by predators, which benefits the species. And these octopuses seem to be aware of this, according to Barry. Few other marine creatures, such as icefish in Antarctica’s Weddell Sea (SN: 1/13/22), are known to seek warmer circumstances while reproducing. This is one of the most compelling arguments in support of their behavior. Drazen believes that additional animals are likely to behave similarly. Finding them and their nesting habitats in the enormous expanse of the deep ocean is a significant problem. “I anticipate that as we continue our search, we will continue to come across incredibly intriguing areas that are critical to certain species,” he adds.