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Rare bigfin squid first found in Australian waters

By Donna Lu

Bigfin squids are rarely seen because they live in the deep sea

Osterhage et al. (PLOS ONE, 2020) CC BY

The extremely rare bigfin squid, a deep-sea creature found more than 2 kilometers underwater, was first spotted in Australian waters.

Deborah Osterhage at CSIRO in Hobart, Australia, and her colleagues came across the octopus during underwater investigations in the Great Australian Bight, an open bay off the south coast of Australia.

“I knew exactly what it was when I saw it, probably because I’m a bit of a deep sea freak,” says Osterhage. “They are very rarely seen all over the world.” So far, only three sightings had been recorded in the southern hemisphere.

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Bigfin squids (Magnapinna) have a distinctive appearance: they have large fins that make their main bodies almost as wide as they are long, and they also have extremely long, filament-like tentacles that they can bend into an elbow-like appearance. These tentacle filaments are retractable and have tiny suction cups that can be used for feeding.

The researchers discovered the squid for the first time at a depth of more than 2,100 meters during a survey in which a camera was pulled underwater under a ship.

The squid was sighted several times in subsequent investigations. “We were able to find differences in their proportions and their body length to confirm that they are actually five different people,” says Osterhage.

The researchers measured one of the squids with a pair of lasers and found that it was 1.8 meters long and its tentacles were 1.68 meters that length.

The closest distance between two of the five sightings was 300 meters. It was unusual to find multiple Bigfin squids in close proximity, Osterhage says. “Usually you only get reports from one, maybe two.”

Because so little is known about the octopus, more sightings would shed light on its distribution, says Osterhage.

The researchers noticed that some of the squids were curled up in their tentacle filaments, and also observed the creatures very close to the ocean floor. One was in a horizontal position with its tentacles behind, which has never been seen before.

Journal reference: PLOS, DOI: 10.1371 / journal.pone.0241066

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