MBARI Records Rare Magnapinna Squid in the Deep Pacific

In the twilight-like darkness of the deep ocean water column, a whole ecosystem flourishes.

Despite pressure, temperatures and light levels that are profoundly hostile to people, life has evolved a remarkable variety of adaptations.

In new footage, scientists at the Monterey Bay Aquarium Research Institute (MBARI) recorded a rare meeting with one of its most unsettling inhabitants: a Magnapinna squid. Its strange fins and trailing appendages appeared out of the inky darkness of the bathypelagic, or midnight, zone.

This is the first verified observation of the elusive animal in the north-eastern Pacific Ocean.

"At first, I could only see the tips of what looked like fine tentacles, so I thought it was a jelly, but when the 'elbows' showed up on the screen, I knew this was something really special," MBARI deep-sea ecologist Olívia Soares Pereira told ScienceAlert.

"Magnapinna is one of the few, if not the only, deep-sea squid with such fine, long arms and tentacles that can bend like that."

The elusive Magnapinna bigfin squid

Few creatures look quite as uncanny as Magnapinna, commonly called the bigfin squid. It inhabits only the deep ocean, where permanent cold, immense pressure and enduring darkness prevail beyond the reach of sunlight.

The sighting occurred on 7 August under precisely these inhospitable conditions. Using the remotely operated vehicle Doc Ricketts, the research team was surveying the seabed near Davidson Seamount, off Central California's coast.

At a depth of 3,277 metres, the squid floated above the muddy seabed. It softly rippled its pair of huge fins while its eight arms and two tentacles streamed beneath it. From the ROV's laser measurement system, researchers estimated that the animal was about 1.25 metres long from the top of its body to the tips of its arms.

Bigfin squid rank among the least frequently encountered cephalopods. Only roughly 70 specimens have been observed or collected, leaving substantial uncertainty around even the fundamentals of their biology.

"There is actually so little that we know about bigfin squid," Soares Pereira said.

"From submersible sightings, we know they are the deepest-dwelling squids, with one seen an astonishing 6,212 meters – almost four miles – underwater. They are commonly seen hovering over the seafloor with their arms and tentacles extended. We have ideas and hypotheses about why they do that and what the 'elbow' pose is.

"We still have a lot of questions about their basic biology, like what they eat, how they capture prey, how they reproduce, and how rare they truly are."

Bigfin squid anatomy and the distinctive ‘elbow’ pose

Magnapinna is an extraordinary oddity with striking physical proportions. Its mantle is comparatively small and squat, with exceptionally large fins extending from either side. Those fins give Magnapinna its name: big fin. The squid resembles a small torpedo fitted with enormous, flapping wings.

Its appendages are equally remarkable. As with other squid, it has eight arms and two tentacles. In Magnapinna, however, the visual difference between them is far less apparent, since both its arms and tentacles end in exceptionally long, fine filaments. These filaments have been documented at lengths of several metres.

Their unusual nature is not limited to their length. The squid's posture is stranger still. Magnapinna holds its appendages nearly perpendicular to its mantle before sharply folding them at close to right angles, producing the so-called ‘elbow’ pose.

As the squid is so rarely seen, scientists do not know why it adopts this unusual position.

"We still do not know what bigfin squid eat," Soares Pereira explained.

"Based on the behavior of other deep-sea squids, scientists believe they hover over the seafloor to passively capture prey that sticks to their tentacles. The 'elbow' pose could be a part of this feeding behavior, keeping the arms and tentacles extended without getting them tangled up."

Determining just how uncommon these peculiar squid are also remains difficult.

Though encounters are rare, bigfin squid seem to have a broad distribution. Observations have been recorded in the Atlantic, Pacific and Indian oceans, including the Gulf of Mexico, the Mid-Atlantic Ridge, Australia, Hawai'i, the Philippines, Micronesia and the Cook Islands. Consequently, the latest observation does not greatly expand its recognised range.

In fact, a recent worldwide assessment of Magnapinna records indicates that suitable habitat may cover an enormous share of the global ocean: up to 62 percent of its surface area and 70 percent of its volume. Within this vast potential habitat, however, the squid seems to exist at extremely low population densities.

"These scattered sightings make me believe they might be genuinely rare," Soares Pereira said.

"But in a space so big as the global ocean, I think it's hard for us to say for sure if they are genuinely rare or instead rarely encountered, or perhaps even a combination of both. That is why these encounters are always so special!"

Davidson Seamount’s deep-sea life hotspot

This encounter was completely unanticipated, too.

The researchers had not set out to find bigfin squid. Their expedition was examining why Davidson Seamount is such a focal point for deep-sea life, and during this dive they were searching for evidence of an entirely different species.

"Considering that we were specifically investigating furrows on the seafloor that we believe are made by feeding beaked whales, it's exciting to see another animal, and a rare one at that, potentially using the site for feeding too," Soares Pereira said.

Seamounts may serve as oases for marine species. As they rise from the deep seabed, they redirect ocean currents in ways that gather nutrients and food.

Davidson Seamount lies about 130 kilometres south-west of Monterey and is already recognised for its gardens of ancient deep-sea corals, as well as a notable deep-sea octopus nursery.

It now appears that one of the deep sea's most recognisable residents may also benefit from the food it supplies.

"The deep sea never ceases to amaze me. These sightings have given me an even greater appreciation for where I am now and for opportunities that allow me to experience things that once felt so far out of reach," Soares Pereira said.

"These rare encounters are always a reminder of why we do science and how important it is to share my passion and sense of wonder for the deep sea to help inspire the next generation of ocean explorers."

This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. Although we take pride in our process, we are only human. If you notice an error, please let us know.