This elusive deep-sea squid remains shrouded in mystery.

In four decades of deep-sea exploration, MBARI researchers have logged just two encounters with the bigfin squid (Magnapinna spp.). The first was observed by MBARI geologists while studying the volcanic geology offshore of O‘ahu, Hawaiʻi, in 2001. We did not see another Magnapinna for 25 years, when MBARI scientists and NOAA collaborators caught a glimpse of one hovering just above the abyssal seafloor near Davidson Seamount, offshore of Central California, in 2026.

Only about 70 Magnapinna have ever been seen with submersibles or collected from scientific trawls. First collected in 1883, this unique squid was not described by scientists until 1998. Scientists have still never collected an adult Magnapinna specimen, only damaged juveniles, making video footage even more valuable for understanding the natural history of this remarkable animal. While bigfin squid paralarvae live near the surface, Magnapinna holds the record for the deepest-dwelling squid, with one seen at a depth of 6,212 meters (20,380 feet, or almost four miles) in the Philippine Trench in the Western Pacific. 

Magnapinna move with undulations of two large fins. Their elongated teardrop body trails eight arms and two tentacles, each bearing a long, adhesive white filament covered in tiny suckers. These spaghetti-like appendages earn them the nickname “long-armed squid.” The filaments extend from a 90-degree, elbow-like joint, and may be up to 20 times the length of the squid’s body.

Bigfin squid are often observed near the seafloor. They spread their arms and tentacles wide open, dangling their thread-like filaments far beyond their body, sometimes appearing to “walk” with them across the bottom. When disturbed, those fine filaments recoil quickly. Many deep-sea squids use their long tentacles to fish for a meal, so scientists suspect these filaments may serve the same purpose—though we still do not know what is on the menu for Magnapinna.

We still have many unanswered questions about the bigfin squid. Continued advancements in ocean exploration technology are providing scientists with tools to reveal life in the largest habitat on Earth. Each sighting of Magnapinna offers new clues about the natural history and behavior of this deep-sea squid. 

The deep sea is closer than you think, and human actions impact animals and ecosystems far beneath the ocean’s surface. MBARI’s research and technology are providing the independent baseline data that policymakers and the public need to weigh decisions about the future of the ocean, including protections for seamount habitats and rare species like the bigfin squid.