Rarely-Seen Seven-Arm ‘Blob’ Octopus Filmed by Underwater Camera

08 Dec 2025, 14:07 by Pesala Bandara · Peta Pixel

A rarely seen seven-arm octopus known as “the blob octopus” was captured on camera 2,300 feet below the surface in remarkable deep-sea footage.

The species — formally known as the seven-arm octopus (Haliphron atlanticus) — was recorded by the remotely operated vehicle Ventana, operated by the team at the Monterey Bay Aquarium Research Institute (MBARI). According to MBARI, the encounter occurred during a recent expedition in Monterey Bay and marks only the fourth time the organisation has observed this species in nearly four decades of deep-sea exploration.

According to MBARI, Senior Scientist Steven Haddock and members of the institute’s Biodiversity and Biooptics Team came across the octopus at roughly 2,300 feet during routine survey work. Using a 4K camera system developed by MBARI engineers for deep-sea missions, the team documented the animal’s appearance and behaviour in high-resolution detail.

MBARI describes the animal as a “rarely seen giant” of the ocean’s twilight zone, and its latest footage adds to the limited but growing record of one of the deep sea’s most elusive species. Female seven-arm octopuses can grow to considerable sizes, reaching up to 165 pounds, while males are far smaller, often no more than eight inches long. Despite its name, the species has eight arms like other octopuses, according to MBARI. In males, one arm — the reproductive hectocotylus — is kept tucked into a sac beneath the right eye, creating the appearance of having only seven.

The octopus was holding a crimson helmet jelly (Periphylla periphylla) in the footage captured last month, consistent with past MBARI findings that Haliphron atlanticus preys on gelatinous animals. Previous research by Haddock and MBARI collaborator Henk-Jan Hoving first demonstrated that this species feeds on jellies — a behaviour that museum specimen analysis later reinforced. Although gelatinous prey is relatively low in nutritional value, it is abundant in the deep ocean and sustains a range of large predators.

“Using a 4K camera specially developed by MBARI engineers for deep-sea exploration, the team collected detailed observations of the animal’s appearance and behavior,” MBARI writes on YouTube. “This extraordinary octopus was clutching a crimson red helmet jelly (Periphylla periphylla). This new sighting underscores the complexity of deep-sea food webs and their surprising connections.”