A record-setting discovery
In April 2019, the Five Deeps Expedition captured footage of an octopus nearly 7,000 meters (22,965 feet) below the surface of the Indian Ocean. This observation, made in the Java Trench, shattered the previous reliable sighting record for any cephalopod by more than 1,800 meters. The creature belongs to the genus Grimpoteuthis, commonly known as the Dumbo octopus. This discovery provided the first irrefutable evidence of a cephalopod living in the hadal zone, the deepest region of the ocean below 6,000 meters. While this specific record occurred in the Indian Ocean, species of Grimpoteuthis have a worldwide distribution, with specimens found in the abyssal zones off the coast of the Philippines.
The images were taken by autonomous "landers," instrument frames with cameras dropped from the research ship. The expedition's chief scientist, Dr. Alan Jamieson, noted two sightings: one at 5,760 meters and the record-breaker at 6,957 meters. The individuals observed were relatively large for Dumbo octopuses, measuring 35 and 43 centimeters (14 and 17 inches) long. Scientists believe it may be a new, undocumented species of Grimpoteuthis.
Life under extreme pressure
Surviving at 7,000 meters requires extreme biological adaptations. The hydrostatic pressure at this depth is immense, exceeding 10,000 pounds per square inch (PSI), or nearly 700 times the pressure at sea level. To cope, the Dumbo octopus has a soft, semi-gelatinous body that lacks the rigid structures that would collapse under such force. An internal cartilaginous shell provides some shape without compromising flexibility.
Most octopuses use energy-intensive jet propulsion, the Dumbo octopus primarily moves by flapping its prominent, ear-like fins. It uses its webbed arms for steering, hovering just above the seafloor. This method of locomotion is energy-efficient, a trait for the food-scarce abyss. Its diet consists of small crustaceans, bivalves, snails, and bristle worms that it finds on or near the ocean bottom. Having a degenerated beak, it swallows its prey whole.
Life in total darkness has influenced its defenses. The Dumbo octopus has no ink sac, which would be useless in an environment without light. It has few natural predators at these depths, though in the shallower parts of its range it can be preyed upon by deep-diving sharks and marine mammals. Its reproductive strategy is also adapted for a solitary existence. Females carry eggs at various stages of development and can store sperm packets from a male encounter, allowing them to fertilize eggs and lay them on hard surfaces when conditions are suitable.