Schmidt Ocean Institute, April 15, 2025 reported the groundbreaking capture of the first live video footage of a colossal squid in its natural deep-sea habitat near the South Sandwich Islands. The individual filmed was a juvenile, approximately 30 centimeters long. The colossal squid (Mesonychoteuthis hamiltoni) is a truly remarkable and elusive creature inhabiting the frigid, deep waters of the Southern Ocean, primarily around Antarctica. It belongs to the family Cranchiidae, also known as glass squids, and is the only recognized member of the genus Mesonychoteuthis. Often referred to as the Antarctic cranch squid, it’s crucial not to confuse it with the giant squid (Architeuthis dux), although both hold titles as the largest invertebrates on Earth. The colossal squid is generally considered the heaviest, while the giant squid may be longer.
One of the most striking features of the colossal squid is its sheer size. While maximum total length estimates vary, with some reaching up to 14 meters (46 feet), a more likely estimate places it around 10 meters (33 feet). What truly sets it apart is its bulk; confirmed specimens have weighed in at nearly 500 kilograms (1,100 pounds), and beaks found in sperm whale stomachs suggest individuals could reach a staggering 600-700 kilograms (1,300-1,500 pounds). This makes it the heaviest known invertebrate. Unlike the giant squid, the colossal squid is thought to have a wider, more muscular body and shorter tentacles relative to its mantle length.
Adding to its mystique, the colossal squid possesses the largest eyes of any animal on the planet. These enormous orbs are estimated to have a diameter of 27 to 30 centimeters (11-12 inches), with the largest recorded reaching an astonishing 40 cm (16 inches). Such massive eyes are an adaptation to the dim, deep-sea environment, allowing them to detect faint bioluminescence from prey or the shadowy forms of predators lurking in the darkness. Their impressive vision provides a significant advantage in their deep-sea habitat.
The colossal squid is a formidable predator, primarily feeding on large fish like the Antarctic toothfish (also known as Chilean sea bass), as well as other deep-sea squid. Its eight arms and two longer tentacles are equipped with powerful swiveling hooks and serrated suckers, providing a secure grip on struggling prey. These hooks can even inflict injuries on its primary predator, the sperm whale, as evidenced by scars found on the whales. The squid’s strong, parrot-like beak efficiently slices through its prey, which is then further processed by a radula, a tongue-like organ with rows of teeth.
Living in the mesopelagic (200-1000 m) to bathypelagic (1000-4000 m) zones of the Southern Ocean, the colossal squid is an elusive creature, and much of its life cycle and behavior remain a mystery. Juveniles are found in shallower waters (0-500 m), gradually descending to greater depths as they mature. Scientists believe they are ambush predators with a slow metabolic rate, requiring relatively little food daily. Reproduction is thought to involve internal fertilization, but the specifics of mating and egg-laying are still unknown. Despite its size, the colossal squid is classified as “Least Concern” by the IUCN, likely due to its remote habitat and the lack of significant commercial fishing pressure.
