Taningia danae, the Dana octopus squid, is a species of squid in the family Octopoteuthidae, the octopus squids. It is one of the largest known squid species, and it has one of the largest photophores (light organs) known in any organism, useful in the deep-sea environments that the species inhabits.
Discovery The possible (but unconfirmed) first specimen of this species was collected in 1769, when Joseph Banks, member of Captain Cook’s first voyage, spotted a massive "cuttlefish" floating in the South Pacific, off the coast of Chile. Seabirds had already damaged it, and most of the remaining carcass was prepared into a meal which Banks described as "one of the best soups [he] ever ate". However, he made sure to preserve an arm, some entrails, and the buccal mass including the beak, which would eventually enter John Hunter's collection in London; the surviving buccal mass (apparently prepared by John Hunter himself) is still part of the Hunterian Museum’s collection to this day. These specimens received multiple scientific names over the years, such as Sepia unguiculata, Enoploteuthis molina, Enoploteuthis cooki, and Cucioteuthis unguiculatus, though these names cannot be definitively linked to the modern conception of T. danae, and the species assigned to Cucioteuthis are considered nomina dubia. In 1931 the name Taningia danae was coined, after the Danish fisheries biologist Åge Vedel Tåning (1890–1958), and the Danish ship Dana, which collected a more complete specimen that became the holotype of this species. The taxonomic situation of Octopoteuthids in general require further revision.
Description
Typical of octopus squid, T. danae is characterized by their tentacles that do not continue growing past the paralarval stage, giving them eight arms in adulthood like an octopus. Taningia is separated from Octopoteuthis by adults possessing a large photophore on both tips of the second pair of arms (arm pair II; counted from the dorsal surface), which along with the ink sac light organ are the only known photophores on the body. The arm photophores are some of the largest such organs known in the animal kingdom, being comparable in size to fists or lemons. These organs possess eyelid-like skin flaps which can conceal the light organs when needed. Each arm pair bears two rows of hooks covered by a hood of tissue that can unsheathe them when needed. This species is traditionally thought to be the only one within the genus and cosmopolitan, but additional species have at times been recognized; this would render Taningia danae as traditionally known a species complex. When recognizing different species of Taningia, T. danae can be distinguished through the blunt shape of the part of the funnel-locking apparatus facing the mouth, arm-hooks only possessing a single tip or point, the male not having enlarged hooks on the base of his arm pair I, the arms being 25-46% mantle length, the skin and funnel opening being smooth (without any accessory structures), along with specific characters of the beak. The muscular fins account for a large part of the animal's mass; around 61% of the total mass being the fins, 23% being the head and arms combined, and the mantle being 14%. The entire reproductive system makes up half of the total mass of the viscera, but the most massive individual organs are each of the gills, which are 29% of the visceral mass. The Dana octopus squid reaches a mantle length of up to 1.7 m (5.6 ft) and total length of 2.3 m (7.5 ft). The largest known specimen, a mature female, weighed 161.4 kg (356 lb).
Biology Taningia danae is considered an oceanic, mesopelagic species that likely spawns in deep waters, although its biology remains largely undocumented. Most of the specimens studied globally - particularly the larger individuals - have been recovered from the guts of its predators, primarily sperm whales, but also sharks, lancetfishes, tunas, wandering albatrosses, and elephant seals. Remains of T. danae have sometimes been found washed ashore on beaches. In 2008, a mantle of T. danae was discovered by students in Bermuda's Grape Bay, while tentacle remnants were found farther along the shore. In early 2013, a 54 kg (119 lb) specimen with a length (excluding arms) of 103 cm (3.38 ft) was trawled at a depth of 240 m (790 ft) off the coast of Estaca de Bares, Galicia, Spain. It was loaned to the Spanish Institute of Oceanography. A largely-intact 140 kg (310 lb) specimen was found floating around 100km off the South Australian coast and sent to Flinders University in Adelaide where it was dissected in July 2024. The Dana octopus squid is thought to be extremely abundant in some regions, accounting for over 80% of the weight of sperm-whale-stomach contents off Iberia, and 97% of sampled sperm whales in the Tasman Sea had consumed this octopus squid.
Behavior Like other mesopelagic animals, Taningia spp. undergo diel migration, though these squid only migrate for short distances compared to other species (from 900–600 m (3,000–2,000 ft) to 500–240 m (1,640–790 ft) depth). In 2005, a Japanese research team headed by Tsunemi Kubodera managed to film a purported T. danae in its natural habitat for the first time. The video footage, shot in deep water off Chichi-jima in the northern Pacific Ocean, shows that contrary to earlier assumptions, Taningia is an "aggressive and tenacious predator" and a powerful swimmer, capable of quickly changing direction by flexing its mantle, along with swimming forward and backwards by flapping its muscular fins; swimming by fin undulation has the advantage of providing consistent motion compared to the pump-pause cycle of jet propulsion. This method has been compared to the swimming style of rays, and it has been estimated that the observed octopus squid reached speeds of around 2–2.5 m (6 ft 7 in – 8 ft 2 in) per second. However, specimens found in Japanese seas may be of another species of Taningia; Taningia rubea is endemic to the seas around Japan and can be easily distinguished by its longer "tail". Taningia danae is bioluminescent, akin to other octopoteuthids and squid families. Black, eyelid-like membranes control the photophore's light emissions; these can be made to "blink", producing a flash of light.
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