| Taningia danae | |
|---|---|
 | |
| Taningiacf. danae, Hutchison Seamounts, offHawai'i, 2015 | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Order: | Oegopsida |
| Family: | Octopoteuthidae |
| Genus: | Taningia |
| Species: | T. danae |
| Binomial name | |
| Taningia danae | |
| Synonyms | |
Taningia danae, theDana octopus squid, is a species ofsquid in the familyOctopoteuthidae, the octopus squids. It is one of thelargest known squid species, and it has one of the largestphotophores (light organs) known in any organism, useful in thedeep-sea environments that the species inhabits.
The possible (but unconfirmed) first specimen of this species was collected in 1769, whenJoseph Banks, member ofCaptain Cook’s first voyage, spotted a massive "cuttlefish" floating in the South Pacific, off the coast ofChile.Seabirds had already damaged it, and most of the remaining carcass wasprepared into a meal which Banks described as "one of the bestsoups [he] ever ate". However, he made sure to preserve anarm, someentrails, and the buccal mass including thebeak, which would eventually enterJohn Hunter's collection in London; the surviving buccal mass (apparently prepared by John Hunter himself) is still part of theHunterian Museum’s collection to this day. These specimens received multiplescientific names over the years, such asSepia unguiculata,Enoploteuthis molina,Enoploteuthis cooki, andCucioteuthis unguiculatus, though these names cannot be definitively linked to the modern conception ofT. danae, and the species assigned toCucioteuthis are considerednomina dubia.[3] In1931 the nameTaningia danae was coined, after theDanishfisheries biologistÅge Vedel Tåning (1890–1958), and the Danish shipDana, which collected a more complete specimen that became theholotype of this species.[4][5][6] The taxonomic situation of Octopoteuthids in general require further revision.[3][7]
Typical of octopus squid,T. danae ischaracterized by their tentacles that do not continue growing past theparalarval stage, giving them eight arms in adulthood like anoctopus.[8][9]Taningia is separated fromOctopoteuthis by adults possessing a largephotophore on both tips of the second pair of arms (arm pair II; counted from thedorsal surface), which along with theink sac light organ are the only known photophores on the body.[a] The arm photophores are some of the largest such organs known in the animal kingdom, being comparable in size tofists orlemons.[10] These organs possesseyelid-like skin flaps which can conceal the light organs when needed.[3] Each arm pair bears two rows of hooks covered by a hood of tissue that can unsheathe them when needed.[8][11]
This species is traditionally thought to be theonly one within the genus andcosmopolitan, but additional species have at times been recognized; this would renderTaningia danae as traditionally known aspecies complex. When recognizing different species ofTaningia,T. danae can bedistinguished through the blunt shape of the part of thefunnel-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 andfunnel opening being smooth (without anyaccessory structures), along with specific characters of the beak.[7]
The muscularfins account for a large part of the animal'smass; around 61% of the total mass being the fins, 23% being the head and arms combined, and themantle being 14%. The entirereproductive system makes up half of the total mass of theviscera, but the most massive individual organs are each of thegills, which are 29% of the visceral mass.[7]
The Dana octopus squid reaches amantle length of up to 1.7 m (5.6 ft)[12] and total length of 2.3 m (7.5 ft).[13] The largest known specimen, a mature female, weighed 161.4 kg (356 lb).[8][b]
Taningia danae is considered an oceanic,mesopelagic species that likely spawns in deep waters, although its biology remains largely undocumented.[3] Most of the specimens studied globally - particularly the larger individuals - have been recovered from the guts of its predators, primarilysperm whales, but alsosharks,lancetfishes,tunas,wandering albatrosses, andelephant seals.[3] Remains ofT. danae have sometimes been found washed ashore on beaches. In 2008, a mantle ofT. danae was discovered by students inBermuda'sGrape Bay, whiletentacle remnants were found farther along the shore.[14]
In early 2013, a 54 kg (119 lb) specimen with a length (excluding arms) of 103 cm (3.38 ft) wastrawled at a depth of 240 m (790 ft) off the coast ofEstaca de Bares,Galicia,Spain. It was loaned to theSpanish Institute of Oceanography.[15] A largely-intact 140 kg (310 lb) specimen was found floating around 100km off the South Australian coast and sent toFlinders University in Adelaide where it was dissected in July 2024.[16]
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 offIberia, and 97% of sampled sperm whales in theTasman Sea had consumed this octopus squid.[3]
Like othermesopelagic animals,Taningia spp. undergodiel 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).[13]
In 2005, aJapanese research team headed byTsunemi Kubodera managed to film a purportedT. danae in itsnatural habitat for the first time. The video footage, shot in deep water offChichi-jima in the northernPacific 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 ofjet propulsion. This method has been compared to the swimming style ofrays, 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.[13] However, specimens found in Japanese seas may be of another species ofTaningia;Taningia rubea isendemic to the seas around Japan and can be easily distinguished by its longer "tail".[7]
Taningia danae isbioluminescent, akin to other octopoteuthids and squid families. Black, eyelid-likemembranes control the photophore's light emissions; these can be made to "blink", producing a flash of light.[5]
The 2005 video showsT. danae emitting blinding flashes of light from its arm photophores as it attacks its prey (in this instance, abaited line). It is believed that this squid uses the bright flashes todisorient potential prey, as well as potentiallygauging its distance to prey, facilitating capture.[13]T. danae bioluminescence has also been suggested to be adefense mechanism; juveniles of this species have been observed moving rapidly in the direction of potential predators, as if hunting, which are probably attempts to disorient and startle the threat with a mock-attack.[17]
The light-organs, capable of producing different flash-patterns, may serve as a method tocommunicate, perhaps incourtship oraggressive displays related toterritory; an observed squid made long and short light-emissions in response to a double-flashlight array mounted to the camera-rig (which resembledTaningia's pair of light-organs). These responses may have been attempts of communication toward the rig as the observed squid did not seem aggressive. Due to a lack of response by the light-array, the squid moved on.[13]
In 2012,T. danae was filmed twice more during a search for thegiant squid for theDiscovery Channel Special,Monster Squid: The Giant is real.[18][clarification needed]
Taningia danae appears to occupy a hightrophic level, at least in theSouthern Ocean ecosystem.15N ratios showed that this squid is a top predator.[19][clarification needed]Stable isotope analysis of specimens from theGreat Australian Bight suggests they primarily feed on deep-sea fishes and small squids.Fatty acid profiles of the contents ofT. danae'sdigestive gland were found to be similar to wholehomogenized samples of deep-sea fishes likeElectrona carlsbergi,Epigonus lenimen, andLepidorhynchus denticulatus, supporting the hypothesis that these fishes are prey items.[20] Analysis of stomach contents from specimens retrieved off the coast of Spain has found blue whiting (Micromesistius poutassou) vertebrae,Gonatus sp. tentacle-hooks, andintegument ofcrustaceans.[21]
Theircarbon isotope ratios indicate that they likely live in the Southern Ocean, but may travel tocontinental shelf-slope environments like the Great Australian Bight possibly during seasonalupwelling events. The presence of copepod fatty acidbiomarkers inT. danae tissues further suggests they are part of acopepod-myctophid-squid food chain, common in the Southern Ocean.T. danae appears to function as a link between deep-sea and shelf-slope environments, contributing to the transport of nutrients and energy between these different marine ecosystems.[20]
T. danae muscletissues contain high levels ofessential fatty acids EPA (20:5ω3) and DHA (22:6ω3), making them a nutrient source for predators such assperm whales, seabirds, and seals. WhileT. danae has a relatively lowenergy density per gram (approximately 2.25kJ/g) compared to other Southern Ocean fish and squid species, their large body size means individual specimens contain substantial energy. The whole-body energy content of a largeT. danae individual (161 kg) can reach up to 362,250 kJ, making it one of the mostcalorically rich prey items in the Southern Ocean and an efficient food source for large predators like sperm whales.[20]
This species is a known prey item of the sperm whale, a prolific predator of squid.[22][23][24] Other predators include thepygmy sperm whale,[25][26]beaked whales such as theCuvier's andsouthern bottlenose whales,[27][28][29] dolphins such as theshort-finned pilot whale,Risso's andFraser's dolphins,[27][30][31]northern elephant seals,[32]ground sharks such as thetiger,blue, andscalloped hammerhead sharks,[33][3]dogfish such as thePortuguese dogfish andsleeper sharks,[33][34][35][36]swordfish,[37] andtube-nosed seabirds whichscavenge dead squid on the surface, such as theBulwer's petrel, along with species ofalbatross like theblack-browed,Laysan, andwandering albatrosses.[38][39][40]
Taningia danae employs a unique reproductive strategy known as spermatangium implantation, facilitated by the presence of an extendable terminal organ/penis (unlike thehectocotylus of many other cephalopods).[21] During mating, the male uses either its beak or arm hooks to make incisions in the female's tissue, into which it implantsspermatophores - packets containing sperm. While spermatangium implantation is observed in several squid species,T. danae is unusual in its use of physical incisions for implantation. In most other squids, females possess specialized structures or receptacles for receiving spermatophores, makingT. danae’s method notably distinct.[41][7] These incisions, typically 30–65 mm (1.2–2.6 in) in length, are usually found in the head, neck, and inner mantle tissues, particularly around the "nuchal" region and collar musculature. Unlike many other cephalopods,T. danae implants their spermatangia deep within muscle layers rather than attaching them externally. Some spermatangia may implant autonomously, likely aided by enzymes or filament-like structures that help them penetrate the tissue. Due to the physical trauma involved in this process, mating may pose a risk of injury to the male, and there is speculation that females may sometimes engage incannibalism.[41]
The arm-hooks start developing after theparalarva reaches 5 mm (0.20 in) ML; a single photophore on the ink sac also develops at this size,[8] which is thought to be acounter-illumination mechanism in the relatively transparent juveniles.[3] The paralarvae have robust tentacular stalks which disappear at 38 mm (1.5 in) ML, leaving the adult squid with eight arms.[8] A post-larval juvenile 55.6 mm (2.19 in) ML was captured off the coast ofAlgeria, being the first Mediterranean record of this species.[42] Females begin to sexually mature at 200–400 mm (7.9–15.7 in) ML, with the smallest specimen known to havespawned being 882 mm (34.7 in) ML.[7]
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