Colossal squid

The beak of a colossal squid

Little is known about the behavior of this creature, but it is believed to feed on prey such as chaetognatha, large fish such as the Patagonian toothfish, and smaller squid in the deep ocean using bioluminescence.[11] A recent study by Remeslo, Yakushev and Laptikhovsky revealed that Antarctic toothfish make up a significant part of the colossal squid's diet; of the 8,000 toothfish brought aboard trawlers between 2011 and 2014, seventy-one showed clear signs of attack by colossal squid.[24] A study in Prydz Bay region of Antarctica found squid remains in a female colossal squid's stomach, suggesting the possibility of cannibalism within this species.[25]

The colossal squid is thought to have a very slow metabolic rate, needing only around 30 grams (1.1 oz) of prey daily for an adult with a mass of 500 kilograms (1,100 lb).[26] Estimates of its energy requirements suggest it is a slow-moving ambush predator, using its large eyes primarily for prey-detection rather than engaging in active hunting.[26][13]

Many sperm whales have scars on their backs, believed to be caused by the hooks of colossal squid. Colossal squid are a major prey item for sperm whales in the Antarctic; 14% of the squid beaks found in the stomachs of these sperm whales are those of the colossal squid, which indicates that colossal squid make up 77% of the biomass consumed by these whales.[27] Many other animals also feed on colossal squid, including beaked whales (such as the southern bottlenose whale), pilot whales, southern elephant seals, Patagonian toothfish, sleeper sharks (Somniosus antarcticus), and albatrosses (e.g., the wandering and sooty albatrosses).[4] However, beaks from mature adults have only been recovered from large predators (i.e. sperm whales and sleeper sharks), while the other predators only eat juveniles or young adults.[28]

Little is known about the colossal squid’s reproductive cycle although the colossal squid does have two distinct sexes. Many species of squid, however, develop gender-specific organs as they age and develop. [29]. The adult female colossal squid has been discovered in much shallower waters which likely implies that females spawn in shallower waters than their normal depth [30]. Additionally, the colossal squid has a high possible fecundity reaching over 4.2 million oocytes which is quite unique compared to other squids in such cold waters [31].

Unlike swordfish and other large pelagic species, the colossal squid (along with the giant squid) has eyes that are nearly 2-3 times the diameter of their deepsea counterparts. Further research suggests that colossal squid are able to see bioluminescence generated by large predators that disrupt plankton when they move. Additionally, this supports the idea that colossal squid are ambush predators [12].

The species was first discovered in the form of two arm crowns found in the stomach of a sperm whale in the winter of 1924-1925.[14] This species, then named Mesonychoteuthis hamiltoni, was formally described by Guy Coburn Robson 1925.[14]

In 1981, a Russian trawler in the Ross Sea, off the coast of Antarctica, caught a large squid with a total length of over 4 m (13 ft), which was later identified as an immature female of M. hamiltoni.[15] This is a significant discovery for it would not be until 2003, that another full individual was discovered. In 2003, a complete specimen of a subadult female was found near the surface with a total length of 6 m (20 ft) and a mantle length of 2.5 m (8 ft 2 in).[16] In 2005, the first full alive specimen was captured at a depth of 1,625 m (5,331 ft) while taking a toothfish from a longline off South Georgia Island.[32] Although the mantle was not brought aboard, its length was estimated at over 2.5 m (8 ft 2 in), and the tentacles measured 2.3 m (7 ft 7 in).[32] The animal is thought to have weighed between 150 and 200 kg (330 and 440 lb).[32]

This specimen, caught in early 2007, is the largest cephalopod ever recorded. Here it is shown alive during capture, with the delicate red skin still intact and the mantle characteristically inflated.

The largest recorded specimen was a female, which are thought to be larger than males, captured in February of 2007 by a New Zealand fishing boat in the Ross Sea off of Antarctica.[21] The squid was close to dead when it was captured and subsequently was taken back to New Zealand for scientific study.[33]  The specimen was initially estimated to measure about 10 meters in total length and weigh about 450 kg.[33] The squid turned out to actually weigh 495 kg.[17]

Thawing and dissection of the specimen took place at the Museum of New Zealand Te Papa Tongarewa.[34] AUT biologist Steve O'Shea, Tsunemi Kubodera, and AUT biologist Kat Bolstad were invited to the museum to aid in the process.[34] Media reports suggested scientists at the museum were considering using a giant microwave to defrost the squid because thawing it at room temperature would take several days and it would likely begin to decompose on the outside while the core remained frozen.[35] However, they later opted for the more conventional approach of thawing the specimen in a bath of salt water.[36] After thawing, it was found that the specimen was 495 kg only 2.5 m, probably because the tentacles shrunk once the squid was dead.[17]

Parts of the specimen have been examined:

• The beak is considerably smaller than some found in the stomachs of sperm whales,[37][38] suggesting other colossal squid are much larger than this one.[37][38]
• The eye is 27 cm (11 in) wide, with a lens 12 cm (4.7 in) across. This is the largest eye of any known animal.[20] These measurements are of the partly collapsed specimen; alive, the eye was probably 30[21] to 40 cm (12 to 16 in) across.[39]
• Inspection of the specimen with an endoscope revealed ovaries containing thousands of eggs.[21]

The specimen on display at the Museum of New Zealand Te Papa Tongarewa

The Museum of New Zealand Te Papa Tongarewa began displaying this specimen in an exhibition that opened on December 13, 2008; however the exhibition was closed in 2018 and slated to return in 2019.[18]

In August 2014, Te Papa received a second colossal squid, captured in early 2014.[19] The specimen was also female, was 3.5 metres (11 ft) long and weighed approximately 350 kg (770 lb).[40]