Humboldt squid

Common name This species is most often known as jumbo squid in English, but has also been called jumbo flying squid or Humboldt squid, with the last name most popular in naturalist sources. The name Humboldt refers to the Humboldt Current, off the southwestern coast of South America, where it was first collected. A general name for this species in Spanish in Latin America is . Local names for it are in Chile or in Peru. They notably rapidly flash red and white when captured, earning them the nickname (meaning 'red devil') among local fishermen in Baja California, Mexico. Taxonomy The existence of this creature was first reported to the scientific world by the Chilean priest and polymath Juan Ignacio Molina in 1782, who called it Sepia tunicata, Sepia being the type genus of cuttlefish. It was subsequently formally described as a species new to science by the French naturalist Alcide d'Orbigny, who named it Ommastrephes gigas in 1835, but an illustration was labeled Loligo gigas. Another French naturalist, Claude Gay, obtained some specimens from Chile and sent them to the Muséum national d'Histoire naturelle in Paris, where it was determined that the species did not belong in the genus Loligo either. In 1857 the Danish zoologist Japetus Steenstrup proposed the new genus Dosidicus to house the species, where it remains. The German zoologist George Pfeffer synonymized D. eschrichtii with D. gigas in 1912. The fossil species Dosidicus lomita is represented by fossils of statoliths from the Pliocene Lomita Marl of California, marking the earliest known occurrence of the genus. ==Description==

'' The Humboldt squid is the largest of the Ommastrephid squids, as some individuals may grow to in mantle length and weigh up to . Generally, the mantle (or body, which includes the fins or wings) constitutes about 56–62% of the animal's mass, the arms and tentacles about 11–15%, the head (including eyes and beak) about 10–13%, the outer skin (cuticle) 2.5–5.0%, the hepatopancreas (liver analogue) 4.2–5.6%, with the rest made up of the other inner organs. The gonads consist of 1.5–15.0% of the total mass. The gladius (the single inner 'bone') is 0.7–1.0%. Precise ratios depend on the age, sex and sizes of the individual squid. They are propelled by water ejected through a hyponome (siphon) and by two triangular fins. The Humboldt's two tentacles are elastic and can lash out with remarkable speed to grab hold of prey, holding it fast with the help of a wealth of suckers on each tentacle. Each sucker includes an inner ring of teeth. After grabbing the prey, the tentacles then retract and the prey is drawn toward a large, razor-sharp beak. ==Behavior==

Humboldt squid are carnivorous marine invertebrates that move in shoals of up to 1,200 individuals. They swim at speeds up to . Electronic tagging has shown Humboldt squid undergo diel vertical migrations, which bring them closer to the surface from dusk to dawn. Humboldt squid are thought to have a lifespan of about a year, although larger individuals may survive up to 2 years. ==Distribution and habitat==

The Humboldt squid lives at depths of in the eastern Pacific (Notably in Chile and Peru), ranging from Tierra del Fuego north to California. Recently, the squid have been found as far north as British Columbia. Although they usually prefer deeper water, between 1,000 and 1,500 squid washed up on the Long Beach Peninsula in southwest Washington in late 2004 and red algae were a speculated cause for the late 2012 beaching of an unspecified number of juvenile squid (average length ) at Monterey Bay over a 2-month period. Changes in distribution Humboldt squid are generally found in the warm Pacific waters off the Mexican coast; studies published in the early 2000s indicated an increase in northern migration. The large 1997–1998 El Niño event triggered the first sightings of Humboldt squid in Monterey Bay. Then, during the minor El Niño event of 2002, they returned to Monterey Bay in higher numbers and have been seen there year-round since then. Similar trends have been shown off the coasts of Washington, Oregon, and even Alaska, although no year-round Humboldt squid populations are in these locations. This change in migration is suggested to be due to warming waters during El Niño events, but other factors, such as a decrease in upper trophic level predators that would compete with the squid for food, could be impacting the migration shift, as well. A 2017 Chinese study found that D. gigas is affected by El Niño events in the waters off Peru. The squid populations cluster into groups less, and are thus more dispersed, during El Niño events. Additionally, during warm El Niño conditions and high water temperature the waters off Peru were less favourable for D. gigas. ==Ecology==

Prey and feeding behavior The Humboldt squid's diet consists mainly of small fish (lanternfish, in particular), crustaceans, cephalopods, and copepods. The squid uses its barbed tentacle suckers to grab its prey and slices and tears the victim's flesh with its beak and radula. They often approach prey quickly with all 10 appendages extended forward in a cone-like shape. Upon reaching striking distance, they open their eight swimming and grasping arms, and extend two long tentacles covered in sharp hooks, grabbing their prey and pulling it back toward a parrot-like beak, which can easily cause serious lacerations to human flesh. These two longer tentacles can reach full length, grab prey, and retract so fast that almost the entire event happens in one frame of a normal-speed video camera. Each of the squid's suckers is ringed with sharp teeth, and the beak can tear flesh, although they are believed to lack the jaw strength to crack heavy bone. This behavior may account for a large proportion of their rapid growth. An investigation of the stomach contents of over 2,000 squid caught outside of the Exclusive Economic Zone off the coasts of Chile found that cannibalism was likely the most important source of food. Over half had the beaks of D. gigas in their stomachs, and D. gigas was the most common prey item. The researchers do note, however, that squid jigged in the light field around the survey vessel showed much more cannibalism. However, research conducted between 2007 and 2011 indicates this species does engage in cooperative hunting. Reproduction Females lay gelatinous egg masses that are almost entirely transparent and float freely in the water column. The size of the egg mass correlates with the size of the female that laid it; large females can lay egg masses up to in diameter, while smaller females lay egg masses about in diameter. Records of egg masses are extremely sparse because they are rarely encountered by humans, but from the few masses found to date, the egg masses seem to contain anywhere from 5,000 to 4.1 million eggs, depending on size. ==Relationship to humans==

Aggression toward humans Numerous accounts have the squid attacking fishermen and divers. Their coloring and aggressive reputation have earned them the nickname diablos rojos (red devils) from fishermen off the coast of Mexico, as they flash red and white when struggling on a line. In circumstances where these animals are not feeding or being hunted, they exhibit curious and intelligent behavior. Recent footage of shoals of these animals demonstrates a tendency to meet unfamiliar objects aggressively. Having risen to depths of below the surface to feed (up from their typical diving depth, beyond the range of human diving), they have attacked deep-sea cameras and rendered them inoperable. Humboldt squid have also been observed engaging in swarm behavior when met by the lights of submersibles, suggesting that they may follow or are attracted to light. Reports of recreational scuba divers being attacked by Humboldt squid have been confirmed. Fisheries Commercially, this species has been caught to serve the European market (mainly Spain, Italy, France, and Ireland), Russia, China, Japan, Southeast Asia, and increasingly North and South American markets. It is the most popular squid in the world; as of 2019 a third of all squid hunted is this species. The method used by both artisanal fishermen as well as more industrial operations to catch the squid is known as jigging. It is done by handlining by artisanal fishermen, or by using mechanical jiggers. Jigging involves constantly jerking the line up and down to simulate prey; a reel with an elliptical or oval-shaped hub helps with this. Squid jigging is done at night, using bright overhead lights from the fishing boats which reflect brightly off the jigs and plankton in the seawater, luring the squid toward the surface to feed. They seem to prefer striking at the jigs from adjacent shadowed areas, especially the shade under the hull of the boat. in Valparaiso, Chile. The remarkable size of the squid giant axon and squid giant synapse possessed by the Humboldt squid made it ideal for manipulative work in the laboratory. A more recent study, however, provided empirical and theoretical evidence that the squid metabolism was unaffected by ocean acidification. In popular media The Humboldt squid was featured in the final episode of the 2009 BBC's Last Chance to See with Stephen Fry and Mark Carwardine. The episode was about blue whales, but the presenters interviewed fishermen who talked about the "exploding" diablo rojo population in the Sea of Cortez and human attacks, and showed a squid trying to take a bite of a protectively clad forearm. In 2016 the squid featured in various television shows. Man Eating Super Squid: A Monster Invasion on the National Geographic Wild channel explored various attacks by Humboldt squid in Mexico. In the show, the squid is referred to as a real-life kraken and as "a global threat". The second show was River Monsters: Devil of the Deep, where show host Jeremy Wade talks to fishermen allegedly attacked by the squid in the Sea of Cortez, and then catches the animals off the coast of Peru. In the British , mail-clad divers plan to capture a Humboldt squid by hand in the Pacific Ocean, but are prevented from doing so due to bad weather. In BBC Earth's Blue Planet II the squid's cannibalistic pack hunting was captured on film for the first time. ==See also==