Vampire Squid

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(Redirected from Vampyromorphida)
vampire squid
vampire squid
Scientific classification
Kingdom:Animalia
Phylum:Mollusca
Class:Cephalopoda
Subclass:Coleoidea
Superorder:Octopodiformes
Order:Vampyromorphida
Pickford, 1939
Family:Vampyroteuthidae
Thiele, 1915
Genus:Vampyroteuthis
Chun, 1903
Species:V. infernalis
Binomial name
Vampyroteuthis infernalis
Chun, 1903

The vampire squid (Vampyroteuthis infernalis, lit. "vampire squid from hell") is a small, deep-sea cirrate (finned) cephalopod found throughout the temperate and tropical oceans of the world. Unique retractile sensory filaments justify the vampire squid's placement in its own order: Vampyromorphida (formerly Vampyromorpha), sharing similarities with both squid and octopuses. As a phylogenetic relic it is the only surviving member of its order, first described and mistakenly identified as an octopus in 1903 by German teuthologist Carl Chun.

Contents

Physical description

At a maximum 30 cm (1 foot) in total length, the vampire squid is of no threat to humans. Its 15 cm (6 inch) gelatinous body appears velvety jet-black, red, purple or brown, depending on location and lighting conditions. A webbing of skin connects its eight arms, each lined with rows of fleshy spines or cirri. Only the distal half (farthest from the body) of the arms have suckers. Its limpid, globular eyes—which appear red or blue, also depending on lighting—are proportionately the largest in the animal kingdom at 2.5 cm (1 inch) in diameter.

Mature adults have a pair of ear-like fins projecting from the lateral sides of the mantle. These fins serve as the adult's primary means of propulsion: vampire squid are said to "fly" through the water by way of flapping their fins. Their powerful beak-like jaws are as white as ivory. Within the webbing are two pouches wherein the tactile velar filaments are concealed. The filaments are analogous to a true squid's tentacles, extending well past the arms.

The vampire squid is covered entirely in light-producing organs called photophores. The animal has great control over the organs, capable of producing disorienting flashes of light for fractions of a second to several minutes in duration. The intensity and size of the photophores can also be modulated. Appearing as small white discs, the photophores are larger and more complex at the tips of the arms and at the base of the two fins, but are absent from the underside of the caped arms.

The chromatophores (pigment organs) common to most cephalopods are poorly developed in vampire squid. While this means the animal is not capable of changing their skin colour in the dramatic fashion of shallow-dwelling cephalopods, such trickery is not needed at the pitch black depths in which it lives.

Habitat and adaptations

The vampire squid is an extreme example of a deep-sea cephalopod, thought to reside at aphotic (lightless) depths from 600-900 metres (2,000-3,000 feet) or more. Within this region of the world's oceans is a discrete habitat known as the oxygen minimum zone (OMZ). Within the OMZ oxygen saturation is too low to support aerobic metabolism in most higher organisms. Nonetheless, the vampire squid is able to live and breathe normally in the OMZ at oxygen saturations as low as 3%; a feat no other cephalopod—and few other animals—can claim.

In order to cope with life in the suffocating depths, vampire squid have developed several radical adaptations. Of all deep-sea cephalopods, their mass-specific metabolic rate is the lowest. Their blue blood's hemocyanin binds and transports oxygen most efficiently, aided by gills with especially large surface area. The animals have weak musculature but maintain agility and buoyancy with little effort thanks to sophisticated statocysts (balancing organs akin to a human's inner ear) and ammonium-rich gelatinous tissues closely matching the density of the surrounding seawater.

At the shallower end of the vampire squid's vertical range, the view from below is like the sky at twilight: The highly sensitive eyes of deepwater denizens are able to distinguish the silhouettes of other animals moving overhead. To combat this, the vampire squid generates its own bluish light (bioluminescence) in a strategy called counterillumination: The light diffuses the animal's silhouette, effectively "cloaking" its presence from the watchful eyes below. Its own large eyes detect even the faintest of gleams. A pair of photoreceptors are located atop its head, perhaps alerting the animal to movements above.

Like other deep-sea cephalopods, vampire squid lack ink sacs. If threatened, instead of ink, a sticky cloud of bioluminescent mucus containing innumerable orbs of blue light is ejected from the arm tips. This luminous barrage, which may last nearly 10 minutes, is presumably meant to daze would-be predators and allow the vampire squid to disappear into the blackness without the need to swim far. The display is made only if the animal is very agitated; regenerating the mucus is costly.

Development

Few specifics are known regarding the ontogeny of the vampire squid. Their development progresses through three morphologic forms: the very young animals have a single pair of fins, an intermediate form has two pairs, and the mature form again has one. As the animals grow and their surface area to volume ratio drops, the fins are resized and repositioned in order to maximize gait efficiency. Whereas the young propel themselves primarily by jet propulsion, mature adults find flapping their fins to be the most efficient means. This unique ontogeny caused confusion in the past, with the varying forms identified as several species in distinct families.

If hypotheses may be drawn from knowledge of other deep-sea cephalopods, the vampire squid likely reproduces slowly by way of a small number of large eggs. Growth is slow as nutrients are not abundant at depths frequented by the animals. The vastness of their habitat and its sparse population make procreative encounters a fortuitous event. The female may store a male's hydraulically implanted spermatophore (a sort of tapered, cylindrical satchel of sperm) for long periods before she is ready to fertilize her eggs. Once she does, she may need to brood over them for up to 400 days before they hatch. The female will not eat towards this culmination and dies shortly thereafter.

Hatchlings are c. 8 mm in length and are well-developed miniatures of the adults, with some differences. Their arms lack webbing, their eyes are smaller and their velar filaments are not fully formed. The hatchlings are transparent and survive on a generous internal yolk for an unknown period before they begin to actively feed. The smaller animals frequent much deeper waters, perhaps feeding on marine snow (falling organic detritus).

Behaviour

What behavioural data known has been gleaned from ephemeral encounters with ROVs; animals are often damaged during capture and survive for no more than about two months in aquaria. An artificial environment makes reliable observation of non-defensive behaviour difficult.

With their long velar filaments deployed, vampire squid have been observed drifting along in the deep, black ocean currents. If the filaments contact an entity, or if vibrations impinge upon them, the animals investigate with rapid acrobatic movements. They are capable of swimming at speeds equivalent to two body lengths per second, with an acceleration time of five seconds. However, their weak muscles limit stamina considerably.

Unlike their deep-sea relatives, cephalopods living in more hospitable climes can afford to expend energy in protracted flight. Vampire squid must use innovative predator avoidance tactics in order to conserve energy. Their aforementioned bioluminescent "fireworks" are combined with the writhing of glowing arms, erratic movements and escape trajectories, making it difficult for a predator to home in.

In a threat response called "pumpkin posture," the vampire squid inverts its caped arms back over the body, presenting an ostensibly larger form covered in unappetizing spines. The underside of the cape is heavily pigmented, masking most of the body's photophores. The glowing arm tips are clustered together far above the animal's head, diverting attack away from critical areas. If a predator were to bite off an arm tip, the vampire squid can regenerate it.

Copepods, prawns and cnidarians have all been reported as prey of vampire squid. Little else is known regarding their feeding habits, but considering their environment, a fussy palate is unlikely. Vampire squid have been found among the stomach contents of large deepwater fish, deep diving whales and pinnipeds such as sea lions.

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References

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