Vampire squid

Vampire Squid
Adult vampire squid
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	Coleoidea
Superorder:	Octopodiformes
Order:	Vampyromorphida
Suborder:	Vampyromorphina
Family:	Vampyroteuthidae
Genus:	Vampyroteuthis Chun, 1903
Species:	V. infernalis
Binomial name
Vampyroteuthis infernalis Chun, 1903
Synonyms
Cirroteuthis macrope Berry, 1911 Vampyroteuthis macrope (Berry, 1911) Melanoteuthis lucens Joubin, 1912 Watasella nigra Sasaki, 1920 Danateuthis schmidti Joubin, 1929 Hansenoteuthis lucens Joubin, 1929 Melanoteuthis schmidti Joubin, 1929 Melanoteuthis beebei Robson, 1929 Retroteuthis pacifica Joubin, 1929 Melanoteuthis anderseni Joubin, 1931

The vampire squid (Vampyroteuthis infernalis, lit. "vampire squid from 'Hell'") is a small, deep-sea 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), which shares similarities with both squid and octopuses. As a phylogenetic relict it is the only known surviving member of its order, first described and originally classified as an octopus in 1903 by German teuthologist Carl Chun, but later assigned to a new order together with several extinct taxa.

Physical description

The Vampire Squid reaches a maximum total length of around 30 cm (1 ft). Its 15 cm (6 inch) gelatinous body varies in color between velvety jet-black and pale reddish, depending on location and lighting conditions. A webbing of skin connects its eight arms, each lined with rows of fleshy spines or cirri; the inside of this "cloak" is black. Only the distal half (farthest from the body) of the arms have suckers. Its limpid, globular eyes, which appear red or blue, depending on lighting, are proportionately the largest in the animal kingdom at 2.5 cm (1 inch) in diameter.^{[citation needed]} The animal's dark color, cloak-like webbing, and red eyes are what gave the Vampire Squid its name.^[1]

Dorsal view

Oral view

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 "fly" through the water by flapping their fins. Their beak-like jaws are white. 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; however, they are a different arm pair than the squid's tentacles. Instead, the filaments are the same pair that were lost by the ancestral octopuses.

The Vampire Squid is almost entirely covered 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. Two larger white areas on top of the head were initially believed to also be photophores, but have turned out to be photoreceptors.

The chromatophores (pigment organs) common to most cephalopods are poorly developed in the Vampire Squid. While this means the animal is not capable of changing its skin colour in the dramatic fashion of shallow-dwelling cephalopods, such trickery is not needed at the lightless depths where 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.

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 more efficiently than in other cephalopods,^[2] 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)^[3] 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 on top of its head, perhaps alerting the animal to movements above.

Like many 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 from a metabolic point of view.

Development

Dissected adult (centre) and two immature specimens

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. At their earliest and intermediate phases of development, there is a pair of fins located near the eyes; as the animal develops, this pair gradually disappears as the other pair develops.^[4] As the animals grow and their surface area to volume ratio drops, the fins are resized and repositioned 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 (Seibel et al. 1998). This unique ontogeny caused confusion in the past, with the varying forms identified as several species in distinct families (Young 2002).

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 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).

Behavior

When encountering a predator or prey, the photophores of Vampyroteuthis change accordingly with its posture, in some ways producing a hypnotising effect.

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 relatives living in more hospitable climes, deep-sea cephalopods cannot afford to expend energy in protracted flight. Given their low metabolic rate and the low density of prey at such depths, Vampire Squid must use innovative predator avoidance tactics 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" or "pineapple posture", the Vampire Squid inverts its caped arms back over the body, presenting an ostensibly larger form covered in fearsome-looking though harmless spines (called cirri).^[5] 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, they are likely to be opportunists. Vampire Squid have been found among the stomach contents of large deepwater fish such as giant grenadiers,^[6] and deep diving mammals such as whales and sea lions.

Relationships

Pyritized fossil of Vampyronassa rhodanica from the Lower Callovian of La Voulte-sur-Rhône.

The Vampyromorphida are characterized by such apomorphies as the possession of photophores, a peculiar type of uncalcified endoskeleton called "gladius", 8 webbed arms and the 2 velar filaments. Until fairly recently known only from the modern species and some fossil remains tentatively allocated to this group, a batch of Middle Jurassic (Lower Callovian, c.165-164 mya) specimens found at La Voulte-sur-Rhône demonstrated that clearly vampyromorphid cephalopods were in existence for far longer than has been hitherto believed.

These were described as Vampyronassa rhodanica. The supposed vampyromorphids from the Kimmeridgian-Tithonian (156-146 mya) of Solnhofen, Plesioteuthis prisca, Leptoteuthis gigas, and Trachyteuthis hastiformis, cannot be positively assigned to this group; they are large species (from 35 cm in P. prisca to > 1 meter in L. gigas) and show features not found in vampyromorphids, being somewhat similar to the true squids, Teuthida.^[7]

Notes

1. ^ Seibel, Brad. "Vampyroteuthis infernalis, Deep-sea Vampire squid". The Cephalopod Page. Dr. James B. Wood. http://www.thecephalopodpage.org/vampy.php. Retrieved 3 July 2011. 
2. ^ Seibel et al. 1999
3. ^ Stephens, P. R.; Young, J. Z. (2009). "The statocyst of Vampyroteuthis infernalis (Mollusca: Cephalopoda)". Journal of Zoology 180 (4): 565–588. doi:10.1111/j.1469-7998.1976.tb04704.x.  edit
4. ^ Pickford 1949
5. ^ "Vampire Squid Turns "Inside Out"". National Geographic. February 2010. http://news.nationalgeographic.com/news/2010/01/100203-squid-vampire-threatened-video/. Retrieved June 2011. 
6. ^ Drazen, Jeffrey C; Buckley, Troy W; Hoff, Gerald R (2001). "The feeding habits of slope dwelling macrourid fishes in the eastern North Pacific". Deep Sea Research Part I: Oceanographic Research Papers 48 (3): 909–935. doi:10.1016/S0967-0637(00)00058-3. 
7. ^ Fischer & Riou 2002

References

• Bolstad, Kat (2003). "Deep-Sea Cephalopods: An Introduction and Overview". http://www.tonmo.com/science/public/deepseacephs.php.  (Version of 5/6/03, retrieved 2006-DEC-06.)
• Ellis, Richard (1996). "Introducing Vampyroteuthis infernalis, the vampire squid from Hell". In Knopf, Alfred A.. The Deep Atlantic: Life, Death, and Exploration in the Abyss. New York. ISBN 0679433244. http://www.thecephalopodpage.org/vsfh.php. Retrieved 2007-APR-30. 
• Fischer, Jean-Claude; Riou, Bernard (2002). "Vampyronassa rhodanica nov. gen. nov sp., vampyromorphe (Cephalopoda, Coleoidea) du Callovien inférieur de la Voulte-sur-Rhône (Ardèche, France)". Annales de Paléontologie 88 (1): 1−17. doi:10.1016/S0753-3969(02)01037-6.  (French with English abstract)
• Pickford, Grace E. (1949). "Vampyroteuthis infernalis Chun an archaic dibranchiate cephalopod. II.". External anatomy (Dana Report) (32): 1–132. 
• Robison, Bruce H.; Reisenbichler, Kim R.; Hunt, James C.; Haddock, Steven H. D. (2003). "Light Production by the Arm Tips of the Deep-Sea Cephalopod Vampyroteuthis infernalis". Biological Bulletin 205 (2): 102–109. http://www.biolbull.org/cgi/reprint/205/2/102.pdf. 
• Seibel, Brad A. (2001). "Vampyroteuthis infernalis". http://www.nhm.ac.uk/hosted_sites/tcp/vampy.html. Retrieved 2006-DEC-06. ^{[dead link]}
• Seibel, Brad A.; Thuesen, Erik V.; Childress, James J. (1998). "Flight of the vampire: ontogenetic gait-transition in Vampyroteuthis infernalis (Cephalopoda: Vampyromorpha)". Journal of Experimental Biology 201 (16): 2413–2424. http://jeb.biologists.org/cgi/reprint/201/16/2413.pdf. 
• Seibel, Brad A.; Chausson, Fabienne; Lallier, Francois H.; Zal, Franck; Childress, James J. (1999). "Vampire blood: respiratory physiology of the vampire squid (Cephalopoda: Vampyromorpha) in relation to the oxygen minimum layer". Experimental Biology Online 4 (1): 1–10. doi:10.1007/s00898-999-0001-2.  (HTML abstract)
• Young, Richard E. (June 2002). "Taxa Associated with the Family Vampyroteuthidae". http://tolweb.org/accessory/Vampyroteuthidae_Taxa?acc_id=2420. Retrieved 2006-12-06. 

External links

• CephBase: Vampire squid
• Tree of Life: Vampyroteuthis infernalis.
• National Geographic video of a Vampire Squid

Images

• The vampire squid's photophores and photoreceptors
• Diagram and images of a Vampyroteuthis hatchling
• Photomicrograph of arm tip fluorescence