The vampire squid is a diminutive deep-sea cephalopod found in the tropical and temperate oceans of the world. The vampire squid grows to about 15 cm (6 inches) in length, and its arms another 15 cm (6 inches) long, bringing the full length of its body to one foot. It thrives in the aphotic zone, which lies 600-900 m (1968-2953 ft.) in the deep ocean. To protect itself from predators, the vampire squid has developed bioluminescence. The vampire squid is the only surviving member of its species, which was originally classified in the order of the octopuses; however, due to its unique physical characteristics, it was assigned a new classification in the order of Vampyromorphida.
The vampire squid can reach a maximum length of 30 cm (1 foot). It possesses a gelatinous body which varies in color from pale reddish to a black velvet hue. Its eyes appear red or blue, and are proportionately large (2.5 cm or 1 inch) compared to other animals. A thin layer of web-like skin connects its eight arms, each lined with rows of fleshy spines. The inside of this coat is black. Mature adults have a pair of small fins protruding on either side of the mantle, which they use to propel themselves throughout the ocean currents. Within the webbing, there are two pouches where the tactile velar filaments are found.
The vampire squid resides in depths ranging from 600-900 m (1968-2953 ft.). Within this region oxygen levels are too low to support aerobic metabolism in higher organisms; however, the vampire squid is able to breathe oxygen saturation of as low as 3%. To survive in this harsh depth environment, the vampire squid has developed a number of physical adaptations, including a low metabolic rate, efficient transport of oxygen through its blue blood, balancing organs which allow them to displace with agility and easiness through the water and a gelatinous body tissue which closely matches the density of the encircling water.
Animals that ascend and descend in the ocean water column possess light-producing organs in their underside. They increase the light level as they ascend, silhouetting their presence against the sky and reduce it as they descend. A fish using this technique (counter-illumination) blends its presence in with the lighter waters above when viewed by a predator below. This is similar to countershading in which deep ocean animals possess light color undersides and obscure backs. Bristlemouths and shining tubeshoulders have ventral light organs.
How the vampire squid uses bioluminescence
The vampire squid generates its own bluish light (bioluminescence). The vampire squid’s body is covered with some type of light-producing organs known as photophores. When threatened, instead of ejecting ink like other cephalopods, the vampire squid expels a sticky cloud of bioluminescence mucus containing a number of orbs of bluish light. Bioluminescence distributes the creature’s silhouette, concealing its presence from the predators below. The luminous stream may last for approximately 10 minutes, and is meant to stun or divert its predators, allowing the vampire squid to move away into the darkness of the ocean.
Bioluminescence is produced by the oxidation of a light-emitting molecule called the luciferin, along with a catalyzing enzyme known as luciferase or photoprotein. Bioluminescence has been found in a great variety of groups of organisms from bacteria and protists to squid and fishes. Bioluminescence is created by the organisms themselves and not by symbiotic bacteria. According to annualreviews.org, bioluminescence comprises all oceanic magnitudes and has evolved a number of times from bacteria to fish to vigorously influence behavioral and physiological adaptations. New technology and methods have allowed scientists to gain a better understanding of the molecular origin of bioluminescence, and its significance in the marine ecosystem.