http://www.smithsonianmag.si.edu/smithsonian/issues96/may96/vampire_jpg.html As an example of the mysterious nature of the deep-water cephalopods, consider Vampyroteuthis infernalis, whose name can be translated as "vampire squid from Hell." About a foot long, this deepwater denizen is among the most fascinating animals on earth. It was first described in 1903 by Carl Chun, a German teuthologist who identified it as an octopus, because it had -- he thought -- eight arms. Then another pair of thin arms was discovered, tucked into pockets outside the web that connects the eight arms. Taxonomically speaking, it hovers between octopus and squid in its own order, the Vampyromorpha. The squid has large fins at the to of its body that resemble large ears. It is very gelatinous in form, resembling a jellyfish more than the common squid. The vampire squid has the largest eyes of any animal. It is a small animal, growing to a length of about six inches, bit it has globular eyeballs as large as the eyes of a large dog. The vampire squid's body is covered with light-producing organs called photophores. This gives the squid the unique ability to "turn itself on or off" at will. When the photophores are off, the squid is completely invisible in the dark waters where it lives. These squid live as deep as 3000 feet. Unlike other squid and octopi, the vampire squid has no ink sack. The vampire squid's arms are covered with sharp tooth-like spikes. This gives the animal its name. One pair of arms has been modified into retractile filaments that can extend to twice the body length of the animal. The squid may use these arms to capture its prey. When threatened, the squid can draw its arms up over itself and form a defensive web that covers its body. The vampire squid can swim extremely fast for a gelatinous animal. It can reach a speed of 2 body lengths per second and can accelerate to this speed in only 5 seconds. If danger is present, it can make several quick turns in an attempt to escape its enemies. Vampyroteuthis infernalis is named for its jet-black skin (although their color varies from black to red to purple and seems to depend on the light conditions), the caped appearance of the webbing between the arms, and eyes that appear red under some light conditions (the eyes appear blue when viewed from a submersible). William Beebe (1926) described V. infernalis as "a very small but terrible octopus, black as night with ivory white jaws and blood red eyes". Despite this horrific description, V. infernalis is a rather docile animal, and most often hangs motionless in the water column, with only slight movements of the fins for balance. Dr. Richard Young (1964) wrote that V. infernalis "has no more control over its location in the water column than that exercised by the common jellyfish". V. infernalis does, in fact, have the lowest metabolic rate of any cephalopod ever measured (Seibel et al., 1997).