Physical Description
The vampire squid reaches a maximum total length of around 30 cm (1 ft). Its 15-cm (6-in) 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 in) in diameter. The animal's dark color, cloak-like webbing, and red eyes are what gave the vampire squid its name.
Mature adults have a pair of small 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 octopi.
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 undersides 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 ability would not be useful at the lightless depths where it lives.
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