Vampyroteuthis infernalis has eight long arms and two retractile filaments that can extend well past the total length of the animal and can be retracted into pockets within the web. These filaments function as sensors because of the cirri that cover the entire length of the arm with suckers only on the distal half. There are also two fins on the dorsal surface of the mantle. The vampire squid is so named because of its jet-black skin, webbing between the arms, and red eyes - supposedly characteristics of a vampire. The squid is considered small - reaching a maximum length of 28 cm with the approximate size of a football. There is sexual dimorphism in size: females are larger than males.
The vampire squid has the consistency of a jellyfish, but its most intriguing physical characteristic is that it has proportionally the largest eyes of any animal in the world. A squid six inches long will have eyes that are an in inch across which are comparable to the eye size of a full grown dog.
The vampire squid has black chromatophores with reddish-brown ones interspersed. In contrast to other cephalopods, these chromatophores are non-functional because they have lost the muscles that enable rapid color change. The vampire shares most other features with other octopods and decapods, but it has several adaptations that allow it to live in a deep-sea environment. The loss of most of the active chromatophores and the ink sac are just two examples. The vampire squid also has photophores which are large circular organs which are located posterior to each adult fin and are also distributed over the surface of the mantle, funnel, head, and aboral surface. These photoreceptors produce luminescent clouds of glowing particles that allow the vampire squid to glow.
(Grzimek 1972, Wood and Ellis 1999, Wood 1999)