The Vampire Squid (Vampyroteuthis infernalis) is a mysterious and little known squid. It lives deep in the ocean, sometimes as low as 3000 feet down! The Vampire Squid is not the vicious predator you might expect. Though it is true that the Vampire Squid is a carnivore, being about 6 inches long does not make it much of a threat. However, it doesn't mean that this mollusk is plain and boring. On the contrary, the Vampire Squid is a wonder to behold. With it's intriguing photophores that light the darkness of the Abyss and unusually intimidating defenses, this creature of the deep is anything but ordinary.
The Vampire Squid has a gelatinous form that slightly resembles a jellyfish.  The female is usually larger in size than the male.  The skin of the Vampire Squid is usually reddish or black, but can vary in color. They generally have very large blue or red eyes, but colors can vary.  In fact, this invertebrate has the largest eyes-to-body-size ratio of any animal. The Vampire Squid only grows approximately six inches in length, but its eyes are similar in size to that of a large dog's.  The squid has eight long arms and two stretchy arms that can retract into pockets, which are located on the webbing between the arms. These special "arms" have only been found in this particular species of squid. The eight arms have suckers on the distal parts of the arm, farthest away from the mantle. (The mantle is a thick covering of skin that is used to protect the major organs) The squid also has two fins on the back part of the mantle, that are used to create momentum. Unlike most squids and octopi, the Vampire Squid does not have an ink sac. It doesn't need one at the pitch-dark depth of 3000 feet.
One of the most interesting parts of this organism is its metamorphosis. It's fins change in size, shape and position as it grows. When the mantle is 15-22 mm in length a second pair of fins grow in front of the first pair. When this new pair is fully developed, the original pair is absorbed back into the mantle. These new fins make the Vampire Squid rely more on fin propulsion instead of the jet propulsion that it used as a young squid. The squid also has photophores. They are large and circular and are found on the hind end of each fin. The photophores are also spread around the mantle, funnel, head, and aboral surface. These photophores produce glowing particles that will gleam for anywhere from two to nine minutes. The Vampire Squid can jettison glowing particles when it anticipates danger. This function confuses its predators and gives the squid a chance to slip away into the darkness. (Grzimek 1972, Wood and Ellis 1999, Wood 1999). The Vampire Squid has highly advanced statocysts, which help the squid maintain balance. These statocysts give them nimbleness, which is much needed in the dangerous abyss. This organ incorporates a sac-like structure and many sensory hairs.  These statocysts are ammonium rich, which makes them as dense as the surrounding water. This helps the Vampire Squid not to sink to the bottom of the ocean and it also ensures that it does not float to higher water. 
The female Vampire Squid receives packets of sperm from the male called spermatophores. The reproductive organs of the male are found inside the male's funnel.( The funnel is located in the mantle and is used for jet propulsion, waste excretion, and reproduction.) The packets go into receptive ducts below the female's eyes. The packets are stored there until she wants to use them to fertilize her eggs. It is believed that the female creates an egg mass inside of her oviducts. It is assumed that the eggs can be held inside the female's oviducts for up to a year. (All Vampyromorph octopods can maintain both oviducts unlike cirrate octopods.) Once the female decides the eggs are to be fertilized, she will remove the sperm packet from the receptor and place it into the oviduct with the eggs. The fertilized eggs will grow to about 3-4 mm in diameter inside the female. Once they are developed enough, they are released into the water in small groups. When the eggs hatch they are 8mm and are transparent. The young look dramatically different than the adults. Their heads are not yet fused to the mantle and they do not have the webbing in between their arms. They do not have fully developed fins, so they only use jet propulsion when needed and drift along in the water. These hatchlings tend to drift to deeper waters than the adults do. In these deeper waters, the new squids mature slowly. Too young to hunt, they survive by devouring their left over yoke. Slow development is believed to be due to lack of food in the deep waters. As with most cephalopods, the female most likely dies shortly after releasing her fertilized eggs. 
The Vampire Squid is a carnivore, which means it eats the flesh of other organisms. The Vampire Squid has been known to eat copepods, prawns, and cnidarians. In order to find food, the Vampire Squid uses sensory filaments to feel around for its prey.  It uses light-producing organs called photopores at the tip of each arm, to give the appearance of numerous small prey. The Vampire Squid will then swim around in a circle until it catches something.  With one pair of arms able to extend twice the length of it's body, the Vampire Squid can quickly catch prey. The squid can swim very fast, even with a gelatinous body. At top speed, it can travel up to two body lengths per second. The Vampire Squid also has its share of predators. Vampire Squid beaks have been found inside the stomachs of large deep swimming fish, pinnipeds, and whales. Even with its sharp spike-like hooks on each arm, it is no match for these predators of the deep.  When the Vampire Squid is threatened by a predator it will "turn on" it's photophores and then make them shrink in size. This will give the predator the illusion that it's meal has left. If the Vampire Squid touches an animal, it can squirt glowing particles made of bacteria into the water to confuse the predator. It can also "turn on" its photophores and flail its arms. This can disorient the predator by allowing the Vampire Squid to appear as several very small fish or prey that is much further away. 
Respiration without much oxygen
The Vampire squid has an amazing respiration system. They have an oligoaerobic system. ('oligo' meaning a few and 'aerobic' meaning oxygen) This squid definitely needs one! The Vampire Squid lives in an almost oxygen free layer of the ocean. These layers can have less than 5% air saturation. Most cephalopods cannot survive unless there is at least 50% saturation. (Seibel et al., 1999; Wells and Wells, 1995)  The Vampire Squid has a heightened ability to draw oxygen from the water. It has a very low metabolic rate and much of its gills are on the surface of its body. (Madan and Wells, 1995; Seibel and Childress, 1996) The Vampire Squid's hemocyanin  (a bluish, oxygen carrying substance that contains copper, similar to hemoglobin)  helps it hold onto and transport oxygen much more efficiently.  This allows it to function with out having an aerobic metabolism. Compared to its mass, the Vampire Squid's metabolism is the lowest of all animal life. (Madan and Wells, 1995; Seibel and Childress, 1996)  It seems this invertebrate breaks a lot of records! 
- Vampyroteuthis infernalis video National Geographic .
- Vampyroteuthis "vampire squid from hell" - Planet Earth Planet Earth (excellent footage of photophores!)
- Vampire SquidThe Sea, Monsters of the Deep .
- Vampyroteuthis infernalis Vampire Squid Marine Bio
- Vampyroteuthis infernalisTONMO article by: Phil Eyden
- Vampyroteuthis infernalisJohnson, B. 2000, Animal Diversity Web.
- Vampyroteuthis infernalis, Deep-sea Vampire squidThe Cephalopod Page, article and photograph by Brad Seibel
- Vampire SquidWikipedia, many authors
- hemocyanin definitionEncyclopedia of Science
- Vampire SquidAbsolute Astronomy, Explore the Universe of Knowledge
- How Stuff WorksHow Squid Work by Stephanie Watson