Vampire Squid: A bloodthirsty terror of the deep sea?
When people hear the word vampire, they immediately associate it with something terrifying that lurks in the darkness, waiting to attack. While the vampire squid does live in darkness, it isn’t as terrifying as its name may lead people to believe. The Latin name for the Vampire Squid is Vampyroteuthis infernalis, this translates into “vampire squid from hell” and are the only known living members of the Order Vampyromorphida. However, the vampire squid is not actually a true squid. It is a unique member of the Class Cephalopda and has many similarities to both octopuses and squids. It is said to be a living fossil as it has had very little evolutionary changes through time. We will explore the morphology and life of the vampire squid to determine whether it truly deserves the title of being a bloodthirsty animal of the deep sea.
The vampire squid has two large fins on the top of its body (dorsal surface) that resemble ears, these are used for propulsion, allowing it to glide through the water. They undergo a form of metamorphosis, which allows the size, shape, and position of their fins to grow and develop. When the mantle reaches 15-25 mm a second pair of fins start to grow in front of the first pair of fins. When the second pair of fins have reached maturity the first pair is reabsorbed, this also changes the way that the vampire squid swims. The vampire squid originally uses jet propulsion to swim but after its metamorphosis it switches its swimming style to fin propulsion. Depending on how much light is available, their eyes appear red or blue and tend to be relatively large in comparison to their body size, which can reach a maximum length of 28 cm, which is about the same size as and A4 piece of paper. The colour and size of their eyes are identifying features as well as their reddish-brown skin and the webbing around its arms.
How have they adapted to live in the deep sea?
The vampire squid has black chromatophores that are mixed in with reddish-brown ones, but they do not work the same as they do in true squids. This is because the vampire squid does not have the correct muscles that control colour change. The body of the vampire squid is covered with photophores, these are light producing organs. This makes them well adapted to live in deep sea environments. Photophores can be found on the posterior end of each fin and are distributed across the mantle, head and the aboral surface (surface opposite the mouth). Photophores allow for bioluminescence and to a vampire squid, they act like a light switch as they have the ability to switch the photophores “on” and “off”. When the photophores are switched “off” the vampire squid is in complete darkness and is invisible to predators. They have complete control over the photophores, they have the ability to regulate the size and intensity. This allows them to create complex patterns, which can be used to attract prey or disorient predators. The photophores are used as their main form of defence as they lack the ink sacs that are present in true
squid species. Another defence mechanism that is used when they feel threatened is that the vampire squid will move its fins toward the funnel and emit a jet of water off the mantle. A typical defensive posture has been described as a “pineapple posture”, this is when the arms and web are spread over the mantle and head, essentially turning itself inside out, and the picture on the right displays this transformation. This position protects the head and mantle, and also camouflages the squid. When in this position a series of spines, that may look threatening, are displayed. These spines may look intimidating to predators, and maybe even humans, but the spines are actually harmless.
Similar to octopuses, they have eight arms but unlike octopuses they have two filaments that stretch out past their body length that they use for feeding, as shown in the image. These filaments can retract into pockets that are found in the webbing between the arms. There is little known on what vampire squids feed on but they do have one of the lowest mass specific metabolic rates of any cephalopod. However, we do know that they are a carnivorous species and it has been reported that they tend to feed on copepods, prawns and cnidarians. They also rely heavily on marine snow, they use their filaments to capture the falling particles. Marine snow is rich in nutrients and is made up of mainly detritus and faeces. The beaks of vampire squids have been found in the stomachs of large deep diving fishes, seals and whales.
Where can they be found?
Vampire squids can be found in both temperate and tropical regions of the ocean. They live within the mesopelagic zone, down to the bathypelagic zone. This is at depths of 300-3000 meters, where little to no light penetrates. Most vampire squids are found at depths of 1500- 2500 meters, this is known as the oxygen minimum zone (OMZ). The OMZ is an area where oxygen saturation is very low. There is a low circulation of water, and most species are unable to live in these areas. Therefore, making the abundance and diversity of species in the oxygen minimum zones low.
So, are they really bloodthirsty terrors of the deep sea?
They may have been given a name that people associate with something negative but the vampire squid is basically a harmless creature. Growing to about as big as a piece of A4 paper and having no real defensive mechanisms the vampire squid isn’t harming anyone, especially living in an area that is very remote and empty. The vampire squid has managed to adapt to its environment and remain relatively unchanged, making it a living fossil. So, despite many misconceptions related to its name, the vampire squid really isn’t a bloodthirsty terror of the deep sea and it has even been used as a character on the children’s t.v show, Octonauts!