Vampire Squid - Habitat and Adaptations

Habitat and Adaptations

The vampire squid is an extreme example of a deep-sea cephalopod, thought to reside at aphotic (lightless) depths from 600–900 metres (2,000–3,000 feet) or more. Within this region of the world's oceans is a discrete habitat known as the oxygen minimum zone (OMZ). Within the OMZ, oxygen saturation is too low to support aerobic metabolism in most higher organisms. Nonetheless, the vampire squid is able to live and breathe normally in the OMZ at oxygen saturations as low as 3%; a feat no other cephalopod, and few other animals, can claim.

To cope with life in the suffocating depths, vampire squid have developed several radical adaptations. Of all deep-sea cephalopods, their mass-specific metabolic rate is the lowest. Their blue blood's hemocyanin binds and transports oxygen more efficiently than in other cephalopods, aided by gills with especially large surface area. The animals have weak musculature, but maintain agility and buoyancy with little effort because of sophisticated statocysts (balancing organs akin to a human's inner ear) and ammonium-rich gelatinous tissues closely matching the density of the surrounding seawater.

At the shallower end of the vampire squid's vertical range, the view from below is like the sky at twilight: The highly sensitive eyes of deepwater denizens are able to distinguish the silhouettes of other animals moving overhead. To combat this, the vampire squid generates its own bluish light (bioluminescence) in a strategy called counterillumination. The light diffuses the animal's silhouette, effectively "cloaking" its presence from the watchful eyes below. Its own large eyes detect even the faintest of gleams. A pair of photoreceptors is located on top of its head, perhaps alerting the animal to movements above.

Like many deep-sea cephalopods, vampire squid lack ink sacs. If threatened, instead of ink, a sticky cloud of bioluminescent mucus containing innumerable orbs of blue light is ejected from the arm tips. This luminous barrage, which may last nearly 10 minutes, is presumably meant to daze would-be predators and allow the vampire squid to disappear into the blackness without the need to swim far. The display is made only if the animal is very agitated; regenerating the mucus is metabolically costly.