Vampire squid a human's inner ear) and ammonium-rich gelatinous tissues closely matching the density of the surrounding seawater. Like many deep-sea cephalopods, the vampire squid lacks ink sacs. If disturbed, it will curl its arms up outwards and wrap them around its body, turning itself inside-out in a way, exposing spiny projections. If highly agitated, it may eject a sticky cloud of bioluminescent mucus containing innumerable orbs of blue light from the arm tips. This luminous barrage, which may last nearly 10 minutes, would presumably serve to daze would-be predators and allow the vampire squid to disappear into the blackness without the
Firefly squid having distinct spectral sensitivities. The firefly squid measures about long at maturity and dies after one year of life. It has the standard eight arms and two tentacles, with one pair each having three, bright light-emitting organs at the tips. The squid spends the day at depths of several hundred metres, returning to the surface when night falls. It uses its abilities to sense and to produce light for counter-illumination camouflage: it matches the brightness and colour of its underside to the light coming from the surface, making it difficult for predators to detect it from below. The firefly squid