Almost all cephalopods- the tentacled class of marine mollusks that include the octopus, squid, and cuttlefish- have the ability to eject dark ink from their body as a method of escaping predators. The melanin-based ink is stored in an ink sac until it is released to create a dark cloud in the water, giving the cephalopod time to flee from danger.
Cephalopod ink is mainly used in cooking to create dark-colored foods or as medium for painting. This sample however has not been preserved for consumption. Please do not eat.