ink sac

An ink sac is a specialized organ found in many cephalopods like squids and octopuses. It stores a dark ink that these animals can release as a defensive mechanism. When threatened, they squirt ink into the water to create a cloud that obscures the predator's view, allowing the cephalopod to escape. The ink is produced in the ink sac and released through the siphon. This clever adaptation helps them avoid predators in their often dangerous ocean habitats.