Inking in a Blue-Ringed Octopus, Hapalochlaena lunulata, with a Vestigial Ink Sac

Here we report for the first time that adult Hapalochlaena lunulata (Quoy & Gairnard, 1832), which has a vestigial ink sac, is capable of inking. Ink was released under three different agonistic conditions: female-female aggression, rejection of mating attempt, and when attacked by a predator. We observed no apparent reaction to the ink by the other animals involved in these interactions