When feeling threatened Aplysia dactylomela will elicit a quick downward movement of its parapodia over its back. It may also release foul fluids from both the opaline gland and the purple dye cavity.
The idea that Aplysia dactylomela releases ink and opaline in defensive situations is widely held. Much of this ascription is based on electroneurophysiological studies. However, further studies were unable to confirm that inking was due to interaction with a predator. (Barnes, 1963; Tobach, Zaferes, and Migenis-Lopez, 1989; Wilbur and Yonge, 1966)