Stomatopod Log Entry: Peacocks attack Blue Ring Octopuses (October 1, 2004)

Contributors: ASJ

Blue Ring Octopuses are one of the most venomous critters on earth, and they are known to prey on smaller stomatopods. However, stomatopods also take their toll on these cephalopods, pulverizing the blue rings with massive blows to disperse the poison before dining on their prey.

In the excerpt below, the beautiful Peacock mantis shrimp Odontodactylus scyllarus, a pair of which once killed 6 trigger fishes in a row, shows why not even one of the most poisonous creatures on earth can withstand its deadly attacks!

From: Inking in a Blue-Ringed Octopus, Hapalochlaena lunulata, with a Vestigial Ink Sac by Christine L. Huffard and R. L. Caldwell

During laboratory studies on Hapalochlaena lunulata obtained from Indonesia, we recorded seven instances when adults released a single, poorly defined cloud of brown ink. In each case, the small puff of ink diffused in seconds. The octopuses ejecting the ink did not jet from the inked area. We observed no apparent direct reaction to the ink by the other animals involved in these situations.

Two adult octopuses (one male and one female) inked as they attempted to escape from an attack by a stomatopod, Odontodactylus scyllarus (Linnaeus, 1758). Another male inked as it jetted away from a nearby stomatopod.

The inkings we observed by H. lunulata are not easily attributable to any of the usual explanations of inking behavior mentioned previously. Because the thin, transient cloud of ink released neither impairs visibility nor retains any shape in the water column, it does not serve as a smoke screen or a pseudo-morph. Cephalopod ink may irritate the chemosensory systems of some animals (Gilly and Lucero 1992), but it appears to offer no protection from O. scyllarus. Attacking stomatopods continued to pursue, and eventually killed, the two octopuses that had inked.

Because the highly visual O. scyllarus may be an effective predator even with dulled olfactory receptors, the ability of H. lunulata ink to inhibit the approach of predators that rely more on chemosensory information should be investigated. In five of the seven situations, ink was released after provocation by a conspecific. No animal jetted immediately from the area, as would occur in response to an alarm.


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