The octopus's boneless body is well-suited to changing shape. It can flatten out or contract inward in a variety of shapes. But out of the more than 700 cephalopods that cruise the global seas, the mimic octopus's imitation skills mystify scientists the most: It's the first invertebrate species known that can systematically copy multiple species' appearances.
The mimic octopus is new on the scene, discovered barely a decade ago in 1998. And the species was only recently named -- Thaumoctopus mimicus. The mimic octopus lives off the coast of Indonesia and Malaysia in shallow, open waters. That habitat differs from the more common octopus dwellings near coastal reefs or rocky ocean floors that provide an abundance of hiding places [source: Turner]. Because of its relatively unprotected surroundings and its daytime foraging habits, the mimic octopus would be a sitting duck for local predators were it not for its many disguises.
Rather than just blending into the surrounding environment like many other octopuses, the mimic octopus takes on the form of venomous creatures. In particular, its lionfish and sea snake imitations are spot-on. A sea snake looks like any other snake you'd see on land with black and white banding. How does an eight-armed octopus do a believable snake impression? Coloration isn't a problem thanks to those pigment-filled chromatophores we discussed earlier. Then, it simply tucks six of its legs into a hole and extends the remaining two. A lionfish, with its fan of poisonous spines, seems a little harder to pull off, but it's a cinch for the mimic octopus. The cephalopod compresses its head into the shape of the lionfish body and fans its tentacles around it like spines.
Proving the validity of the mimic octopus's imitations required hours of video and photographic documentation [source: Norman]. Drawing conclusions about the intent behind the mimicry can be like two people cloud-gazing: One may see a bulldozer while the other makes out a dragon. However, the evidence gathered indicates a definitive method behind the mimic octopus's miming. For instance, researchers observing its actions found that the octopus only pulled out the sea snake impression in the presence of predatory damsel fish [source: Norman]. Why is that significant? Sea snakes feed on damsel fish. Also, those two species are only a small sampling of mimic octopuses' masks. Experts also think they've witnessed up to 13 different species imitations, including jellyfish, anemone and mantis shrimp, but they have yet to confirm them all [source: Hanlon, Conroy and Forsythe].
Even more intriguing than the mimicry action is the implied intelligence behind the behavior. It's well-established that octopuses have large brains in relation to their body size and are capable of learning. The mimicry is likely innate for the mimic octopus, but nevertheless requires the brainpower to recognize predatory species and know the appropriate form to take on [source: Norman et al]. How exactly they picked up their broad repertoire of impersonations is still unknown.
Perhaps we've been seeing mimic octopuses for a long time but mistaking them for something else. Whatever the case, these masquerading masterminds of the deep have certainly made waves in the scientific community in their 10-year history.
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More Great Links
- Butvill, David Brian. "The Changeling." Current Science. Oct. 7, 2005.
- Hanlon, Roger T.; Conroy, Lou-Anne; and Forsythe, John W. "Mimicry and foraging behaviour of two tropical sand-flat octopus species off North Sulawesi, Indonesia." Biological Journal of the Linnean Society. Vol. 93. Issue 1. Dec. 17, 2007. (Oct. 31, 2008)http://www3.interscience.wiley.com/journal/119394156/abstract?CRETRY=1&SRETRY=0
- Hamilton, Garry. "Houdini With Eight Arms." Equinox. June/July 1997.
- Milius, Susan. "It's a snake! No, a fish. An octopus?" Science News. Sept. 1, 2001. (Oct. 31, 2008)http://www.sciencenews.org/view/generic/id/1951/title/Its_a_snake!_No,_a_fish._An_octopus%3F
- Norman, Mark D.; Finn, Julian; and Tregenza, Tom. "Dynamic mimicry in an Indo-Malayan octopus." Proceedings of the Royal Society. Vol. 268. No. 1478. Sept. 7, 2001. (Oct. 31, 2008)http://journals.royalsociety.org/content/pp95mdq58uyhe4ru/
- Norman, Mark. "Masters of Mimicry." Nature Australia. Spring 2002.
- "On the other seven hands." Economist. Sept. 1, 2001.
- Turner, Pamela S. "Meet an eight-legged actor." The Christian Science Monitor. March 5, 2002. (Oct. 31, 2008)http://www.csmonitor.com/2002/0305/p18s02-hfks.html