MBL, WOODS HOLE, MA—On the open sand plains of the Caribbean seafloor, where soft-bodied animals are routinely exposed to predators, camouflage can be key to survival. Perhaps no group of animals is quite as adept at blending in with its surroundings as cephalopods, who along with relatives the cuttlefish and squid, have evolved a unique skin system that can instantaneously change their appearance.
In the February 2010 issue of The Biological Bulletin, MBL Senior Scientist and cephalopod expert Roger Hanlon and his colleagues report the exceptional camouflage capabilities of the Atlantic longarm octopus, Macrotritopus defilippi, whose strategy for avoiding predators includes expertly disguising itself as a flounder. While Hanlon and others have documented two other species of octopuses imitating flounder in Indonesian waters, this is the first report of flounder mimicry by an Atlantic octopus, and only the fourth convincing case of mimicry for cephalopods.
Comparing still photographs and video footage from five Caribbean locations collected over the last decade, Hanlon and co-authors, MBL graduate students Anya Watson and Alexandra Barbosa, observed uncanny similarities between the small and delicate octopus and the peacock flounder, Bothus lunatus, one of the most common sand dwellers in the Caribbean. They compared not only coloration, which in each animal resembled the sandy seafloor, but swimming speed and form.
Just like flounder, the octopuses contoured their bodies to hug the wavy seafloor, tapering their arms behind them. They also swam with the same fits and starts as flounder at the same speeds. Interestingly, the octopuses mimicked flounder only when swimming, when movement would compromise their camouflage. How well the animals blended in with their background differed. The octopus showed more highly controlled and rapid skin patterning than the flounder, whose camouflage was slower and less precise.
"We were equally impressed with the remarkable camouflage of this small octopus species even when it was stationary yet entirely exposed on top of the open sand," says Hanlon. "The apparent match in pattern, color, brightness, and even 3-dimensional skin texture was noteworthy even when compared to other changeable cephalopods. They also demonstrated an unusual form of disruptive camouflage."
So why do Atlantic longarm octopuses choose to imitate flounder as a way to avoid the threat of predators? More study of cephalopod mimicry is needed, but a possible explanation, according to Hanlon and his team, could be that predators who could easily take a bite out of the small, soft octopus might find a rigid flatfish like the flounder too much of a mouthful and avoid them.
This research was supported by grants from the Sholley Foundation, Office of Naval Research, Our World-Underwater Scholarship Society, and Fundaca˜o para a Cieˆncia e a Tecnologia, Portugal.
For a copy of the paper, please contact Carol Schachinger at cschachi@mbl.edu or visit The Biological Bulletin online at www.biolbull.org.
Published since 1897 by the Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts, The Biological Bulletin is one of America's oldest, peer-reviewed scientific journals. It publishes outstanding experimental research on the full range of biological topics and organisms, from the fields of Neuroscience, Behavior, Physiology, Ecology, Evolution, Development, Reproduction, Cell Biology, Biomechanics, Symbiosis, and Systematics; and it especially invites articles about those novel phenomena and contexts characteristic of intersecting fields. The electronic version, Biological Bulletin Online, contains the full content of each issue, including all figures and tables, beginning with the February 2001 issue. PDF files of the entire archive from 1897-2000 are also available.
The MBL is a leading international, independent, nonprofit institution dedicated to discovery and to improving the human condition through creative research and education in the biological, biomedical and environmental sciences. Founded in 1888 as the Marine Biological Laboratory, the MBL is the oldest private marine laboratory in the Americas. For more information, visit www.MBL.edu.
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Biological Bulletin