This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Down in the dark depths of the deep ocean live more than a dozen species of "Dumbo" octopuses.
These octopods from the genus Grimpoteuthis are so named for their prominent, unusual earlike fins that they use to help them swim (reminiscent of the Disney elephant character who used his ears to fly). These graceful, gelatinous octopuses are not only bizarre looking, but they are also marvels of evolutionary engineering. Living mostly some 3,000 to 4,500 meters (9,800 to 14,800 feet) down, they can stand pressures of more than 5,000 pounds per square inch.
In this high-pressure world most swim just above the sea floor, hunting for local crustaceans, worms and bivalves, which they are thought to swallow whole (unlike many other octopuses, which have sharp radulas to help dismantle prey before sucking meat out of the shells).
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As members of the "umbrella octopus" family (Opisthoteuthidae), these cephalopods have extensive webs, which often extend nearly to the tip of their arms. And belonging to the cirrate octopus group, they possess few suckers, but many of those suckers are equipped with a couple small cirri, small protuberances, which might help them catch prey.
Unlike most octopuses, the "Dumbo" octopuses have primitive internal shells, which grow in a "U" shape. These structures are thought to help support the substantial fins. They also have large eyes for a deep-sea octopus, often measuring a third of their entire head width.
Whereas most individuals described are just dozens of centimeters long, one caught on a research expedition in 2009 measured in at 1.8 meters (about six feet) long and about 6 kilos (13 pounds). Many preserved specimens are a poor representation of what these animals look like in life, deep in the ocean. Kept in a standard ethanol fix, their bodies and webs often shrink a great deal, leaving their fins and limbs to appear much enlarged.
These bizarro octopuses have been found at extreme depths all over the globe, including the Philippines, New Guinea, New Zealand, Australia, the Pacific Northwest and even off the coast of Martha's Vineyard.
Owing to their extreme habitats and the vast deep oceans, we don't know much about these octopuses and their life cycles. Some reports of dissected females note eggs of various sizes, suggesting she could lay broods at various times in her life. Each egg is relatively large and has a casing that hardens when it comes into contact with the water.
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Illustration courtesy of Ivan Phillipsen