The many octopus species that live beyond the reach of vacationing snorkelers, scuba diving researchers and even near-shore commercial fisheries are relative unknowns compared with the more familiar shallow-water species. But that doesn't mean that they are not of great importance to science—and the ocean's intricate food web.
Last time we met the super-fecund cephalopod the football octopus (Ocythoe tuberculata). Today, we try to catch a glimpse cirrate octopus Opisthoteuthis calypso, which seems to fly along the deep ocean floor under the power of its winglike fins.
Once assumed to be one in the same as close relative O. agassizii, O. calypso was at last recognized as a separate species in 2002. It has still proven so rare, however, that it has yet to be granted a common name. The authors of a recent review paper, published online in February in Mediterranean Marine Science, found just 12 reports of the species over 16 years (1994-2010)—and all were from dedicated scientific samplings.
Since its distinction as a species, records have placed the curious O. calypso in the eastern Atlantic and Mediterranean at a wide range of depths—between 365 and 2,208 meters below the surface.
These certainly aren't the speediest octopuses in the sea. Most video footage of their Opisthoteuthis relatives looks like they are moving in slow motion—at least to our eyes.
O. calypso seem to feed mostly on small, easy-to-grab animals, such as small crustaceans and marine worms that live on and just above the mucky surface. Adults might have fewer than 60 suckers on each webby arm (compared with giant Pacific octopuses' 280 strong grippers per arm). But this cirrate octopus also has small hairlike "cirri" on each appendage. The cirri themselves are not longer five millimeters each but might play an important role—like squid's hooks—in bringing in dinner.
These cirrate octopuses (in the suborder cirrina), with their earlike fins and relatively simple arms, might be the relics of the octopus family. Early octopod fossils from more than 290 million years ago suggest the presence of similar fins and suckerless arms.
The O. calypso is a close relative of the better-known flapjack octopus O. californiana (which, in turn, is perhaps even more familiar as a model for the character Pearl in Disney's Finding Nemo). As a genus, these Opisthoteuthis octopuses are super-flat and generally red or orange in color, earning them the nickname flapjack devilfishes. The family in which they reside, the Opisthoteuthidae, are also sometimes called umbrella octopuses, for their wide webs that extend much of the way down their arms.
Unlike many other octopuses, the O. calypso males seem to outgrow the females—the biggest fellows reaching 48 centimeters from head to arm tip and 5.4 kilograms (the females were a slight 34 centimeters long and 1.7 kilograms).
Next, we will check in on the strange and wonderful blanket octopus (Tremoctopus), which has some extra large ladies and super tiny males; think a human-sized gal and something like a walnut-sized guy.
In the meantime, enjoy some rare footage of the O. calypso's close cousin O. agassizii:
Illustration courtesy of Ivan Phillipsen