Thursday, July 18, 2013

Musing on the The Marvelous Octopus

I don't know what brought octopuses (that is the proper plural) to mind today.  But they are are an amazing group. 
They have, essentially, part of their brains distributed throughout their skins.  They are the masters of camouflage.  They can be huge.  They are great escape artists, as anyone who'd kept them in tanks can attest. And they are smart.  We don't know exactly how best to test them, but what we can tell is that they are a lot smarter than you'd expect of what looks to us like a blob with eyes.  They are tool-users, even tool-makers.
They can be impossibly weird.  Take the gelatinous octopi of the genus Allapossus, short-armed, large-eyed creatures with a maximum span of at least two meters.  Gelatinous octopi are so called because their flesh is soft and translucent, as if they were jellyfish pressed into an octopus mold.  One found in the 1980s sported  eyes six inches across. Or take the new deepwater species spotted by the submersible Alvin in 1994.  The world's press carried the tale of this seemingly confused mollusc, a male about 15" long.  It was attempting to mate with a much larger octopus – also a male.  Apparently encounters are so rare in the depths that octopuses will try a match with any of their kind they come across: not what we humans would call “safe sex,” since you’re as likely to be eaten as you are to procreate.  The crew of the French submersible Cyana a spotted another new species of cirrate, or fringed, octopus in 1989.  This cephalopod, also a Pacific denizen, displayed truly bizarre behavior.  When poked by the sub’s robot arm, the annoyed octopus gathered its arms together, trapping water in the membranes between them and taking on the appearance of a submarine pumpkin.  This action is presumably designed to startle predators.  It certainly had that effect on the French aquanauts. 

But back to the camoflauge thing. The champ is the recently  described mimic octopus (Thaumoctopus mimicus), which changes it colors, shape, and texture to imitate fish, crabs, sea snakes, and my other creatures, mimicry may be more widespread than we’d thought. The Atlantic longarm octopus (Macrotritopus defilippi) can mimic a species called the peacock flounder by swimming with its arms trailing back like fins and tail. It even contorts its body to bring the eyes close together on one side. When a diver reported seeing this off the Netherlands Antilles and passed this information to Roger Hanlon of the Marine Biological Laboratory at Woods Hole in 2004, Hanlon flat-out didn’t believe him – until the diver showed him a picture. Mimicry by any Atlantic cephalopod was unknown.  As Hanlon points out, a lot of animals camouflage or imitate, but the illusion only holds while they remain still. Cephalopods – a few of them, at least – take it much further by mimicking movement and keeping the appearance of something else while on the move.  (A special case is a species of cuttlefish in which males look like females to clip past other males and get close to desired females.)  Some deep-water species of octopus (and squid) are normally transparent but can switch instantly to being “colored in” with red pigment if that will help avoid a predator.

Yep, octopuses are weird. There's a scientific term for you.  But nothing else fits. 
(Photos NOAA)

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