Monday, March 30, 2009

Apple #377: Octopi

Recently, I saw a news story about an octopus in aquarium that escaped from her tank. I'm not exactly sure how she did it, but she also managed to open some sort of valve that allowed salt water to gush out onto the floor of the aquarium -- 200 gallons of it. She survived the flood, as did all the other animals in the aquarium. After the staff closed up the place in her tank where she busted out, she "sits in her tank as if nothing happened."

This reminded me of a YouTube video a friend of mine told me about a while back where you can watch an octopus do all sorts of things -- including opening a jar to get a a crab inside, finding its way into an Erlenmeyer flask also to get at its lunch, and squeezing itself through a narrow tube. Watching this video was pretty much how I learned just how wily octopi can be.

Here's the video he told me about. And no, I don't know what's up with the music.

That video is edited so you can't really see how the octopus removes the jar lid. In this one, you can see the entire process from start to finish. I think the noises in the background are the TV and the octopus owner's bird.

  • Scientists don't know that much about octopi because they're very good at avoiding humans, and they tend to hide when divers come around to look at them.
  • Another reason it's hard to study them, says one biologist at UC Berkeley, "If you watch them, they watch you back."
  • Octopuses are cephalopods (squids, octopuses, cuttlefish, and nautiluses). The word cephalopod comes from a Greek phrase which means "head-footed." Their bodies are really a squishy head which is called the mantle, a bunch of arms, and a foot. The foot is the thing they grasp with and it is attached to the head, hence the name.
  • Scientists think that cephalopods have been around for 500 million years.
  • All cephalopods have three hearts. Two of the hearts pump blood to the gills and one pumps blood to the rest of the body.
  • Another feature of cephalopods is that they have eyes that look a lot like human eyes, and they are "vision-forming," which means they aren't just spots designed to look like eyes and fool possible predators, but they actually work and help the cephalopods to identify and track the food they're about to eat.
  • The ink that most cephalopods expel to confuse any attackers is made of melanin, the same stuff that pigments your skin.
  • Cephalopods have large brains and some species are known to be able to learn and retain information. I'm willing to bet that, since we don't know all that much about them yet, scientists will find out that even more species of cephalopods can learn, and that they're all a lot smarter than people realized.
  • All cephalopods are nocturnal.

The Coconut Octopus in Sulawesi. Impressive creature, isn't it?
(Photo by Alistair Watters)

  • As you probably learned in elementary school, octopuses have eight arms.
  • Octopuses mostly eat crustaceans like crabs, shrimp, lobster. They'll also eat clams or fish, and they may also eat other octopuses.
  • The Smithsonian and other zoos are trying to learn more about octopus behavior and capabilities by putting stuff into the tank with their octopus -- things like jars with lids, laundry baskets, shelves, doorways, rubber dog toys, etc. -- and seeing what the octopus does with them. Octopuses will inspect these items, climb on them, or if they're small enough, move them around in the water with jets of air -- effectively playing with them.
  • One researcher put a bunch of stuff like plastic jugs, plates heaped with pebbles, and clumps of algae in the bottom of an octopus tank, making a maze that hid the exit. She tried this out on a few different octopuses, and it only took a few tries before they found not just the exit, but the quickest way to get there.
  • She even moved them from one maze to a second one and back again, and they were apparently able to remember what they'd learned the first time they'd been in the maze.
  • Octopuses are also very skilled at camouflage. They can suddenly change their skin color to match the color of coral or nearby plants, or they can turn themselves completely white to scare off a predator. It's not an octopus, it's a ghost octopus!

The Blue-ringed Octopus is venomous. It turns its rings bright blue to warn predators. If they get too close, this octopus can bite and inject the neurotoxin into the wound through its saliva. The venom is so potent, it can cause heart and respiratory failure in a human being within minutes.
(Photo by Roy Caldwell, California Academy of Sciences)

Here are some photos of the Blue-ringed octopus camouflaging itself.

  • One particularly impressive trick is to make themselves look like a rock. But they don't just take on the coloring and shape of the rock. That wouldn't be that effective because they would have to sit completely still at the bottom of the ocean. No, the octopus dons all the appearance of the rock and then it moves very slowly across the ocean floor at the same rate of speed as the light moving in the water. So what looks like a rock with light playing over its surface of the rock is really an octopus in disguise sneaking up on some dumb crab.
  • Octopus mating is about as complex and involved as the rest of octopus behavior. When a male octopus woos a female octopus, he can use all sorts of techniques to get her attention. Some male species of octopus have stripes that become visible only when the male turns them on, so to speak, so he might flash his stripes at her. He might also puff himself up or even link arms with her.
  • Some sneakier males don't turn on their male stripe until they get really close to the female in her den. So they think the male is a female until he's right up next to her, and then he'll flash his male stripes not so much to get her attention but to keep other males from coming around.
  • When the male and female are ready for it, they move off together away from the den, holding hands. Or arms. Or tentacles. Then the actual mating can take place several times over. The male has a special arm called the hectocotylus which he extends and slips into the female's mantle cavity, where his octopus sperm gets deposited.

Octopus mating. He is inserting his hectocotylus into her mantle.
(Photo by Roy Caldwell, UC Berkeley)

  • After they're both satisfied, she goes back into her den and lays tens of thousands of eggs. The eggs are laid on strings which she weaves together into a kind of web and attaches to the ceiling of her den. She takes care of the eggs by blowing jets of water on them to keep them clean and warm.
  • She can't leave the den to get food, though. So she starves to death while the eggs grow. After about a month or two, the eggs hatch and the mother dies.
  • As for the father, usually he only lives a few months more after mating.
  • Depending on the species, an octopus may live only a few months or for a few years.

UPDATE 12/o9: Scientists recently revealed video of veined octopuses who live on exposed, sandy sea floors, picking up discarded coconut shells, tucking them skirt-like under their bodies, and running with them across the ocean floor. Once they get to a suitable place, they plunk down, pull the shell over themselves, and lurk in their new, convenient hiding spot. Or, if they've been lucky enough to find two halves of a shell together, the close the shell around their body and hide in there.

This article from the BBC has the video.

Smithsonian National Zoological Park, Cephalopods, Giant Pacific Octopus Behavior Watch, and Zoo Exhibit
Tree of Life, Cephalopoda
Joey C's Study of Octopus Behavior, Stone Middle School, Melbourne, Florida
Carl Zimmer, How Smart Is the Octopus?, June 23, 2008
Yasmin Anwar, "Octopus sex more sophisticated than arm-wrestling," UC Berkeley press release, March 31, 2008

1 comment:

  1. Some creatures are so ugly they're cute, but no stretch of my imagination can make an octopus even approach cuteness!


If you're a spammer, there's no point posting a comment. It will automatically get filtered out or deleted. Comments from real people, however, are always very welcome!