| eggshaped
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| 19099. Thu May 05, 2005 2:41 pm |
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This story must be useful – reminds me very much of a question in the last series (or probably the one before, seeing as I think it was about the angler-fish)
| Quote: | Australian and British marine biologists stumbled across the diminutive male octopus while scuba diving in the Great Barrier Reef. Divers spotted a male 2.4 centimeters (0.9 inches) long. By contrast, females of the species grow up to two meters (6.6 feet) long.
"Imagine a female the size of a person and the male a size of a walnut," said Tom Tregenza, an evolutionary biologist at the University of Leeds in England. Tregenza co-authored the study that reported the find in the latest issue of the New Zealand Journal of Marine and Freshwater Research.
"This is certainly the most dramatic example of sexual dimorphism in any large animal," said Tregenza. So-called sexually dimorphic species are those, like humans, whose males and females are of different average sizes.
Among their more unusual behavior, the octopuses employ a unique defense mechanism by tearing off the tentacles of passing Portuguese man-of-war jellyfish. The octopuses are immune to the tentacle's painful sting. When they encounter potential predators, the octopuses waft the captured man-of-war tentacles in two pairs of its upper arms as an effective deterrent. |
I’ve just posted a few paragraphs here, but I’d recommend reading the whole article. Fascinating.
http://news.nationalgeographic.com/news/2003/02/0212_030212_walnutoctopus.html |
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| Gray
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| 19106. Thu May 05, 2005 3:40 pm |
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| We could link this last fact to the boxer crabs doing effectively the same thing with the poisonous anemones, and, in the same Indiana Jones spirit, the fungus that catches nematode worms with its lasso. |
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| garrick92
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| 19455. Mon May 09, 2005 10:22 am |
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'Cephalopod' means 'head-foot', and they are so called because every cephalopod has a muscular foot that joins straight into its head.
The cephalopod that most of QI's viewers will be familiar with is the common garden snail. In snails, the muscular foot (which is replete with slime-generating bits, to help it glide along) is disk-like; in octopuses, squid and cuttlefish (and their odd relations, of whom more anon), the 'foot' is frilled out into arms and tentacles.
Here's a particularly handsome garden snail:
Some QI facts about the gardener's enemy.
Snails are hermaphrodites, being male and female simultaneously (well, that's probably the simplest way of putting it).
They have no jaws, but thousands of teeth. The garden snail has about 15,000. A snail's tongue is called a radula, and it is rather like the saw of a sawfish. Its teeth lie in rows along the tongue and the snail uses them to rasp away at the things it wants to eat. Here's a snail's tongue, close up:
Despite being hermaphrodites, snails have some extraordinary lurve-habits. When mating, snails fire arrows at each other.
Would-be snail-lovers circle each other for a period of time, and when they've made their minds up about whether it's a successful date or not they shoot each other through the genitals with whacking great darts. These are called love-darts.
Here's a picture of a speared snail:
The spear is the white pointy bit in the bottom right-hand corner of the image. As you can see, it's gone all the way through the snail and is poking out the side nearest the camera!
No-one's quite sure what the love-dart is for. The snails obviously enjoy it, so perhaps it's best not to ask. However, sundry voyeurs in white coats have determined that the dart may be for the purposes of letting (male) snail-spunk survive inside the (female) genitals of the receiving snail (who is also capable of darting a date). The reproductive tract of a snail is failry hostile to sperm, and the dart appears to suppress the digestive fluids that normally kill most of the sperm.
And here's the happy ending. Aaaahhhhhh..!
So, one question could be:
Q: Why doesn't Cupid call on randy snails?
A: Snails can fire their own arrows, thank you very much.
... and then you've got the stuff about hermaphrodism for extended chatter. And snails are, of course, a supposed aphrodisiac. Quite frankly, I find this unlikely in the extreme, but there you go. |
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| Flash
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| 19460. Mon May 09, 2005 10:40 am |
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| There's some great stuff on this thread. Can someone (eg Garrick) turn it into one or two questions with a summarised note to accompany, and post it on the "In Production" forum? Remember that we're trying to steer away from cryptic questions - ie the panellists need to know up front what topic they're supposed to be talking about. |
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| eggshaped
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| 19462. Mon May 09, 2005 10:41 am |
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| I may be jumping feet first into a subject I know very little about, but isn’t a snail a gastropod rather than a cephalopod? |
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| Gray
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| 19463. Mon May 09, 2005 10:45 am |
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Snails are gastropods, not cephalopods. (These two classes are both of the order Molluscs, but the only shelled cephalopod is the nautilus.
Nautili are fascinating, though - they only survived where the trilobytes didn't because of their scuba-gear. I'm going to open a thread on them... |
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| garrick92
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| 19469. Mon May 09, 2005 10:59 am |
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| You're quite right -- gastropods they are. What a dildo I am. Kindly ignore everything I have typed while I crawl away to die of embarrassment. |
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| Gray
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| 19483. Mon May 09, 2005 11:23 am |
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| Nice work, though, and I don't see why we can't save it under C for Cupid (seeing as we have that statue of Not-Eros as a question too). |
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| eggshaped
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| 19496. Mon May 09, 2005 11:50 am |
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| What about C for Copulation? There must be enough material in the animal world for a full series. Then again, there is the watershed… |
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| Jenny
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| 19544. Mon May 09, 2005 3:46 pm |
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| Cupid is satisfactorily pre-watershed. |
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| Jenny
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| 19552. Mon May 09, 2005 3:55 pm |
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Another interesting thing about snails is that they have green blood due to haemocyanin (contains copper rather than iron).
http://www.anu.edu.au/BoZo/backwell4/mollusca.htm
On that same link - more QI stuff about cephalopods:
| Quote: | Predatory carnivores. Prey caught in arms (suckers); horny beak-like jaws first, then radula. Many = poison in salivary glands. Octopus mainly eat crabs and clams. Squid eat mainly fish and anything else they can catch.
They have large, lobed brains with millions of nerve cells in a cartilage cranium (brain case). Largest of all invertebrates. Chemoreceptors and machano-receptors on tentacles = feel and "taste" well. They don’t hear but good vision. Convergent evolution with vertebrate eye: Iris, retina, cornea, lens. They can control the amount of light that enters their eyes (we can’t), they can focus, see colour, and visual acuity greater than ours cause retina is of much finer structure.
Ink sac in some : opens into the rectum, contains sepia intermixed with mucous. Not blocking view, works as "dummy" |
I didn't know some octopi were poisonous. I love the idea that they can taste their food with their tentacles. And I particularly like the idea that some of them fart their ink at people from whom they are trying to escape, though possibly my amusement at this latter is due to my childish sense of humour. |
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| Gray
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| 19573. Mon May 09, 2005 4:40 pm |
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| Quote: | | They can control the amount of light that enters their eyes (we can’t) |
Isn't that what our irises are for? If the suggestion is that we can't do it 'involuntarily', which is correct, then it remains to be seen whether the cephalopods have 'voluntary control' (which must be impossible to know, surely). |
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| eggshaped
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| 19704. Tue May 10, 2005 2:17 pm |
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A cephalopod who is the master of disguise…
| Quote: | The clever creature is a brown octopus about two feet (60 centimeters) long that slithers along the muddy bottom of shallow, tropical estuaries where rivers spill into the sea. It was discovered so recently that it still doesn't have a scientific name, but scientists are intrigued by its uncanny ability to impersonate lion fish, soles, and banded sea snakes.
Octopuses are thought to be one of the most intelligent invertebrates and can change the color and texture of their skin to blend in with rocks, algae, or coral to avoid predators. But until now, an octopus with the ability to actually assume the appearance of another animal had never been observed.
Mimicry is a fairly common survival strategy in nature. Certain flies, for example, assume the black and yellow stripes of bees as a warning to potential predators. But the adaptable octopus is the first known species that can assume multiple guises.
Each of the nine specimens that scientists saw during research dives off the coasts of Sulawesi and Bali in Indonesia impersonated more than one toxic species. The creatures they routinely mimicked were:
• Sole fish. To take on the appearance of flat and poisonous sole fish abundant in the habitat, the octopus builds up speed through jet propulsion and draws all of its arms together to form a leaf-shaped wedge. It then undulates in the manner of a swimming flat fish.
• Lion fish. Just above the seafloor the octopus swims with its arms spread wide and trailing from its body, mimicking the lion fish and its poisonous fins.
• Sea snakes. Changing its color to imitate the yellow and black bands of the toxic sea snake, the octopus threads six of its arms into a hole and waves the other two arms in opposite directions so they look like two snakes.
The researchers think the octopus also may be able to impersonate other sea creatures such as sand anemones, stingrays, mantis shrimp, and jellyfish. For now, however, the scientists will only say for sure that the octopus can mimic sole, lion fish, and sea snakes. |
http://news.nationalgeographic.com/news/2001/09/0920_octopusmimic.html |
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| Gray
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| 25166. Wed Sep 28, 2005 2:44 pm |
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Giant squid caught on film
ABC News
Aljazeera (with a picture...) |
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| Caradoc
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| 25174. Wed Sep 28, 2005 5:01 pm |
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| I like the Aljazeera picture with the finger to show actual size |
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