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Cthulhu: the early years - Input Junkie
July 17th, 2011
08:31 am


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Cthulhu: the early years
A Nova program about three species of cuttlefish:

The broadclub cuttlefish strobes (fast moving bands of white and color) in order to confuse the small crustaceans it hunts. It might take quite a while to evolve something that can drive humans to insanity, but considering how many cuttlefish are eaten by humans, there's motivation. Also, the cuttlefish can practice on dolphins, which are also a species enemy.

The giant (up to 3 feet long-- almost a meter) Australian cuttlefish exists to annoy evolutionary psychologists, or at least I like to think so. The larger males do flashy displays to attract females, try to keep other males away, and sometimes wrestle with each other. The females look bored. [1]

Female cuttlefish have a lot more choice than females in any other species I can think of. Not only does the male use his tentacles to hand his sperm to her, but then she stores the sperm under her tentacles, and chooses which sperm to implant.

Smaller males use a different strategy than the big guys. They can dodge in under the males who are doing the big displays, while camoflaging to look pretty much like females. Females show a strong preference for the sperm from the stealth guys.

I'm thinking about why the little males haven't completely out-bred the big males. Perhaps size offers an advantage against predation, so there's a balance.

From the transcript:
One of the biggest surprises is that the cross-dressing males got the very next fertilization. And we did not expect this at all. The only reason we could think of is that this is a very bold, smart tactic. And the females may be acknowledging that in, sort of, evolutionary terms. So this trick, as strange as it seems, is very successful.

I'm inclined to think the females prefer males who actually spend time with them.

The third species is the flamboyant cuttlefish. It and the mimic octopus live in mud flats off the coast of Indonesia, a very tough environment because there's no cover. [2] The flamboyant cuttlefish is only two inches long, does a flashy (but non-strobing) display when threatened, and walks along the bottom with as much attitude as a skunk. It turns out that its flesh is poisonous, with a poison previously unknown to science. I suppose no one knows yet how it keeps from poisoning itself.

People don't know how smart cuttlefish are, but they're surprisingly bright.

[1]I'm reminded of all those nature specials showing mountain rams madly bashing heads, while the harems of ewes stand around in postures of unutterable boredom. They'll get the good genes regardless; they don't have to care. --Bujold.

[2] Is there any sf about the evolutionary consequences of environments without cover?

Initial link thanks to james_nicoll.

This entry was posted at http://nancylebov.dreamwidth.org/489975.html. Comments are welcome here or there. comment count unavailable comments so far on that entry.

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(4 comments | Leave a comment)

[User Picture]
Date:July 17th, 2011 06:49 pm (UTC)
Why would the Australian cuttlefish annoy evolutionary psychologists? Don't evo psych types already argue that men engage in status competition to attract mates?
[User Picture]
Date:July 17th, 2011 07:42 pm (UTC)
Winning status competitions doesn't seem to be the most obvious route to successful reproduction for males.

It isn't obvious why the males pretending to be females don't end up fighting each other. Maybe relatively few manage to succeed at sneaking close to the females?
[User Picture]
Date:July 17th, 2011 10:42 pm (UTC)
Oh, wait. Somehow, I read the first two paragraphs, thought to write my comment, went on to read the rest of the post, and then the rest of the post fell out of my brain and I went back and wrote my comment.

Anyway, yeah, the real mystery (I think) is how do the cuttlefish keep from breeding themselves for smallness. Maybe the females' sexual preferences change depending on how many big males are around? Too few, and they start lusting after bigness; too many and the little guys start to look attractive again.
[User Picture]
Date:July 17th, 2011 11:14 pm (UTC)
Maybe medium-sized cuttlefish do worst-- too big to pass for female, and too small to win mating fights.

Maybe the cuttlefish are speciating, and there will eventually be distinct large-male and small-male species.
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