Colossal Squid Necropsy

Steve O'Shea

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This should have aired on Discovery Channel News (Canada) a week-or-so ago; we've yet to receive copies so don't know what the final product looked like.

Cheers
Us
 

Bald Evil

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Steve talks like Phantom...Ghost Who Walks...the Marine Biologist Who Cannot Die...

So much for your secret identity!
 

Steve O'Shea

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I am but a figment of your imagination. My real name is Paul.
 

myopsida

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No, but I saw Steve the other day - almost as good as the real thing!
 

Steve O'Shea

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Paul will be in Wellington again in a couple of weeks to check out the flounder collections; will make it for a Friday bev. ; I'll be the one in the red lycra suit. Gotta check out those cranchiid collections to see whether there's any juvenile Mesonychoteuthis from NZ/proxim waters, and octopoteuthid collections to finish off two more MS's. Both are proving to be real cans of worms.
 

Steve O'Shea

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Jean said:
Can either Steve or Kat tell me? Is the inner mantle really black?? Or was it ink? or an artifact of filming? J
A frightening thing just occurred to me (have just woken up, so must have been thinking about this). The standard theory is that the inner wall of the mantle is dark, in the case of Mesonychoteuthis, black, to shield light from bioluminescent prey in the squid's stomach/stomach caecum from shining through the mantle, identifying the squid to potential predators.

Other than the sperm whale (I'm not sure whether the whale uses eyesight or sonar to locate prey), what possible predator could there be down there that would take on a full-grown colossal squid? :goofysca: :goofysca:

There must be another reason for the dark-pigmented inner-mantle wall of the colossal squid (it is this or there is something even more formidable down there ..... shudder!). Prey (as in Patagonian Toothfish), don't bioluminesce (as far as I know), so the dark inner-mantle wall probably doesn't serve to conceal the squid from potential prey .....

Something weird is going on. Anyone with any suggestions?
 

Steve O'Shea

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Having given this 2 coffee's worth of consideration I have come up with 2 suggestions:

1) Cranchiid squid like Teuthowenia can pull their head entirely within their mantle, inking within the mantle and appearing like grapes (this is actually what I thought we had in one sample several years ago - deep-sea 'grapes'). As the eyes of Mesonychoteuthis have photophores, perhaps this animal can also withdraw the head (and arms) within the mantle ... ouch ... and the black lining of the mantle wall conceals any bioluminescence from the eyes. You still have to have a large-enough predator to warrant this behaviour, however. Perhaps the smaller animals need to be able to do so, and the character state is just carried forth through to the adult (where it isn't really required, but is a non-lethal behavioural attribute ... as in it doesn't harm the animal to be able to do so, rather than it being advantageous to be able to do so).

2) The ink is bioluminescent .... and for the same reasons as above, this character state is retained by the adult, and is a non-lethal condition.

Any further suggestions?
 

Clem

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Steve,

Don't know how effective head retraction would be in eliminating the light signature from the photophores, but I don't know what Mesonychoteuthis' orientation in the water column might be (I'm waiting on "the theory":wink:). Unless the seal between head and mantle was very tight, you'd still see a cylindrical shaft of light emanating from around the retracted head. If Mesonycho held its head down, that leakage would probably not draw diving predators, but...I'd also worry about damage to the eyes incurred during a fast, emergency retraction. Ouch is right.

I'd think that cupping the eye with a looped tentacle would be about as effective at masking the ocular light organs. Can Mesonycho stretch its arms and inter-arm web up high enough to hide the eyes, ala Vampyro?

If the "stealth lining" theory is correct, perhaps it was most useful back when there were 12-meter, apex-predator sharks to worry about.

:roll:

Clem
 



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