On cranchiid feeding posture

[OB]

I came accross this interesting set of stills of (most likely) Helicocranchia sp., taken on 31 march 2003 by the MBARI Gulf of California expedition (Cerralvo Trough). It shows the squid in a position as postulated by SOS for Mesonychoteuthis. I found this to be a nice bit of supporting evidence

 

[main_board]

Man cranchiids are wierd! So many of them look alien, more like a jellyfish and their kin than any sort of cephalopod. Great pictures though! Where are the threads on which Steve talks about the messie positioning? I don't remember reading those.

Cheers!

 

[OB]

Urrrr, let me think. It wasn't so much a focussed thread per se, more a remark in one or two of them, alluding to a "position paper" on M. hamiltonii postion.... Maybe Steve could illuminate the current status of the paper, perhaps it's still under peer review?

PS: this is what's commonly known as the Cockatoo position, a bit like the J posture, gone horribly wrong

 

[Phil]

I believe this passive-drift mode has been dubbed the 'cockatoo posture', and (I think) is peculiar to cranchiids. I'm sure I've read that the giant Megalocranchia has been observed doing this too. I'm not sure what advantage is to be gained from drifting so other than energy conservation. Maybe such crachiids tend to strike from below and this is passive - but prepared - behaviour?

(Edit, oops, sorry ob, didn't mean to repeat you. Must read before I leap in future....)

 

[Clem]

Hi,

Apologies if it was posted and discussed elsewhere, but this link still ought to be in this thread:Helicocranchia, The Piglet Squid (The image is part of a photo gallery; click the lower right square.) Many features of interest to peer at, and the piglet gag always makes me laugh. In addition, there's a different shot (lower angle) at the online New Scientist from July of 2006.

Cheers,
Adam

 

[fluffysquid]

piglett squid!!!! eeeeeee! that made my day.

 

[Steve O'Shea]

Whether the squid hold the arms up or down probably depends on the arm formula; those with the dorsal arms shortest (of the 4 pairs)probably hold them up (all arms), whereas those with the dorsal arms longest hold the arm crown down; that's the theory - I'd love to put it to the test. It probably wouldn't take much to do.

 

[Tintenfisch]

Taonius does it too - see the pic on the Cephalopods in Action page, which is a still from the T. pavo video on this page. There's a video of Teuthowenia doing the cockatoo (too).

 

[Clem]

Taonius does it too - see the pic on the Cephalopods in Action page, which is a still from the T. pavo video on this page.

...and below, another Taonian, from MBARI rov footage. Adoption of the cockatoo posture seems to allow the eyes to move forward and closer together...improved depth perception? Useful for targeting prey and judging distance from intrusive cameras... What's the evidence that the posture is related to feeding? Direct observations in the wild or a cranchiid specimen in a holding tank? I can see how it could work, just curious to know the facts.

Cheers,
Clem

 

[tonmo]

That is truly weird, and equally cool...