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Why is the Giant Squid so giant?

Steve O'Shea

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What a buzz :grad: I just learnt something (not that there's any surprise there). Very similar to Octopoteuthis in overall appearance (though in different families) is a genus called Ancistrocheirus; they're not very common at all (as adults - I might have a half dozen specimens), and like Octopoteuthis they posess two rows of seriously evil hooks along their arms; they differ (in a number of respects) most notably in that the genus retains the tentacles in the adult (and the tentacles are large and well formed - although none that I have is complete - I do in the juveniles though).

Either side of each row of hooks is a very fleshy and extensive membrane. The membranes on either side fold together and enclose the hooks within a groove, thus, possibly, protecting the delicate tentacle from snaring itself. The membrane is called (surprise surprise) a 'protective membrane'. The same 'protective membranes' are very well-developed in enoploteuthid squids also.

They've obviously been called 'protective membranes' for a good reason, so someone must have demonstrated their value/function before (so we just re-invented the wheel .... don't you hate that), but their function had never really dawned on me before (that they are extremely well developed in genera/species that possess both hooks on the arms and have long/functional tentacles) - it was just a name given to a structure in accordance with some illustration I'd seen. Not to worry (nobody ever taught me this so there may be a few others out there that don't know either).
Cheers
O
 

Phil

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Thanks again, Steve.

'Protective Membrane', there's imagination for you! On the other hand, it's good to hear a term that is easily understandable instead of some convoluted Latin derivation. Imagine if a German researcher had named it!

Just a thought, but if Architeuthis hangs in the water column with the two main tentacles hanging loose and spread wide as with Mastigoteuthis, then would it really need to have this arrangement whereby the two main tentacles could lock together using its toothed suckers? It seems to me to be a more efficient arrangement to spread the net wider if the creature is not an ambush predator, implying that this ability to lock the tentacles together could be seen as a redundant feature. Yet Architeuthis has poor musculature and is thought to be a poor swimmer. It’s all very confusing!

It was very interesting your observation that the tentacles in Nototodarus function almost like a sighting arrangement on a rifle, could one assume Architeuthis uses its tentacles in a similar fashion? It would explain why the tentacles could be locked together. I suppose a similarity in general form (i.e exceptional length) to the tentacles in Mastigoteuthis and Chiroteuthis does not necessarily imply a similarity in function. Also, Chiroteuthis has a light organ at the tips of its tentacles whereas Architeuthis does not, implying a different feeding action.

I’m speculating but if Architeuthis does indeed use its tentacles in a similar manner to Nototodarus then Architeuthis would not necessarily be at a disadvantage due to its poor musculature as prey at Architeuthis’ normal depths is, (please correct me!), much slower moving.

I’m not sure I’m making much sense as I’m thinking this through as I write!

Thanks,
Phil
 

Steve O'Shea

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Phil said:
It was very interesting your observation that the tentacles in Nototodarus function almost like a sighting arrangement on a rifle, could one assume Architeuthis uses its tentacles in a similar fashion? It would explain why the tentacles could be locked together. I suppose a similarity in general form (i.e exceptional length) to the tentacles in Mastigoteuthis and Chiroteuthis does not necessarily imply a similarity in function. Also, Chiroteuthis has a light organ at the tips of its tentacles whereas Architeuthis does not, implying a different feeding action.
Phil
If ever fortunate enough to see an Architeuthis with all of its skin intact (a marvelous sight) you will notice that the animal is dark red on every body surface, except two: the inner face of the tentacles themselves (light pink), which have the 'knob/sucker' arrangement that lock into an opposing sucker/knob on the other tentacle; and the inner face of the tentacle clubs (which is porcelaineous white).

In addition to the inner face of the tentacles being flattened [indicating they would be clasped together], it is coarse, beset with innumerable minute bumps. These would provide a non-slippery surface, assisting the suckers and knobs in locking the two tentacles together.

Indeed Chiroteuthis has the photophore at the very tip of the tentacles, but Architeuthis has those enormous eyes and brilliant white inner face of the tentacle clubs. I have no doubt that the adult could see them in the distance (the inner face is in stark contrast to the outer side of the tentacle clubs, which is a very dark red (in fact, darker than the skin of the mantle and head)).

Clasped together the two anaconda-like tentacles of Architeuthis likely writhe their way through the dark in search of prey. The prey (fish) would be sought out and grasped between the two tong-like clubs, then either slowly withdrawn (struggling) to the arms, OR the squid would lunge forward and restrain it with the arms. Of course 'lunging forward' is not going to go unnoticed, but these schools of fish (hoki) are extremely dense and widespread (hence their being a major fishery target); probably a scattering of fish one minute would be compensated by an influx of others the next (I think the forward lunge to be far more likely than the retraction of elastic tentacles).

That's my theory anyway ... I guess we'll all just have to wait and see whether there's any truth in it. Exactly how Chiroteuthis feeds is another matter altogether; there may be some interesting submersible observations here that could help answer this question.
Cheers
O
 

Anonymous

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Not to change the subject of the original post but does the dark red coloration of Architeuthis also extend to the suckers on the arms :?: For some reason I got it in my head that they were pinkish. I know it's nit-picking but I am painting a model of Architeuthis and would like to be as accurate as possible. Sounds like one can get the job done with dark red, white, pink and black (for the eye and beak). Wrong? Right? In any case I feel I'm getting closer after my original job of light grey overall :oops: Thanks for the insight!
 

Nancy

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Not to change the subject, but where did you find a model of Architeuthis?
Or did you make it yourself? :squid:

Nancy
 

Steve O'Shea

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Just a quicky, but the suckers on Architeuthis are brilliant white, and the flattened inner face of the arms is slightly lighter in colour than the outer convex face of the arms (so pink as opposed to red would be a good colour).

....and following on from Nancy's question, how big is this model you are making, and what are you making it out of? Very interesting.
Cheers
O
 

Anonymous

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Thanks Steve! In answer to your and Nancy's question I am currently working on a shadowbox deplicting Architeuthis and are using pre-made squid figures that I have found here and there. The ones I have are as follows:

(1) An eighteen inch rubberlike figure made by Safarai Ltd. and available from http://www.linkandpinhobbies.com/dinotoys.html

(2) Small plastic figure made by MPC Plastics and out of production.

(3) Six inch lead figure made by RAFM Minatures and also out of production (perfect for Phil's Nemo vs Kraken game).

In spite of my lack of artistic talent I do plan on handcrafting larger versions out of hydrostone and papier-mache and do want to be as accurate as possible although nothing as large as the life size figure my wife and I made out of snow last winter complete with red dye and paper plates for eyes (not a lot to do out here in Nebraska in the winter :roll: ) As enraptured as I am with Archi, I am spellbound by Mesonychoteuthis hamiltoni . . . . . . maybe a future model? Sorry this got off the intended topic (which was fascinating by the way) but I wanted to answer the questions directly. Salutations from the self-proclaimed squid capital of Nebraska! 8)
 

Tintenfisch

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OMG, Snow Squid!!! That takes the prize for coolest snow creation... I made a huge kiwi bird once, but I think Archisnowthis wins arms down. Too bad there's not much white stuff at the moment for such divertments, eh. :wink:
And oh yes, Omaha is DEFINTELY the squid capital of Nebraska. 8)
 

Steve O'Shea

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Just checked out the hooks on the arms on a fresh-fixed Taningia that came in today (in overall facies very similar to Ancistrocheirus, the animal that had the extremely well-developed protective membranes running either side of its hooks, and with substantial tentacles), and Taningia (which lacks the tentacles in the adult) lacks the protective membranes either side of its hooks.

Very very interesting! One could leap to the conclusion that those membranes prevent the tentacles from becoming snared by their very own arm hooks; any other suggestions?
O
 
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Hi,

Just wanted to throw my two cents in about the definitions posted earlier. My herpetology intsructor said that paedomorphosis as it pertained to the axlotl meant that the juvenile form could take one of two paths: an adult form (without gills), or the juvenile-looking (with gills) form. In other words, there is a "choice" of sorts (probably depending on the environment, hormones, and a few other factors.)

He also went on to say that neoteny is based more on ontongeny recapitulating juvenile characteristics as a rule, i.e., that the neoteny is present in all individuals as part of its evolutionary lineage. For example, we humans all tend to look like neotenic hominid young (large heads, roundish bodies, etc.).

These might not be exact definitions, as I think he went on to mention that these defs. were "close enough for government work". :roll: I hope this helps.

Getting back to the original topic here, just how big is the theoretical limit on the size of an Archi? If there was some mega-archi back some time ago, like my favorite mega "Jurassic Shark" Carcharadon megalodon (sp?) then, by crickey!... this thing must have been a massive hunk of squiddage!

Sushi and Sake,

John
 

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