Colossal Squid Necropsy

Phil said:
I have read that sperm whales do not tend to feed on surface cephalopod species even though they often abound in the same feeding grounds, which strikes me as somewhat odd, so perhaps the presence of Mesonychoteuthis in surface waters is a survival strategy in itself.

Phil,

Now, that's an intriguing thought. A pod of diving whales would generate a mass of echo-locating "cones," widening and converging as the pulses move deeper and away from the whales' heads. The deeper a prey item lives, the better the chances it will be visible in the return. If Mesonychoteuthis were closer to the surface, its chances of escaping detection might be improved.

On the other hand, the ratio of Mesonychoteuthis beaks to Architeuthis beaks in whales' stomachs would suggest that the Colossal has some disadvantage that no amount of light-signature moderation or vertical movement can overcome. We're both waiting on "The Theory" of Mesonycho's attitude in the water, but I'd guess it was generally horizontal, with the tail and arms angled slightly downward from the fulcrum point of the head. If so, that may be its Achilles heel vis sperm whales.

A horizontal Mesonychoteuthis would reflect a much larger sonar image to a diving whale than a squid hanging at 45º would; presenting an end-on view with a smaller sonar cross-section (and significantly less dense tissue composition) might have given Architeuthis an edge, if it's comparatively lesser place in the sperm whale's diet is any indication. As you say, maybe Mesonychoteuthis reacts to being "painted" sonically by rotating to a vertical position and putting out the lights, keeping still and ready to fight.

As for killer whales, you've got me good and stumped.

:|

Clem
 
Clem and Phil:

Check out this link:

http://www.cetacea.org/orca.htm

Orcas are pretty much mammalian sharks with a brain. I wouldn't be surprised to see hem eat relatively large species of squid (Dosidicus, maybe the occasional hapless Moroteuthis, Taningia, etc.). Apparently there is evidence, just no one seems to have recorded just WHAT species were eaten.

If I find more, I'll let you know.

Sushi and Sake,

John
 
If I may humbly ask a question, do we have any conclusions as to the growth rate and age of the 2003 specimen following examination of the statolith?
 
I believe the statolith(s?) went to a colleague of ours who does some work on them, and I haven't heard anything further, but it would be good to follow that up...
 
Thanks Kat, I'll watch this space.

I have a vague three -four year thing grumbling at the back of my mind, so that's bound to be way out!
 
Steve O'Shea;8683 said:
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).
...elsewhere in the forums ob brought up the 1981 Meso specimen caught by a Russian trawl. We were discussing Mesonychoteuthis eyes. The '81 squid's eyes look very well-preserved...which is amazing, when you consider that the squid was trawled. The mantle and arms look as banged-up as you'd expect, but the visible portion of the head hasn't suffered nearly so much abuse. Trying to account for the high level of preservation of the most delicate parts, I recalled Steve's earlier post. The photo of the '81 Meso suggests to me that large sub-adults are capable of retracting the head into the mantle cavity, and that's what this squid did when the trawl hit it.

Thoughts?

Clem
 

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cuttlegirl;88872 said:
Hmmmm... which might explain why the head looks so much smaller than the mantle, because it has to fit inside the mantle.

I agree. And looking at this photo with the latest discovery in mind, the head does look quite smaller than the mantle. I never really noticed that before.
Interesting stuff!
 
rather interresting stuff here. something that kept occurring to me was that the reason for "cloaking capability" might well be courtship related,and that rather than some fearsome as of yet unknown predator the culprit was more likely members of it's own species. just a thought.
 
in the case of it being a courtship related issue,what i'm getting at is the possibility of rival males needing to escape one another when they are outmatched.

but something else occured to me while researching humboldts the other day...cannibalism. don't know if there's been any evidence in the stomachs of necropsied messies,but i'd run across an artice out there somewhere stating that in 1999 a tasmanian archi turned up with tentacle fragments in it's belly.

just shooting in the dark here.
thought i'd share and all that.
 
ubiquity;89053 said:
in the case of it being a courtship related issue,what i'm getting at is the possibility of rival males needing to escape one another when they are outmatched.
Hi Ubiquity,

That makes sense if the mantle of the cranchiid in question is transparent/translucent at the age of sexual maturity, and we do see that feature in smaller cranch squid. A grown Mesonychoteuthis's mantle is thick and opaque, and has a black-stained inner lining to boot, so inking inside itself may not have an appreciable benefit. It would be beneficial in the early stages of Meso's life, when it is more clear-bodied and vulnerable to a wider variety of would-be predators, including other squid. But, maybe I've been making an assumption about the self-inking being deliberate in the first place. Is it possible that it's involuntary, a consequence of the squid turning itself into a ball?

Cheers,
Clem
 
howdy clem! :smile:

involuntary?

you really think so?
...what's leading you to this conclusion?

and by the by it's good to be back. haven't had a chance to keep up with you guys in quite some time.
 
ubiquity;89053 said:
but something else occured to me while researching humboldts the other day...cannibalism. don't know if there's been any evidence in the stomachs of necropsied messies,but i'd run across an artice out there somewhere stating that in 1999 a tasmanian archi turned up with tentacle fragments in it's belly.

Hi Ubiquity. We put a paper out on this very thing in 2004 (NZ Journal of Zoology I recall). There's a version of it online here, although I do note some corruption in some of the characters (if you want a pdf of the paper just pm me). The Zeidler & Gowlett-Holmes paper to which you refer (from Tasmania) didn't attribute the sucker rings in the stomach caecum of Architeuthis as belonging to Architeuthis, but they were certainly of a size consistent with them. There has been a further, more recent paper recording cannibalism in Architeuthis, based on genetic screening of stomach contents, so it doesn't appear to be too infrequent in occurence.
 
I'm afraid I can't chime in with regards to Russian trawl Meso's headsize, it's actually just slightly smaller than the mantle opening, but there's a notable "constriction" between the massive eyes and the posterior portion of the head.

Was this specimen's ML determined at all?
 
thanks for the link steve!
a good read for sure and very informative.

needless to say it has my wheels spinning.
so,..
any evidence of cannibalism in messies yet?
 

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