How big do you think that a giant cephalopod can get?

[OB]

As Carl Popper taught us; nothing is true, nothing is even likely, things are, at best, not unlikely, so scientific "truth" is never gospel (nor is gospel, for that matter ) and facts are by their nature subjective experiences. It will, however, require quite a bit of a stretch to see an giant or colossal squid live beyond its normal lifespan of maybe two years, let's give it three. One mutation won't be enough, and the chances of the five or six potentially required all happening at once maybe a lot slimmer than the admittedly vast number of squid even allows. This is "gut feeling", not fact. In my wildest imagination I can still picture a 3 or 4 meter ML squid, maybe even an as yet undiscovered species of that size (what on earth would "humongous squid" live off, colossal squid? Sleeper sharks?), but it remains pure speculation. Imagining a viable ecosystem at depth in the ocean with a ridiculously large squid (as in; exceeding 4 meters of ML) requires a long, long stretch, filled with as yet unsustainable assumptions. A surface dwelling monster would have to be spotted more than often, as it would need to maintain a breeding population comparable to other invertebrates.

On a final note, just a thought: the feeding habits of squid are limited by the diameter of its oesophagus, limited in turn by the "need" for it to pass through the brain (i.e.: "Stupid Design"). I should do some calculations, but you could well get to a point where the bulk of a squid becomes unsustainable as it would not be able to gulp down sufficient amounts of small bites in a row, given the available prey items and their average size.

 

[Level_Head]

On a final note, just a thought: the feeding habits of squid are limited by the diameter of its oesophagus, limited in turn by the "need" for it to pass through the brain (i.e.: "Stupid Design"). I should do some calculations, but you could well get to a point where the bulk of a squid becomes unsustainable as it would not be able to gulp down sufficient amounts of small bites in a row, given the available prey items and their average size.

There's a problem with cephalopod-kind
That's unique among things with big brains
What he's eating must go through his mind
And the thought of it might give him pains

But this problem is seen when quite small
So the limits we pick still could be low
Would we guess in the hundreds at all
If we'd only seen squid at one kilo?

 

[ScottDV]

On life spans to take us as an example to compare with. The life expectancy of an American male is 75 years old. I took a call from a person reporting the death of their father at my work who died a month after his 110 birthday. Also the oldest man on record was over 120 years old. There may have been older men in previous ages but most nations did not keep records of birth for people unless they were very important such as royalty. Those people have BOTH genes for longevity, passed from the father AND Mother's side to make them live, extra, extra long. So there may be some very rare cases of squids who likewise have the rare combinations of genes and long lives to get really, really big.

 

[ScottDV]

This is an entertaining discussion. I am not arguing there is a giant squid out there over 100 feet long 9counting tentacles and arms) but just stating that until we know more about the other 95% of the ocean and the diversity of life of those deep biomes in the inky black depth miles below the surface we cannot categorically deny the possibility that one might exist either.

Do we actually have a large enough baseline sample of carcasses to get a real idea what the average size range of an adult giant squid is? How many squid bodies do we have an 'officially' measured over the past 100 years or so?

 

[Damien]

About that point I suppose that several researchers around the world are maybe trying actually to use similar methods that Mr KUBODERA did to catch giant or colossal squids pictures.

More than the scars, the beaks are a good mean to evaluate size because and from statistic point of view the fact that we hunted sperm whales in huge quantity is a good argue.

 

[Tintenfisch]

Yes - the maximum size estimates for large squids are not generally based on just the officially measured whole carcasses known to science. They are based on the range of beak sizes known from the stomachs of their predators - which are far more efficient at sampling squid than humans are. Using the sizes of the beaks in the whole specimens for comparison, we believe that a reasonable estimate of maximum size can be made from the larger beaks found in whale stomachs. In the Antarctic, where Mesonychoteuthis comprises 77% of the sperm whale's diet by weight, it seems like a safe-ish bet that the sperm whale stomachs examined will hold a reasonable range of the available squid sizes. One can always speculate about squid that grow too large for whales to sample being 'off the radar' for this method, but in the absence of any evidence, such speculations seem unwise (however fun to imagine).

 

[neurobadger]

My two cents is that since it doesn't have the structural support of the blue whale, it can't get bigger than 100 feet in mantle length.

If you added arm and tentacle length, though, since one doesn't have to worry about gravity, they could theoretically grow infinitely long, but it would have to be commensurate with the amount of energy an animal could expend pumping blood and moving arms and tentacles that long.

 

[Level_Head]

I'd be interested to see the calculation where the result points to a hundred-foot (or thirty-meter) mantle length.

Instead of saying: "since it doesn't have the structural support of the blue whale, it can't get bigger than 100 feet in mantle length" one could almost say "since it doesn't need the structural support of the blue whale, that isn't the practical limit on mantle length."

I don't know what the practical limit is. There are oxygen transport issues; such a large creature would need compromises including very low levels of activity. I can imagine a sort of floating island, dragging the occasional too-close large fish or sea mammal to its doom but otherwise exhibiting little movement.

But if there are formulae that suggest maximum sizes, I'd like to see them! Some of the ideas offered, like the "throat-through-the-brain" bit, don't seem to prevent sizes spanning three orders of magnitude. Perhaps the limits are elsewhere.

Practical limits are a different thing, and I expect that extant colossals and giants don't much exceed what we've seen.

 

[neurobadger]

To be honest, Level_Head, I pulled that one out of my arse, but formulae for cetacean size might be an indication. I don't think formulae for vertebrate mechanics would help, since they operate under gravity and with a skeleton.

The ocean is essentially a zero-gravity environment externally, so that is not a constraint as long as buoyancy is maintained.

It would probably depend on the family of squid; the colossal squid, as many cranchiids, is suspected to put its arms and tentacles upward as it rests, because it cannot see around it any other way, and this may affect arm and tentacle length. Too large of an arm or tentacle would prohibit oxygen from reaching all of the cells, similarly to the necks of some dinosaurs, which were suspected to be too long to hold upright, else the animal would asphyxiate.

Animals such as ommastrephids and loliginids do not need to hold their arms up, which would probably not limit the length of their arms.

Oxygen transport hasn't seemed to be an issue for the blue whale, and it has more mass. It also has one heart.

Since it's ectothermic, it would have a far slower metabolism, although I don't know if that would impact body size.

I'm using the example of the blue whale since it has a metric f-ton of body mass in addition to long length; perhaps estimates of sauropod size would be better (200 feet).

 

[Level_Head]

I expected as much, though I wasn't sure of the source cavity or aperture. ]

Nevertheless, that single heart is assisted by muscular pumping in body tissues, as well as many adaptations specific to cetaceans. I do not know where to start for size limits on a giant hydrostat-muscled fairly energetic mollusk.

I just recalled that there is a very large cephalalopod -- biologically engineered and in a sea without some of its natural predators -- that figures into this webcomic story. Here's the first image of the critter:
Saturday 5 November 2005

And here's the story itself:
Sunday 2 October 2005

(But I'd start from the very beginning. It's an excellent strip.)

 

[DWhatley]

Up to Dec 26,2005. Must stop. Have other things I NEED to do tonight ...

I particularly identify with this one: Saturday 31 December 2005

I must get back to what I need to do ...
Read this guy for awhile have you, Level_Loo? Monday 25 September 2006

 

[Firefly]

Nice debate here.
Thanks for all your replies.

 

[Level_Head]

Up to Dec 26,2005. Must stop. Have other things I NEED to do tonight ...

I particularly identify with this one: Saturday 31 December 2005

I must get back to what I need to do ...
Read this guy for awhile have you, Level_Loo? Monday 25 September 2006

Oho! I missed your post for a while. Yes, there is a connection there. And here, on the following page:
21st Century Fox: Archive for Wednesday , July 14 , 2004

And here:
Magpie House Design - Carry On

But Schlock Mercenary links back the other way, too, as you probably saw -- in this footnote:
http://new.schlockmercenary.com/d/20060122.html

 

[DWhatley]

Level_Loo
Somehow you lost me on what I should see in the links. Ah, I see the connection now


I was all caught up with Schlock but have not gone back since. I wish I could get a daily email.

Went back to catch up and it now ends on October 26th. That story ended and he created some updated character changes when I last read but the site seems to have issues. Did he move without a forwarding address?

 

[Level_Head]

Ah. Off topic, it was -- I was featured as a character in each of those strips (although in one case the "character" was that of a comet). But back to our topic at hand:

The common suggestion that a giant or colossal squid leads a largely sedentary lifestyle -- grabbing the occasional fish, but with many days or weeks passing between meals -- makes me think that a cephalopod could in principle get much larger. Keeping brain size small to reduce energy requirements (as does the lifestyle) means that more of the oxygenation can be delivered to other tissues. Cephalopods have a pretty good circulatory system as it is, an active, high-pressure, closed system very unlike other mollusks.

Assuming a creature content to laze about, and not think too deeply, a theoretical maximum seems to be much higher than what we've seen.

Not that such creatures likely exist -- sperm whales have done too good a job of collecting beaks -- and we've done too good a job of collecting them -- for any high probability of remaining monster squid. Or so it seems to me.