Calcium Content in Cephalopods

Pr0teusUnbound

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#1
i remember reading somewhere that cephalopods concentrate unusual amounts of calcium in their flesh. is this true?

ive been trying to verify this for a while but the only piece of info ive come up with is that calamari has 15% of your daily value of calcium (whatever that means).
 

Tentacle Toast

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#2
Stands to reason; Ca is a critical element for neurological function, & between the changing of colors/textures of their skin, & arm/tentacle/sucker control alone I'd imagine the need for Ca is quite high, & could be why concentration is so high in calamary. Wether or not its localized in the extremities, I have no idea. In fact, I have no idea if that's why it's high to begin with, just a hypothesis;) could just be diet...good question! I'd love to see what the experts say...
 

DWhatley

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#4
The last I read, octos have no specific calcium need but that was based upon having no hard parts (like a shell, the beak is chitin like fingernails) and may not have taken into consideration other factors.
 

Tentacle Toast

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#5
I was basing my notion on the assumption that cephalopod's flesh must be HIGHLY innervated to undertake such functions. If this is the case, then elevated Ca levels could be due to more neural cells (thus more voltage dependent calcium channels) by mass. It'd be interesting to learn sodium content inrelation; despite living in salt water, these elements must be regulated within the tissue....I'd imagine, anyway. Marine biologist I am not...
 

Pr0teusUnbound

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#7
paper? no, not really. im just trying to confirm if cephalopod calcium content is unusual compared to other animals. if so, im wondering if it has something to do with why cephs never colonized freshwater habitats.
 

Tentacle Toast

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#8
I've wondered why no cephs exist in fresh water myself, living within minutes of both lakes Ontario & Erie. You're a fossil guy, do you know if there was ever a time when they inhabited fresh water? Please post back when you find anything out, I'd be interested in hearing...
 

Pr0teusUnbound

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#10
crap... it looks like cephalopods may not have unusually high calcium levels. :oops:

i just did some googling on the nutrition facts of calamari, squid, octopus, and cuttlefish and none of them have calcium levels consistently above 15% DV. the calcium levels are usually 1-8%
DV but mineral levels rise to 15-25% when fried or steamed. sorry for the false alarm.
 

Jean

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#13
Only calcified structures in cephs are statoliths (earbones if you like ~ 1mm long!!) Cuttle "bone" in cuttlefish, Stylets in some Octis and Nautilus shells!
 

DWhatley

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#15
Good to know that the calcium need appears to be non-existent as I had seen in the past but this is kind of question is always worth a look to improve our tank environments even though the question revolved around another topic. Always looking for clues on better longevity :biggrin2:

As an aside, it does appear that nauts need to be fed WITH shells but octopuses remove them and don't appear to eat anything but the meat (none of the cartilage from crabs seems to be eaten either). We have seen at least one octo consistently devain shrimp in addition to peeling it!
 

robyn

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#16
There is an important difference here between calcium carbonate, which is the calcium in shells and cuttlebones, and ionic calcium (calcium chloride most commonly when not free ionic) used in neurons and other cells. Even cephs with no calcified structures need calcium for cellular functions, like all animals.

About the speculation of high Ca2+ in tissue because of the 'rich' innervation - I have some doubts about this. Lots of other peripheries have very, very dense innervation (mammalian skin and body hair innervation, for example, is pretty darned extensive). Yes, cephalopods use their motor neuronal network to show off with chromatophores, and they do have a LOT of peripheral cell bodies in the arms, but I will bet you mammalian tissue rivals it.

Mammals absorb their calcium via their diets, and (presumably) cephalopods do too - I actually don't know for sure.. I guess they could absorb it directly from SW... But animals generally have no trouble getting enough of it from a regular dietary source without extra supplementation. In captivity, where food sources are far more homogenous than in the wild, supplemental calcium might be needed (just like it is in humans with bad diets...). For animals needing to make a shell in captivity (like Nautiluses), calcium supplementation might be necessary.

The original observation that calamari supplies a significant amount of daily calcium - I'm guessing this is common to many marine food sources.

About the marine-freshwater transition - it seems unlikely that calcium needs are a limiting factor. Many molluscs (with highly homologous physiologies and similarly substantially complex nervous systems) have colonised freshwater habitats just fine. I'd love to know why cephalopods never made it to freshwater, too. Any more thoughts on that topic?
 

Pr0teusUnbound

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#17
thanks for the detailed reply, but i wasnt really concerned with cephalopod dietary needs. my thinking was that if cephalopods had high concentrations of calcium in their tissues, it might mean that the had a hard time excreting excess ions like calcium. a weak renal system might be the the barrier that kept cephs out of freshwater.
 

robyn

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#19
Pr0teusUnbound;194801 said:
thanks for the detailed reply, but i wasnt really concerned with cephalopod dietary needs. my thinking was that if cephalopods had high concentrations of calcium in their tissues, it might mean that the had a hard time excreting excess ions like calcium. a weak renal system might be the the barrier that kept cephs out of freshwater.
Well I wasn't entirely sure what your primary interest was, so I gave a general reply to the major themes in the thread, not just your original post...

Have you read this thread? It contains some interesting discussion on the freshwater question, including several excellent walls-of-text from Monty.

Re-reading over his old posts always make me sad initially, but then very happy that his thoughts are still here with us!

http://www.tonmo.com/forums/showthread.php?10350-Freshwater-squid
 

Tentacle Toast

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#20
I think I could spend a solid month of 9-5 reading of this site, & still not be half-way through! I wish I would've been around here in Monty's time; he seemed to be quite a wealth of information. Definitely wove well into the tapestry. Those posts are well worth a look-see, pr0teusUnbound!
 

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