out of the blue

[monty]

OK, with all that being said, that is how you can have something you need also be toxic. As for where octopuses get their copper from, most of their food items (Clams, snails, crabs), also have copper based blood, and I would image provides them with ample copper for their own blood, in a safe form already bound to the hemocyanin.

I've heard that copper can also be toxic to other molluscs, though, so this just pushes back the question to "how do filter feeders and algae eaters like clams and snails get their copper?" I'd guess that they have some mechanism to extract it from the environment while avoiding toxicity, so presumably there is a "too little copper" as well as "too much copper" problem. As you say, though, it could also be the chemical form that the copper is in, somehow...

When hypothesizing about things like iron vs. copper levels in the environment, it's important to keep in mind that these blood pigments have been around for a very long time-- you can tell by looking at the differences in the proteins and genes that encode them in different species, and since we know from the fossil record that arthropods diverged from molluscs well before the cambrian, yet both have hemocyanin that shares enough characteristics that it couldn't have arisen separately, so hemocyanin evolved well before the Cambrian, which was a very, very long time ago. The atmosphere, oceans, temperature, other life forms, volcanism, and other geology of the earth were very different... so even if hemocyanin developed at a time when there was a lot of copper in the water for some reason, those conditions were at the time some early worm-creature first used it, say, to be able to out-compete other worms in some "eating bacterial mats or Ediacaran/Vendian critters" environment, or just to grow bigger in low-oxygen environment, so applying them to the modern creatures that use this pigment doesn't take the tremendous changes in the environment into account.

Perhaps a restatement of the question is "are there factors in having hemocyanin as a blood pigment that make it harder for those animals to compete in certain niches or environments?" or even "is there a pattern as to where hemocyanin-using animals get their copper, or do they show a number of diverse adaptations to get it?" and "how can we compare and contrast the similarities (convergent evolution) and differences (evolutionary diversity) that we see in the copper-using and iron-using animals, and learn anything interesting?"

This isn't to say that it's bad to ask the question of "how to the animals who live in a particular environment both take advantage of the resources and adapt to the constraints of the environment," I just think that because of the very long time-scale stability of the blood pigments that the particular pigment any animal uses is far more dependent on its ancestry than it's current environment. That can probably be decoupled, though, from the question of how the animals get the raw materials (e.g. copper, iron) to manufacture their blood pigments.

Here's an interesting twist to that: there are a lot of midwater squid that primarily feed on fish, right? Fish use hemoglobin, and probably don't have a lot of copper, and the squid have a very rapid growth rate, and so must add to their blood volume rapidly. They are cannibalistic to some extent, but there must be some other copper input to the system for the shoal of squid to ever grow in mass... perhaps that's part of the story where the Humboldts were filmed scooping up krill. Implications of this for researchers feeding their laboratory squids a diet consisting only of fish is left as an exercise for the reader.

 

[monty]

I am not quite sure what all animal have copper toxicity issues, but a lot of invertebrates do. I know most gastropods and bivalves have problems with copper, but I am not sure about crabs. I don't believe that the copper being toxic is directly related to copper being in their blood, so one can't assume copper in blood = copper toxic.

Yeah, I've spent a fair bit of time on google scholar trying to find references on what exactly it is about copper that causes problems for invertebrates, and what form that copper must be in to be problematic. I guess I haven't really gone the other way, and found out what form it's in in the medications that frequently cause problems in tanks.

I would expect in seawater that the majority is ionic copper, extrapolating from NaCl dissolving into Na+ and Cl- I would think cupric chloride would go to Cu2+ and 2Cl- or something like that, but wikipedia says that makes me really naive

 

[monty]

p.s. a little further reading suggests that the Ich treatments are copper sulphate. The wikipedia page Copper sulfate - Wikipedia suggests that copper ions that result from that are toxic to fish, so care is needed not to overtreat. This is also an interesting reference on treating Ich: http://edis.ifas.ufl.edu/FA006

 

[DWhatley]

To extend our naivety, would it be viable to suggest that the need for copper to increase blood volume be a partial reason cephs need a higher salt content than most other reef critters?

 

[monty]

To extend our naivety, would it be viable to suggest that the need for copper to increase blood volume be a partial reason cephs need a higher salt content than most other reef critters?

Er, I'm not really clear what you mean... table salt is NaCl, so no copper is in it.

Apparently, "Standard Seawater" (per http://www.geochemie.uni-bremen.de/koelling/standards_seawater.html ) has a bit of copper, but the "Artificial Seawater" variant described on wikipedia at Artificial seawater - Wikipedia has none. See also at Seawater - Wikipedia

They certainly can't make copper from salt water alone (NaCl in H2O) without nuclear fusion. Not that I have anything against cephalopods with nuclear fusion capabilities.

Certainly, since there are land-based and freshwater critters with hemocyanin, being in salt water isn't a general requirement... in fact, freshwater and land molluscs don't enjoy salt much at all...

 

[DWhatley]

I had forgotten that copper is one of the things intentionally excluded from the artificial sea water salt mixes. To be honest I grasp at a lot of straws to try to explain why my tank reared mercs were half the size of the WC mom and the tank bred were half the size of the tank reared (Wiley, my last of Trapper's line is tiny and getting to be an old man). Quantity of food available does not explain it and I am kind of alone in the hobby world with this experience. I keep hoping others will continue a line of cuttle or octo to see if this is typical of something I am not providing.

 

[OB]

Not that I have anything against cephalopods with nuclear fusion capabilities.

I, for one, welcome our squid overlords

 

[octokidwriter]

dear friends

as this discussion continues, i feel the urge to write a horror novel with mad nuclear octopus scientists ready to destroy the world for want of a bite of good copper, should make a best-seller, especially if i include these hair-raising conversations...

 

[cthulhu77]

I, for one, welcome our squid overlords

We are here. Bow down.

 

[OB]

Don't mock me, I've seen what even their most docile blobs can throw at us, this is no time for dilettant humour! Next thing you'll know you'll be humming along to Sweet Caroline...

 

[octokidwriter]

i have a completely new question: i have been surfing around for information for weeks now and i seem to find contradictory information about the difference between squid and octopus: squids have inner shell, octopuses don't, squids have two extra tentacles, but some say the only difference is in the suckers, squids have hooks on them ??? when i look at photo's it seems indeed difficult to see the difference between some octopuses and some squids. how could one explain this Very Simply?

 

[cthulhu77]

Octopus have 8 tentacles (arms), while squid have ten. With a squid, two of those are used as grasping arms for catching fast moving prey, and many species have sucker disks with hooks.

If you see video of a squid hunting versus an octo, you will understand quickly. Octopus typically hunt by ambush, sneaking up on the prey item, whereas squid chase down their food by using pure speed.

Many of the cephalopods have a "cuttlebone" that varies in size from species to species. In some, it is as thin as a piece of packaging plastic, and in others it is thick enough to warrant saving for parrot chews. Sigh.

 

[Taollan]

Sorry before-hand for the horrible formatting:

"An interesting element in cephalopods is Cu. Thismetal
is required in large concentrations in cephalopods as it
works as a respiratory pigment in hemocyanin which
represents 98% of their blood proteins (Ghiretti, 1966;
D'Aniello et al., 1986). From the literature, levels of Cu are
reported for the gills, branchial hearts, digestive gland and
muscle of adult cephalopods, including O. vulgaris (for
recent literature review see Table 6 of Napoleao et al.,
2005a). The Cu concentrations observed here in O.
vulgaris hatchlings are similar to that reported for the
gills of adults of the same species. The Cu abundance in the
adult octopus gills may reflect the presence of haemocyanin,
the dioxygen carrier Cu protein typical ofmolluscs and
crustaceans (Taylor and Anstiss, 1999). However, these
levels of Cu for the octopus hatchling, as a whole animal,
seem to be relatively high compared to the adults. The
richness in Cu of planktonic octopus may indicate a
particular high nutritional requirement for this element. In
decapod crustaceans, enzymatic requirements have been
estimated to be around 26 μg g−1 of Cu and the total
metabolic requirements (enzymes and haemocyanin) to be
around 83 μg g−1 (Rainbow, 1988; Zauke and Petri, 1993).
These estimated requirements for adult octopus are similar,
reaching levels of 26 and 92 μg g−1 of Cu, respectively
(White and Rainbow, 1985). Crustaceans constitute the
main prey of many cephalopod species, particularly during
paralarval and juvenile stages (Vecchione, 1991; Passarella
and Hopkins, 1991) and crabs are the preferred prey of
adult octopus in the wild (Nixon, 1987), between other
reasons, probably because they are rich in Cu, Zn,
cholesterol and n-3 fatty acids (King et al., 1990; Skonberg
and Perkins, 2002). García García and Cerezo Valverde
(2006) reported the optimal proportion of crabs in a fish
+crab diet for ongrowing subadult O. vulgaris, noted that
no cannibalism are reported when the minimum levels of
crabs are maintained in the diet and pointed out a possible
Cu dietary influence. In the same way, mortality associated
with low Cu content diets has been also signalled for
subadult cuttlefish S. officinalis (Castro et al., 1993).
The present results seems to confirm the importance of
the Cu in the diet of O. vulgaris as 1) paralarvae of 20 d
old feed on an Artemia diet showed significantly less Cu
content that the “natural” Cu profile of hatchlings or wild
juveniles, and 2) the paralarval group with poor survival
(control) recorded the lower Cu content in comparison
with the higher levels recorded for the group with best
survival. In addition, prey composition analyzed here
showed that Artemia nauplii have Cu levels 20 times
lower that O. vulgaris hatchlings and 8 times lower that
M. brachydactyla zoeae, a prey used previously with
success as food for rearing O. vulgaris paralarvae
(Carrasco et al., 2003; Iglesias et al., 2004). The low levels in Cu of the reared O. vulgaris paralarvae feeding
on Artemia nauplii may suggest that they are resulting
from the low Cu content of Artemia and/or resulting from
the poor physiological stage of the octopus paralarvae.
Conclusions on this subject need further research,
however, the Cu content of the M. brachydactyla zoeae
(73 μg g−1, see Table 5) may be considered as an optimal
estimation of the Cu feeding requirement for O. vulgaris
paralarvae under culture conditions. The deficient nutrient
composition of Artemia as the sole larval food for O.
vulgaris paralarvae is well known, particularly for lipid
requirements (Navarro and Villanueva, 2000, 2003;
Villanueva et al., 2002). However, in addition to other
nutritional requirements, mainly from lipidic origin, Cu
seems to be an important element on the paralarval octopus
diet. Future studies are necessary to quantify these
Cu dietary needsmay testing a possible lipid+bioavailable
Cu enriched Artemia suitable for paralarval octopus culture.
To this respect, it should be borne in mind that Cu
uptake by Artemia is influenced by pH and temperature
(Blust et al., 1988, 1994)."
From:
Villanueva, R. and Bustamante, B (2006) Composition in essential and non-essential elements of early stages of cephalopods and dietary effects on the elemental profiles of Octopus vulgaris paralarvae. Aquaculture 261:225-240

 

[octokidwriter]

A popular misconception is that squid have eight arms and two long tentacles, while octopus have eight arms and no tentacles. But this is not always the case. The only real difference between the two groups is that squid have hooked or saw-like suckers, and octopus do not

http://www.teara.govt.nz/EarthSeaAndSky/SeaLife/OctopusAndSquid/1/en

 

[Taollan]

http://www.teara.govt.nz/EarthSeaAndSky/SeaLife/OctopusAndSquid/1/en

I am going to have to respectfully disagree with the website you quoted. The presences of two tentacle in addition to eight arms is the fundamental difference between octopuses and squid. Yes Some squid seem to only have eight arms (Family octopoteuthidae) But even in those squid I believe you can detect extremely reduced tentacles or you can tell they lose them during development

I can't think of a particular squid that lacks sucker hooks and sucker rings, but lets consider this:
if a cephalopod was discovered today that has no sucker hooks or rings, but did have eight arms and two tentacles, the information from the above link would suggest that such an animal would be considered and octopus. I would contend it would be instead a squid (or cuttlefish or other decapodaform).