out of the blue

Your question makes perfect sense... here is my stab at answering it:

Octopuses are one of many organisms that use copper-based blood (the molecule containing the copper is called Hemocyanin, analogous to hemoglobin in humans and other vertebrates, which contains iron). Essentially all other mollusks have copper-based blood as well (with a few odd-balls using iron-based blood, mostly hydrothermal vent critters), as well as arthropods (insects, spiders, crustaceans like crabs and lobsters) and some various worms. Really there are probably more species on earth today that have copper-based blood than iron-based.

Why octopuses use hemocyanin (copper-based blood) rather than iron-based blood is a really big question that is very hard to answer simply. The best reason is probably because their ancestors did (other mollusks). But using copper based blood gives them a couple of advantages, one of which being that it can work better when the octopus is in low oxygen environments.

Why is there blood blue? Well that is because copper is blue in the particular oxidation state (fancy phrase meaning how it is bonded to other things) of which octopus blood uses it to carry oxygen. Metals turn different colors depending on how they are bonded to other chemicals, like oxygen. Fort instance pennies appear the familiar "copper" color, because they are bound to a lot of other copper molecules. The Statue of Liberty, however, looks green, because the copper it is made of has "rusted" and bound to oxygen. The copper in octopus blood is bound to both a blood molecule (the hemocyanin) and an oxygen molecule, so it turns blue. You can see the same thing in your blood, with the iron in it. When the iron in your blood is bound to both oxygen and hemoglobin, it is red, but when the iron is not bound to the oxygen anymore (in your veins) it is blue. You may be interested to know that octopus blood when there is no oxygen in it (so when it is in the veins instead of arteries) is actually clear, and not blue.

As for octopuses getting tired out more easily because of using copper-based blood, this is really blown out of proportion by most people. This is very true for a lot of other organisms that use copper blood (like crabs and such...) but octopuses and squid are such high performance animals (especially for invertebrates), that they have overcome more other the limitations of copper-based blood, and really it has performance comparable to some fishes.

Ok, that is a very long response to all of that... if there is anything you don't understand, let me know and I explain it another way, or if you want to know anything else... just holler.
 
Taollan said a lot there (:notworth:) but I'd add a couple of other details, just 'cuz:

I doubt there's much more copper at the bottom of the ocean than iron. Something I've always found a bit peculiar is that octopuses, and many other invertebrates with copper-based blood, find very small concentrations of copper toxic. So it's an element that's vital for their survival, but they can't stand it. Of course, nitric oxide and chlorine are similar for humans: they're important for us to live but toxic when we breathe them.

In both hemocyanin (sometimes spelled haemocyanin, for extra confusion) as in hemoglobin (haemoglobin) most of the molecule is a big structure made of the usual protein components, and there is just a big metal ion smack in the middle, that is very good at binding to oxygen-- in a probably-oversimplified example, a bar of iron will oxidize into rust, just as a bar of copper will oxidize into "verdigris." (confession: I don't know how much the fact that pure metals are easily oxidized is related to is use binding oxygen in blood... one difference is that in blood, the process is easily reversible, while you can't really "un-rust" metal easily.)

Understanding "why copper" may often be a historical coincidence, too: some early organisms developed hemocyanin as an oxygen transporter, which gave it a huge advantage over something that didn't have it, and others developed hemoglobin, which also gave an advantage over just using oxygen dissolved in seawater or similar. Both types of animals could be more active, and larger, but there's no easy path for an animal of one ancestry to lose one of these transporters and gain the other (although, to be fair, a few molluscs have done that, apparently... I wonder if anyone knows the mechanism... transgenic / horizontal gene transfer? retrovirus? mutation?)

Evolutionary genetics has a notion of "strongly conserved" characteristics, and in this case, the ability to efficiently transport oxygen is so vital to the survival of these animals that most changes away from their favored blood "pigment" are very much selected against, even if there is a "better" pigment that would work for... Evolution is usually about adaptation to "nearby" characteristics, and while the more radical changes make a bigger impression, they're not really the bulk of changes, and happen much more often in mass extinctions followed by species radiations. In the case of blood pigments, one might hypothesize that in a low-oxygen period, any animal that didn't have really good oxygen transport died out, and perhaps hemocyanin and hemoglobin were the only "good enough" systems for active animals, and after the oxygen came back, those two groups "radiated" with relatively small changes to take over all of the niches left when animals that used other pigments died out. Sometimes, the importance of a something in ancient history gets "locked in" as well: because the blood pigment was so important millions of years ago, now animals have very efficient systems and can be very wasteful of oxygen, by being active, smart, fast predators like cats, or fast and active fliers like hummingbirds, or cerebral big-brained primates like us. But in the current world, any species that doesn't have a good oxygen transport system is at a severe disadvantage compared to the ones who ran the gauntlet millions of years back, so any changes that move away from the "good" system are liable to make things worse before they make things better.
 
Is there another know oxygen carrier today besides hemocyanin and hemoglobin? If so what creatures use it?

Why keep a octopus? I can't give you an answer but I will throw out some ideas that might weave their way into your imagination.

From my observations of people looking at my various marine tanks, there are some people that have an immediate negative reaction the first time they see an octopus. You can almost see shivers and the reaction is much like people that are terrified of spiders or snakes (people terrified of spiders do not necessarily translate that to octos though, even with the eight arm similarity) . Then there are people like those who dwell here and the first reaction is total facination. I am not sure what makes the reaction so opposite. I can suggest that is it not familiarity with the ocean, however, as the diver/collector that caught my favorite pet was very much afraid of him and another diver/collector I know cannot understand why anyone would want to keep one. Fishermen consider them a nuisance and/or bait. The wife of the first (not a diver), however, was infatuated when Lynn caught and brought Octane home. My 9 year old granddaughter enjoys watching and feeding them and finally decided she wanted to pet mine, her teachers don't believe her, even with pictures (however, this was true of seahorses as well and they don't tend to have the negative reaction observed with the octo). Some people will describe them as "slimy" other as "soft" I would use "cuddly" but I don't think many others would agree to that adjective - but then again, we are seeing more and more stuffed animals and baby toys depicting friendly octos. Perhaps it has something to do with a Doctor Do Little syndrome and a wish by some people to have the ability to communicate with animals while others find the idea absurd.
 
dwhatley;123626 said:
Is there another know oxygen carrier today besides hemocyanin and hemoglobin? If so what creatures use it?

I don't know if this counts, but some animals don't have special carrier molecules, and use seawater, and I think some use other fluids (including sap, in plants, perhaps) or just diffusion of oxygen through tissues.

I'm pretty sure starfish and other echinoderms just use seawater to get oxygen around. Sponges even more so... I think starfish do some active pumping, while sponges use little cillia (moving hairs) to move fresh, oxygenated water around.

I don't know if there are any animals with closed circulatory systems that use dissolved oxygen but don't have a carrier molecule that's hemoglobin or hemocyanin, but I think some don't have special cells like our red blood cells, and even if there aren't any now, it seems likely that animals developed a closed circulatory system first (probably in the Cambrian or earlier) in order to become larger and bring oxygen to the parts far from the outside, and then carriers were an improvement on that model. Worms frequently survive as the last of such animals, so I wouldn't be shocked to find some surviving worm that still works that way.

I looked up velvet worms, since they're often interestingly weird, and found that

Internally, velvet worms have a tube-shaped heart that pumps blood through an open circulatory system. The blood, however, does not carry oxygen. Instead, oxygen is brought in through minute trachea located all over the surface of the skin. The openings to these trachea are sites of major water loss, but similarly can easily cause the drowning of a velvet worm. Thus, the phylum Onychophora is the only phylum in which none of its living members are aquatic.
(from Velvet Worms - Phylum Onychophora )

This is, in fact, nice and weird, particularly since their ancestor Hallucigenia was aquatic so presumably didn't have the drowning problem. Exactly what the blood is used for if it isn't respiration isn't clear, perhaps just for getting nutrients to the cells and waste (maybe including CO2) away from them? But it doesn't answer your question :rolleyes:
 
this is all amazingly mindbogglingly interesting though it might take me some time to digest all...so i'll just quietly chew on this all day (all night for most of you on the forum :smile:

thanks!

anna
 
dwhatley;123626 said:
Is there another know oxygen carrier today besides hemocyanin and hemoglobin? If so what creatures use it?

Hemerythin: it is another iron containing O2 transporter but lack a Heme group that defines Hemoglobin and Hemocyanin. Sipunculids and Brachiopods use this transporter

Vanabins: These are metalloproteins that bind vanadium (strange, strange:bonk::cyclops:) and are used as blood O2 transporters by Tunicates.

I can't think of any others right off, but I will let you know if I come up with some.
 
Taollan;123644 said:
Hemerythin: it is another iron containing O2 transporter but lack a Heme group that defines Hemoglobin and Hemocyanin. Sipunculids and Brachiopods use this transporter

Vanabins: These are metalloproteins that bind vanadium (strange, strange:bonk::cyclops:) and are used as blood O2 transporters by Tunicates.

I can't think of any others right off, but I will let you know if I come up with some.

Ah, delightfully good esoteric information :notworth: :grad:

Is there a good reference for "comparative oxygen transport systems" across the Animal kingdom, or is this the sort of stuff you have to pick up on the street? I utterly failed to find the right google terms to find such a thing, and while there are some good refs in books I have about lung/gill anatomy and such for oxygen uptake, I found almost nothing about how it gets moved around after it's in the body.
 
a down to earth question arises in my simple mind...i somehow thought that the elements in the blood of living creatures is due to what they take in as food, so a copperblooded creature would need to take in some copper to stay healthy, whereas we ironblooded ones need some iron to survive (like when you've donated blood, sometimes you're given iron pills to strenghten yourself) so it would be logical that creatures are either hemoglobinous or hemocyaninous depending on what element is most available in their surroundings

sincerely hoping this question will not be provoking roars of disdainful laughter, i remain, etc

your interested pupil :snorkel:
 
'fraid not, even small traces of copper are deadly to an octopus and is the first mentioned problem with purchasing a used siliconed sealed tank that may have been treated with a copper medication.
 
Back in 2000, Heinz Decker and Nora Terwilliger published a good paper on the evolution of copperbased oxygen carrier molecules:

COPS AND ROBBERS: PUTATIVE EVOLUTION OF COPPER OXYGEN-BINDING PROTEINS
The Journal of Experimental Biology 203, 1777–1782 (2000)

©The Company of Biologists Limited 2000

The grounds for it being utilized by cephalopods in preference to iron, is likely that it works well based on its physical properties in an oxygen scavenger molecule, and certainly well enough to survive the competition and get awarded evolutionary success as a carrier in a circulatory system. Again, as the case was made earlier in this thread by Monty, once you (as a lineage) invest energy in a certain route of evolution for one of your basic requirements, it is nigh to impossible to reverse and go an alternative route altogether; think composite eyes, for instance, or arthropod trachea versus a proper respiratory system.
 
:confused:

be patient with me, all of you, if i keep on asking what seems the same question over and over again:

this copper-in-blood-issue: discussing this over dinner just now (yes, well, obsessed writers tend to involve their whole family) with my husband, he kept on wondering where the copper in the blood then did come from, if not from food and why it was so poisonous, and yes, common reason says it doesn't make sense that you die from what you need to survive. do other "copper-in-blood animals" have this huge allergy to copper as well?
 
An element in one form can have totally different physiological effects than in another form. Lets use a human example: Chlorine. You absolutely need chlorine to survive. If we were somehow able to take every last chlorine molecule out of your body, you would die instantly. You normally get chlorine in the form of sale (NaCl, sodium chloride). When salt is dissolved into solution in water, the chlorine molecule separates from the sodium molecule and is just the negatively charge ion, Cl-. This ion is what your body will take up and use.
If the chlorine is in the "elemental" form, bound to another chlorine (Cl2) it is usually a gas and is very toxic to humans.
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.
 
thanks, very clear now!!! will explain to my kids at bedtime :hmm:
it is just that it seems not such a good idea for an octopus to be so queezy about just a little copper, something which i can imagine is easily found anywhere

do the other copperbound animals (spiders, crabs, etc if i'm not mistaken) have this problem as well?
 
monty;123676 said:
Is there a good reference for "comparative oxygen transport systems" across the Animal kingdom, or is this the sort of stuff you have to pick up on the street?

I don't know of one right off. I was slow in answering because I was poking around. I mean there is a lot of stuff out there looking at Hemoglobin and hemocyanin comparisons, sometimes even grabbing Hemerythins, but I don't know of anything right off that is global. My best reference for some of these is "Invertebrates" by Brusca, which was my Ad. Marine Inverts class text in my master's program. I think it has everything I mentioned in it. (Verts are boring... I think they all only use hemoglobin)

P.S. I have one more for you, that I shouldn't have forgotten. Chlorocruorin, which is another iron-porphyrin ring repiratory pigment used by some annelids.
 
octokidwriter;123832 said:
do the other copperbound animals (spiders, crabs, etc if i'm not mistaken) have this problem as well?

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.
 

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