Do All Animals On Earth Have Iron Based Blood

Dear Cecil:

The horseshoe crab is 1 of the oldest species on earth, yet it is 1 of the few (if not the only) species with copper-based blue blood. The rest of us recently adult beings have red, iron-based claret. Did all creature life on earth at one time take copper-based blood? Did natural pick favor ruddy-blooded beings? Or would all earth life yet have blue blood if it hadn't been for an invasion of iron-blooded beings from the red planet, Mars?

J. Watson, Omaha

Cecil replies:

All correct, today'southward blood twenty-four hour period; cookies and juice at the end of the column.

1 of the chief functions of blood as information technology's evolved over the eons has been to ship oxygen around an organism's body. Early oxygen-breathing life forms were express in their complexity in part because their primitive circulatory fluid just wasn't very practiced at this task. But things really perked upwardly life-on-earth-wise in one case creatures started producing blood pigments — metal-containing compounds that are able to catch onto oxygen molecules and release them when and where needed. In ruddy-blooded animals the critical paint is hemoglobin, the primary constituent of blood-red claret cells. Hemoglobin molecules are structured around atoms of iron, and it's these that give the blood of vertebrates its vivid cherry-red color. (Well, brilliant scarlet when information technology's laden with oxygen, duller red when it'south on its way dorsum to the lungs.)

Hemoglobin's skillful at what it does, but every bit you note it's not the only game in town. The horseshoe crab indeed relies on hemocyanin, a copper-based pigment that makes blood blueish. Yous're right, too, that horseshoe crabs are some of the more ancient animals yet in business — they've been scuttling around for something like 540 million years — just they're far from the only extant species to have gone the copper route. After hemoglobin, hemocyanin is the second most ordinarily encountered blood pigment, and plenty of other arthropods (including lobsters, crabs of the nonhorseshoe variety, and contrasted insects) and mollusks (amid them snails and octopuses) have blue, copper-based blood. There are other pigments out there every bit well, and some animals apply more than one oxygen carrier; scientists aren't certain, but the invertebrates known as sea squirts may do their breathing via a combo of hemocyanin and vanadium-based compounds.

Neither hemoglobin nor hemocyanin seems to have evolved from the other — show suggests each originated independently a billion-plus years back. (There's speculation that both pigments may accept initially developed in organisms to which oxygen was toxic, and that their original function was to neutralize O2, not ferry it around.) Generally speaking, hemocyanin isn't equally efficient at carrying oxygen as hemoglobin, but you can pack more of it into the same infinite. It seems to work well for aquatic creatures in oxygen-rich habitats, and information technology may provide some advantage where the water is common cold and relatively acidic.

Horseshoe crab blood is extremely useful stuff, it turns out, and not just to the venereal. One danger in the manufacture of pharmaceuticals is a peculiarly rugged grouping of bacterial contaminants chosen endotoxins. So say you're mixing up a batch of meds — how exercise you determine whether it's endotoxin free? Add some horseshoe crab blood. A substance in information technology called Limulus amebocyte lysate, or LAL, volition rapidly bind to any endotoxin present and clot, telling you lot you've got bad medicine. Harvesting LAL is a $l one thousand thousand-a-year industry; a quart of crab blood will prepare you dorsum about 15 grand.

Dear Cecil:

Me and a friend got into a conversation near moving to a different atmospheric condition climate. She told me that blood thickens or dilutes every seven years, so after seven years y'all get used to any conditions. To me that does non seem exactly right, merely I was curious if there is any truth to this.

— Bearding, Saint Louis

Cecil replies:

You read a question like this and your offset reaction is: I am now looking at one of the dumbest things e'er committed to writing. Just as yous're set to motion on, though, yous can't help thinking: OK, merely mightn't there be a mangled nub of something in in that location worth addressing? And after some reflection you realize: Really, at that place is.

Blood isn't similar motor oil — it doesn't just thicken up when the weather condition gets brisk. Yes, low temperatures touch on blood viscosity, and exposure to astringent cold might upshot in temporary claret thickening in the extremities. But it would take a very serious drop in body temperature to cause any pregnant thickening of 1'southward blood overall.

No, what nigh determines the viscosity of blood is the proportion of red claret cells in it, which is chosen hematocrit. An xi percent increase in hematocrit volition raise blood viscosity near twenty percent. And here we arrive at the mangled nub. At loftier altitudes, your torso adds red blood cells to the mix to pull more oxygen out of the thin air. And then if y'all motility from LA to La Paz, your blood will in fact thicken to help yous acclimate.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.

Source: https://www.straightdope.com/21343877/crabs-have-blue-blood-why-don-t-we-plus-does-your-blood-thicken-in-a-cold-climate

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