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I need a creature that can survive in environments with elements like lead and mercury in many nutrition sources, and in some places making up part of the atmosphere.

I was thinking maybe it could have an organ with other elements that readily bind with the heavy metals, making them not toxic or detrimental. However, I'm not well versed enough in chemistry or biology to know if that makes sense.

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3 Answers 3

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Creatures that evolved in metal-rich environments would be immune

Evolution could take care of the toxicity problems. Metal toxicity is a characteristic of many different metals, and the root cause for why a metal is poisonous varies widely between metals. For example with arsenic:

Arsenic interferes with cellular longevity by allosteric inhibition of an essential metabolic enzyme pyruvate dehydrogenase (PDH) complex, which catalyzes the oxidation of pyruvate to acetyl-CoA by NAD+. With the enzyme inhibited, the energy system of the cell is disrupted resulting in cellular apoptosis. Biochemically, arsenic prevents use of thiamine resulting in a clinical picture resembling thiamine deficiency.

Arsenic interacts with specific enzymes in a specific way to disrupt them from doing their biological job. The solution is for organisms to evolve specific methods for resolving whatever biochemical problem the metal causes. For arsenic, an animal which evolved so that that allosteric sites on the PDH complex enzyme are not receptive to arsenic. The biochemical reaction chain is broken, and now arsenic is not any more problematic to us than eating iron (well...there may be other problems arsenic causes, this is just the one that kills you fastest).

Humans are immune to the metals common in the environment

In the Earth's biosystems, certain metals are present in certain quantities. These metals are needed for nutrition, iron, magnesium, potassium, etc. The amount of iron or aluminum, two common metals, found in organic matter will not poison an organism on Earth, since all organisms on Earth have had to deal with these common metals for billions of years.

If you planet has a different geo-chemistry, or different elemental abundances in the crust, the creatures of your planet, since the inception of life, will evolve a resistance to the metals commonly encountered. Therefore, you can assume that any creature on a heavy-metal-heavy planet would be immune to the commonly encountered heavy metals.

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    $\begingroup$ I broadly like this answer, although I'd suggest that immunity is not required. Life tends to work fine as long as it has enough time to reproduce (and in more complex lifeforms to raise the "kiddies" :-) ). That doesn't require immunity just reasonable tolerance for some period of time. $\endgroup$
    – StephenG - Help Ukraine
    Nov 21, 2018 at 19:09
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    $\begingroup$ Some metal may actually get incorporated, there are bacteria that evolved in arsenic rich areas that actually use it in enzymes. $\endgroup$
    – John
    Nov 21, 2018 at 19:15
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    $\begingroup$ For an example, here's a microorganism that's adapted to high concentrations of arsenic: en.wikipedia.org/wiki/GFAJ-1 More generally, if you search for "bioremediation heavy metal" you'll find lots of links to microorganisms that tolerate various metals. $\endgroup$
    – jamesqf
    Nov 21, 2018 at 19:43
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    $\begingroup$ @StephanG - not really. life tends to work fine as long as it isn't poisoned. poisoning usually takes place precisely along these lines - knocking out enzymes, or attacking structure. the only thing reproduction provides is trials for a suitable mutation to do precisely that - alter the enzyme, protect the structure. $\endgroup$
    – theRiley
    Nov 21, 2018 at 19:46
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    $\begingroup$ @Aethenosity I don't know if it is reasonable to have all heavy metals abundant on a planets surface. There are a lot of heavy metals, and some are much more common than others. My first instinct would be to say that any process that makes iridium or rhodium a common metal would also mean the planet would be made almost entirely of tungsten, barium, and lead. Perhaps that is the basis for another question? $\endgroup$
    – kingledion
    Nov 22, 2018 at 2:44
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The creature’s small intestine has a magnetic lining that attracts heavy metals. It removes metals when the food is liquefied, for easy separation. The magnetic field can be created by magnetizing small chunks of iron using electric currents in nerve fibers.

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I would start with the igaunas of Galapagos as a reasonable visual of what some creature plaqued by pesky heavy metals could look like. Constantly excreting the poison through the nose and skin.

Of course some metals in microscopic doses are necessary and tolerable. So yes the organ might work which picks up and filters the blood. But really the metal would mostly enter through skin and lungs. So those organs must feature some coating or ingenious enzyme that eats the metal, sends it to another special organ which turns it into energy or poison the animal could use as a defense. Also you could use a magnetic aura against the non-ferrous metal or an acid which dissolves it. And maybe that special organ could have a separate chamber which pools the ferrous metals and excretes them to be harvested by humans or other symbiotic creatures.

This feature of metal eating creatures might give them some supernatural abilities. Might even allow them to talk to each other telekinetically, or Have metal skin, poisonous concentrations of saliva, or a lot of other scientific uses.

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    $\begingroup$ note: metals can't be eaten/digested. they are elements. they can be 'handled' by chelation & excretion, though, as you allude to.en.wikipedia.org/wiki/Chelation $\endgroup$
    – theRiley
    Nov 21, 2018 at 20:43
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    $\begingroup$ just be be clear, metals are used as cofactors in enzymes, the alkali metal ions have a variety of uses, but no metal is consumed or digested. the cofactors' capacity for orbital geometry changes associated w/ oxidation state changes are used to modulate protein activity. but the metals are not, in any way, deconstructed. that's all i'm trying to get across. $\endgroup$
    – theRiley
    Nov 21, 2018 at 20:51
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    $\begingroup$ you can't digest an element. i'm sorry. digestion implies decomposition.digest 1. break down (food) in the alimentary canal into substances that can be absorbed and used by the body. its the breaking down part that doesn't apply, not the absorb & use part. carry on! $\endgroup$
    – theRiley
    Nov 21, 2018 at 21:32
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    $\begingroup$ all metals are elements. i'm not trying to be difficult. this is a fact-based place, and all i'm trying to get across is that metals aren't digested. if this point is coming across that way, I apologize. $\endgroup$
    – theRiley
    Nov 21, 2018 at 21:53
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    $\begingroup$ i believe you are conflating redox reactions, which have equilibria, are reversible, etc.with catabolism. at any rate, there is no mention of digestion in the wiki entry you linked. all cells derive energy from the electron transfer mediated by the metal H in the protonation/deprotonation NAD+/NADH shuttle. i do see your point, in the sense that iron is being harvested from the external environment directly for energy, similarly to the energy product of digestion (as in, breakdown/energy extraction of biomolecules). perhaps you should write to the dictionary people. :) $\endgroup$
    – theRiley
    Nov 25, 2018 at 6:42

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