This is something I’m struggling to find answers for online. I need to be able to explain and justify the biology of a species that capable of surving in multiple environments including changes in temperature, pressure and atmospheric content and perhaps even radiation levels.

It goes much further but the short version is that these creatures are insanely tough and versatile. The problem is that a ‘jack-of-all-trades’ species isn’t very believable and most environments often require very specialised life.

One option I consider is parasites but struggle to find information on helpful parasites and what they excrete. I know a little about the Excretory systems and the Lymphatic system but what I want to know are the physical limits and whether ‘positive’ parasites could or already do bolster these or even result in entire systems evolving over time within the body.

I’m piecing together a complex jigsaw but my first question is whether any of you know of any simbiotic relationships where parasites in a creatures bloodstream, lungs or dermis are directly responsible for coping with oscillations in environmental extremes and excreting or repurposing inhaled or absorbed material from the threatening environment?

(In my head I’m imaging things like bacteria in the bloodstream changing nitrogen gas to nitrogen solid or perhaps some system that takes dust particles from the lungs, combines it with keratin and builds a toughened layer of something on the skin using the aquired materials)

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    $\begingroup$ As a first off note, parasites always have disadvantageous effects for the host. I think what you would be looking for is either a mutualistic or commensalistic relationship. Mutualistic relationships both benefit from, such as your gut bacteria, while commensalistic only one benefits. $\endgroup$
    – Umbra
    Dec 9, 2019 at 16:18

3 Answers 3


First of all,

biology of a species that capable of surving in multiple environments including changes in temperature, pressure and atmospheric content and perhaps even radiation levels.

you're in luck because we already have that species here on Earth. Tardigrades are extremely tough animals that are known to have survived, among other things, the outer space - without air, and subject to direct radiation from the sun.

In your post you don't mention how 'advanced' you need your species to be. If they don't need to be a large land dwelling mammal equivalent, then you already have your answer. You don't need to explain anything.

If you need them to be a large land dwelling animal, then it is possible that it can bring in complications. All traits of animals are a result of evolution. And almost all traits are 'energy expensive', and often evolution tends to take the easiest path. Commercial strawberries, blueberries, etc are extremely rich in sugar, because of centuries of human cultivation. But wild berries have a much smaller sugar content, because sugar is expensive to produce, so it's only as sugary as it needs to be in order to attract pollinators in the wild. And those pollinators aren't as choosy as us humans, so they can afford to be less sugary.

The same principals apply here. You need to set up conditions which gives a species an edge over others when surviving such environments. Maybe your planet has a very volatile weather pattern where temperatures can wary from -20C to 50C (or even more) within days or even hours. Maybe that planet's sun is much more powerful than ours, and the radiations levels even at the sea level is much higher. You get the drift; set up the conditions in which being able to survive harsh conditions is a big evolutionary advantage.

The second part of your question, parasites, are an extremely complicated subject which even modern biologists have a minimal understanding compared to a lot of other fields.


simbiotic relationships where parasites in a creatures bloodstream, lungs or dermis are directly responsible for coping with oscillations in environmental extremes and excreting or repurposing inhaled or absorbed material from the threatening environment?

again, we kind of have that in our world. Scientists suspect (not proven, but there's very strong evidence to support this hypothesis) that Mitochondria were once an independent life form, which at some point in our deep evolutionary history 'infected' Eukaryotas and started permanently living inside them, and turned out to be a symbiotic relationship, and now we can't survive without them, and they without us. You could argue that your second case too is not a far fetched one, but one that already exists.

How much detail do you want to go into? If you're writing a story you don't necessarily want to explain every single details of it, if you can base things in solid science, which in this case seems like you can, then that should be good enough?


I can recommend a few books about parasites for you if you would like to dig deeper. These are extremely entertaining books in their own right and can get you hooked even if you didn't need them for your research.

  • $\begingroup$ Thank you for your answer Sach. We are discussing a large land based creature but by introducing successful and versatile micro organisms I can perhaps theorise on how absorbing that life could one day develop into a useful system. I’m glad you mentioned Mitochondria because that was an example bouncing around in my head of where that sort of thing has happened. $\endgroup$ Dec 9, 2019 at 19:40
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    $\begingroup$ You will need to think about time and complexity, though. Mitochondria taking up residence inside us happened (if it did), really early in our evolution, when we were much simpler creatures. So they had time to adjust, and neither were nearly as complex as a large land based creature. So the parameters are different; evolving together early on is much easier than making your creatures evolve a co-dependence after one of them is already a complex creature. $\endgroup$
    – Sach
    Dec 9, 2019 at 19:44
  • $\begingroup$ I want this species to take a very specific route physically, culturally and technologically. I’ve found that in order for that to happen I need to plan their route from day one, going as far back through the evolutionary timescale as possible, even unto Clay Catalized Organic Reactions. My interest in oscillating environments comes from the fact that complex life (complex as in cells) began to appear very early on when the planet was still roasting hot, geologically active and I have lot of theories on how life could still find a way. $\endgroup$ Dec 9, 2019 at 19:44
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    $\begingroup$ I’m a great believer in what writers call ‘The Invisble Book’, for every story they write they have mountains of research and backstory that the final draft never includes but is still so important. And if watching YouTube teaches us anything it’s that fans have thousands of questions and theories and will talk about if for hours. I’d love to have accurate, pre-planned answers to their questions. I’d like the story to be believable. $\endgroup$ Dec 9, 2019 at 19:47

I think there's a limit to how much mutualism would able to help, unless the environmental change happened very slowly.

More likely, your "useful parasites" are biological nanites. They will have been engineered at some point, especially if there are multiple positive effects from the organisms.

Perhaps there's legends about the "gods" making it so that species could survive on their home planet.

And of course there's always the "fun" of them going wrong...

  • $\begingroup$ No room for Legends I’m afraid. We happen to be discussing the very first sentient species in all of existence. And yes, I’m afraid things do go wrong at one point. A defect in an evolved system causes the second greatest disaster of their species not long before they technologically advance towards space flight. It results in a massive loss of life and is yet another way that their biology and history is relevant to the present plot. $\endgroup$ Dec 9, 2019 at 20:13

Bacteria come close to what you are seeking.

Bacteria have a couple of qualities that lend themselves to rapid adaptation.

1: They are small. So they do not need a lot of resources to reproduce an individual. Or many individuals, very fast.

2: Hypermutation as adaptive strategy. If your current strategy is working well it makes sense to repair mutations so they don't screw up your winning plan. But some bacteria can allow hypermutation in stressful circumstances to improve the chance that one or more mutant progeny will have adaptions that allow it to survive in the hostile environment.

3: Uptake of foreign DNA. When in Rome do as the Romans do. If you find yourself in a hostile environment, steal tricks from the natives. Maybe your inherent good looks and wilyness combined with a few stolen tricks will let you outcompete the bastards. Bacteria do this. They find DNA shed from dead organisms in the environment, take it up and try it.

I am afraid, though, that you want some xenomorph supersoldier, not a sweet plate of fragrant Pseudomonas. Consider adapting these bacteria tricks to your supersoldier beast. Start small while you are sorting out the body / physiology plan and then go big once your plan works. Fast replication and multiple sloppy iterations in hopes of one good one (cull the failures and recycle their resources, maybe by eating them). Plus you will have a slew of cool mutant minis for your story. Steal tricks from the locals and then do them better than they do.

  • $\begingroup$ I don’t suppose you know anything about Neoblast cells and how they relate to this Hypermutation you describe? Are they almost one and the same? Super soldier is perhaps a strong word, their physical adaptions to living in and slowly transforming Hell aside, part of the need for their nightmarish evolution is to express the need for peaceful relations between them and for peace to become the standard for social evolution. Like in sexual selection; a bird showing colourful feathers is preferable to sea elephants head butting one another when any wound in such a tough world is likely fatal. $\endgroup$ Dec 10, 2019 at 21:23
  • $\begingroup$ ...slightly off topic but I love telling a good story, lol. $\endgroup$ Dec 10, 2019 at 21:25

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