Why would a virus evolve to subsist on an energy source that doesn't exist on their planet?

Question

In my world, I have a dangerous virus that has evolved to subsist on Aether, which for now I will just call its secondary energy source apart from a normal infection of an animal. Yet on the planet where it evolved, there is no Aether to be found. Why would it have evolved these capabilities?

Solutions I have so far... Since Aether is an incredibly powerful energy source biologically and chemically, perhaps in a bygone age where Aether was common on the planet the virus's ancestors evolved the ability to feed on it. The capability was sustained in its biological makeup, long after the Aether had run out.

*Edit Oof, I completely forgot Biology 101. By subsist on Aether I meant it targets creatures that contain, eat or are a carrier for Aether. I'm sorry for the confusion with the virus 'feeding'. My question was why would it target these Aether-rich animals when there was none on its home planet.

Answer 1

Because the Virus has consumed all the Aether on their planet. As it ran out, the virus evolved to use alternative sources, and once it ran out, only the viruses that developed alternative methods of gaining energy remained.

Answer 2

Viruses don't "subsist on an energy source" at all. They are just molecules that have a malignant effect when they come into contact with organisms. When they are outside of the body, they just exist without any sort of metabolic activity whatsoever, and a viral infection is entirely fueled by the host which is tricked into using its own power to replicate the virus.

As such, a virus would not evolve to use aether. Instead, it must evolve to attack the genome of an organism that does use aether as a power source.

This leads into the second issue which is that viruses are generally species specific. Where as an organism can eat a strange creature and do its best to break it down into usable molecules, viruses need to bind themselves to cells that already have the exact genetic sequences required by the virus. In nature, a virus can sometimes jump species because both species share a common ancestor with nearly identical genetic code in just the right place, but jumping between two species that evolved on different worlds is just not going to happen.

The only way I could see a virus interacting with aether at all is if the alien species decided to incorporate some of the genetics from a local species into their own genome and inadvertently made themselves carriers for the gene that the virus targets.

Answer 3

Virus evolve very quickly.

You can very easily get away with saying they evolved very soon after arrival.

On the other hand, a "bygone age" sounds like it is very unlikely that they have kept that ability. Why? Because virus evolve very quickly.

Of course there is also the factor of how fast they reproduce. The virus will reproduce very, very fast, on an acute infection. Thus, I would say that they evolved the ability to survive※ and take advantage of an Aether rich environment very soon after they infected patient zero.

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※: not sure if that was a problem.

Answer 4

It wouldn’t.

To evolve is—-by definition—-to be come better suited to live in the current environment. If your virus became compatible with an environment that it is not currently in, there could only be two explanations:

1 - it was a coincidence, the trait they gained both benefited them in the present and will benefit them in the future.

2 - someone was consciously meddling with their evolution, planting latent traits that is currently useless but will be useful later while somehow wiping out competitors that do not have the trait.