Let’s keep things simple two rules.
- No giving sentience, This is a no brainer issue.
- Let’s keep it to beings under the Animilia kingdom. “mutated virus/bacteria” is a common trope.
To start:
Let’s modify ants to have lungs.
Most insects are constrained by the amount of oxygen they can acquire through their exoskeleton.
Imagine how big they can get if they didn’t have that constraint?
Mhh, insects in general IIRC are also constrained by the fact they have exoskeletons: i.e. their internal organs are just in a bag. So they can’t grow too much or they just squish I think.
Imagine them being able to become vertebrates. You can have insects the size of cats I think before the osmosis breathing tubes they currently have are not a thing. Lungs would be the next thing I guess.
Disclaimer: I’m not a biologist and just make stuff up from what I remember from high school biology, and it was last millennium!
According to my sister-in-law’s then boyfriend (who was a biologist or an insect guy or something), spiders and insects can have lung-line organs called book lungs. So they have options. Creepy buggy insecty options.
Oh right, I’ve read about that on coconut crabs I think. There you go, they are already half there.