I was thinking of a situation in which a creature lives in a region in which the levels of radioactivity varies from harmless to lethal from place to place and time to time. It takes millions of years for the radioactivity of this place to become unpredictable so that creatures can adapt to it over time. Could a creature in this region evolve to have a sensory organ for detecting particle radiation as a survival strategy?
Bit of background.
No single detection method will cover all radiation types. Focus should be on the dangerous variety, gamma rays. You will want portable real-time detection otherwise it will be of little use. Currently only the Geiger-Müller tube conforms. It works by detecting the ionising effect of radioactivity: It applies Argon gas and electricity at around +400 Volts to trigger an "avalanche" effect to emit an amplified pulse. What it actually counts is ionized atoms.
How to convert to a biological mechanism.
What do you have to detect? Basically only the radioactive isotope, the radiation energy and decay products. For the individual of a species, using disposable live tissue is probably too slow a method. Smelling isotope or decay products is probably too specific. So stepping in at undergoing, then detecting ionization is the way to go. You become the geiger teller. This also means the organism needs not to go off-kilter from a natural source of gamma radiation like thunderstorms.
To do this you'll need a lot of energy and rare materials. The end result will be fragile and make the critter easy to catch (and eat).
I predict a very low survival chance for the poor creature. So in effect the answer is, No.
Is that the end of it?
No again. Learning creatures will be able to tell where the danger resides in known territories. How? Either by remembering that this place where Uncle Mark went is a bad place that will kill you later on. Or by knowing that where the glowing moss grows you better walk fast. And avoid the place for lair-building entirely. Better become an expert at burrowing species at large, to be in the know anywhere.
From https://en.wikipedia.org/wiki/Effects_of_the_Chernobyl_disaster#Plant_and_animal_health: Using robots, researchers have retrieved samples of highly melanized black fungus from the walls of the reactor core itself. It has been shown that certain species of fungus, such as Cryptococcus neoformans and Cladosporium, can actually thrive in a radioactive environment, growing better than non-melanized variants, implying that they use melanin to harness the energy of ionizing radiation from the reactor.
So in effect you get to a radiation proof habitat.
Finally a thick skin seems to be mandatory in this environment. Just to help having more time to detect, avoid. That or breeding like hell. No real use mentioning the last, it is already in place.
So I asked some biologists in my family and they all said: Yes, I imagine it possible.
My quick internet-research didn't show any animal that was currently able to sense radiation, but:
- There are multiple highly-resistant bacteria.
- Wildlife flourishes in "high"-radioactive zones (read: Chernobyl & Fukushima)
From the Wiki-Article:
Deinococcus accomplishes its resistance to radiation by having multiple copies of its genome and rapid DNA repair mechanisms. It usually repairs breaks in its chromosomes within 12–24 hours by a 2-step process. First, D. radiodurans reconnects some chromosome fragments by a process called single-stranded annealing. In the second step, multiple proteins mend double-strand breaks through homologous recombination. This process does not introduce any more mutations than a normal round of replication would.
How would such an organ work
A method I can think of is using the method of Deinococcus radiodurans. Whenever damage in the cells is repaired, a by-product is created. This by-product is recycled over time. The concentration of the by-product in the cell creates a nerve-signal, allowing to "feel" the radioactivity. Ultimately this could lead to eye-equivalents. Instead of photo-sensitive cell-patches you would have radiation-sensitive patches.
The nice thing is that you don't need this mechanism in all your cells. Skin-cells for example would be enough, as $\alpha$-radiation has a hard time penetrating it and every other radiation will penetrate you regardless where you look in your body.
I don't know how feasible that is, especially having only a few cells with multiple copies of the genome. Your best bet would be that every cell has this mechanism, but this would need huge amounts of energy and resources for that organism (probably).
We may have one already: our noses.
What radioactive minerals emit is called ionising radiation. It knocks electrons off neutral oxygen and nitrogen molecules creating charged ions, which are highly reactive. Highly reactive things in even very small concentrations smell pungent.
I don't know whether air in caves or mines smells different if the surrounding rock is high in uranium or if the cave is trapping radon. I do know that air in caves and mines smells quite different to outside air. In any case a human nose is a vastly inferior organ compared to a dog's or a rat's nose.
I suspect a dog could be trained to sniff out radioactive sources if there was a need.