Inspired by today's XKCD comic

hazard sign

How could a creature, momentarily called XKCDius lethalissimus, evolve to have the following features:

  1. Be radioactive (intended as more radioactive than the environmental background)
  2. Give high voltage hazard
  3. Emit laser
  4. Be a biohazard
  5. Be slimy enough to make a floor slippery

If laser emission is not feasible, I can settle for just incoherent light emission.

This is my contribution to the Anatomically Correct series.

  • 4
    $\begingroup$ @Demigan: or conversely, take in radioactive ore as an ionising source in order to generate a static voltage. I suppose it could emit light as excited electrons drop down into the valence band, but that would hardly be a laser $\endgroup$
    – nzaman
    Commented Aug 28, 2018 at 15:41
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    $\begingroup$ 😆 Please clarify what level of biohazard you require for a best answer. Given my experience with my two younger brothers, I can assure you flatulence is a biohazard. $\endgroup$
    – JBH
    Commented Aug 28, 2018 at 15:43
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    $\begingroup$ Related to the biological laser part: Can a biological laser exist $\endgroup$
    – Dubukay
    Commented Aug 28, 2018 at 16:03
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    $\begingroup$ Sorry, voting to close as Do my work for me. I don't think it has enough information and I see no effort. worldbuilding.meta.stackexchange.com/questions/2797/… $\endgroup$
    – user3106
    Commented Aug 29, 2018 at 8:27
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    $\begingroup$ VTC: Too broad. I count five questions here, with the third one on lasers being a dupe of worldbuilding.stackexchange.com/q/58944/21704 $\endgroup$
    – Anketam
    Commented Aug 29, 2018 at 18:47

11 Answers 11


I can see evolution provide 1, 2, 4, and 5. 2, 4, and 5 all occur in nature now. 1 could be explained by other means. We are going to have to stretch to get the laser working.

As a base creature, we could start with some sort of Amphibian. Most Frogs, newts, salamanders and such can produce mucus of varying properties. One of them, in the case of poison dart frogs, is a strong alkaloid toxin. That gives you a bio-hazard. A big frog could also give your slip and fall hazard by leaving the mucus all over and if it doesn't evaporate quickly, you could step on a patch and take a tumble. So getting 4 and 5 together is pretty plausible.

Your evolutionary justification for this is some sort of boundary between a swamp and desert. Most likely in a river delta. The massive mucus production helps keep the Amphibian moist when a dry spell or hot wind from the desert threatens to dry our little friend out. The Toxin, and probable colorful markings, would be a warning for any birds that may view him as a tasty snack. 'Eat me, and you won't live long enough to reproduce'

Moving on to number 2. The Voltage hazard. Electric eels hunt by giving a stunning shock to their prey. Lets start with that, and have our little buddy evolve from an electric eel, keeping that electrical charge as its prime hunting mechanism. Remember, cute frogs are actually predators. With a stout shock, a frog may be able to take prey nearly as large as itself a little easier. So keep that mechanism as an evolutionary holdover.

That's 3 down, 2 to go.

Number one on your list, Radioactivity. Higher than background. Here is how we get to that. A little farther up the river there is a mountain with large deposits of Uranium. Rain and erosion wash a lot of this naturally occurring stuff downstream, where it settles deep in the delta where our little lethalissimus lives. He's going to absorb a lot of it as a function of his environment. Granted, it will match the background radiation of the swamp itself, but out of the swamp, his personal radiation will be relatively much higher. However they could also have a form of body chemistry which bio accumulates some of the radioactive daughter products; say strontium-90 phosphorous based bones. Due to higher availability of strontium vs calcium in that environment.

Finally we get to the lasers. sigh. I can't think of any way to produce a natural laser. Fortunately, you left me an out for light emission. Bio-Luminescence. Fireflies do this to draw mates, angler fish do this to draw prey, and so on. So the electric eel that is the forebear of our friend shared some traits with an angler fish with a lure to draw prey into electric stun range at night.

So what we end up with is a large Frog-like creature. Brightly colored with an appendage on either side of its body with a bioluminescent sack to draw prey, like a small bird, into stun range. Bird goes for glowy thing and gets zapped. During the day, other birds get discouraged by the brightly colored pattern that says 'stay away unless you want a terminal tummy ache' due to the highly toxic function of the mucus. The Mucus is produced in large quantities to help keep him hydrated in hot weather. The slow evaporation means slick surfaces every where he goes. And he is Radioactive merely due to the runoff from Mount Plutonium, and bio-accumulation of radioactive elements.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Commented Aug 30, 2018 at 14:14
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    $\begingroup$ Where you have high voltage and biological systems are capable of producing lenses and mirrors to make eyes and biological systems are capable of selectively transporting CO2 and a variety of minerals around, you theoretically have all the parts for an actual CO2 laser available... Natural occurrence seems pretty unlikely though so it'd probably have to be the result of an advanced genetic engineering program of some kind... $\endgroup$
    – Perkins
    Commented Aug 30, 2018 at 23:00
  • $\begingroup$ Toxins aren't biohazards are they? I thought "biohazard" means infectious. That's actually easier, though--it's the carrier for something nasty. $\endgroup$ Commented Mar 16, 2023 at 23:55

taser laser


  • high voltage: check
  • laser: check
  • slimy: wait till you meet him.
  • biohazard: he has scabies.
  • radioactive: he wears a watch with a radium dial.

Evolved to have these abilities: it must be the case, because here he is.

  • 15
    $\begingroup$ Nitpick: They stopped making radium dial watches in the 1960's. The radioluminescent watch dials made in modern times use tiny glass capsules of radioactive tritium gas. $\endgroup$ Commented Aug 28, 2018 at 17:09
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    $\begingroup$ This is my new favorite answer in Worldbuilding. $\endgroup$ Commented Aug 28, 2018 at 17:18
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    $\begingroup$ @plasticinsect Counter-nitpick: ..maybe he wears his grandfather's watch (?) $\endgroup$
    – xDaizu
    Commented Aug 29, 2018 at 6:21
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    $\begingroup$ @xDaizu, maybe his grandfather was in WWII and his father in Vietnam, both wearing that watch $\endgroup$
    – L.Dutch
    Commented Aug 29, 2018 at 9:33
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    $\begingroup$ Instead of the radium, he's carrying a bunch of Bananas that are naturally radioactive. Plus they match the yellow of the Taser. $\endgroup$
    – Criggie
    Commented Aug 29, 2018 at 10:58

Start with the black radiotrophic fungus that thrives in Chernobyl.

It is easy to conceive a drippy, slimy fungus that will cause the floor around it to be slippery, as well as being a biohazard due to the symbiotic bacteria it harbors. In order to give you a jolt, it will need to have electroplaques, just like a unicorn. It could have those in the fungal body, evolved as a defense mechanism against animals that would eat it.

Finally, lasers. There is no way to have those with known biology. But the fungal body may be somewhat translucent to some wavelengths, and act as lenses - specially if the fungal body accumulates silicon and oxygen in just the right way. If you chop it and place it on your backyard, it might even act as a magnifying grass and set the lawn on fire, adding one more hazard to the package.

Alternatively it does not work as lenses nor give out lasers at all. But if it is a mushroom and there are humans around, regardless of its hazards it is just a matter of time until someone eats it. It may be that anyone crazy enough to ingest it will hallucinate and see lasers and other forms of light. The fungus will be known as lasershroom, and will be a favorite amongst the most suicidal psychonauts.

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    $\begingroup$ +1 for also referencing Lightning Unicorns. $\endgroup$
    – aslum
    Commented Aug 28, 2018 at 19:01
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    $\begingroup$ You can get biological lasers - all you need is Bioluminescence and mirrors. link $\endgroup$
    – ltmauve
    Commented Aug 29, 2018 at 15:39
  • $\begingroup$ @ltmauve That's awesome! $\endgroup$ Commented Aug 29, 2018 at 19:24
  • $\begingroup$ @ltmauve I was thinking the bioluminescence route when I read the question--but how do you get a laser powerful enough to warrant a laser warning? You won't have the energy density. $\endgroup$ Commented Mar 16, 2023 at 23:57
  • $\begingroup$ @LorenPechtel, I wasn't aware of that criteria of the warning, thought that makes sense. As for the answer, you wouldn't. The technology is only suitable for imaging, as the components of a cell absorb energy from a laser. $\endgroup$
    – ltmauve
    Commented Mar 22, 2023 at 3:42

This is just a sanity check of how each attribute could be achieved. Not a proposal of a full functioning organism.

I am only providing a sanity check because I do not think this organism would ever evolve. The key reason is that this animal has at least 3 completely separate defense mechanisms, that traditionally use up almost all of an animals body space and resources. Normally evolution would favor making one of these really good, over having all 3. Even if all were effective and dangerous, it would be wasteful to the animal and its species because it is unlikely that all these defense mechanisms would be required for successful survival and reproduction, (the driving force of evolution).

Never the less here are the desired qualities and real life examples. We can mix these together to make the desired organism, and research how these came to pass in order to make up a contrived case for the evolutionary history of this organism.

Be radioactive, more radioactive than the environment : This can be done by having the animal require a large amount of potassium as part of its diet. You can see this in plants with naturally elevated levels of radioactivity: https://www.mirion.com/introduction-to-radiation-safety/naturally-occurring-radiation-norm/

Give high voltage hazard : Evolve an electricity producing organ like the electric eels Hunter Organ : https://en.wikipedia.org/wiki/Electric_eel

Emit laser : This one is probably impossible. At least if it is intended to be dangerous. Of course since a laser is just a focused beam of light, we could pick at the question and create a faint light source that is simply focused, but this seems to be against the question's intent.

Either way, bioluminescence is the best we are going to get. There are too many things that are no goes here for a dangerous laser. How do you store up so much energy? Is using a laser just an incredible waste of resources? Would this ever actually evolve? I think it would not at all, and certainly not on an organism that already has other defense mechanisms like those stated here.

Be a biohazard : As others have stated, be toxic. Like various species of poisonous tree frog, salamander, etc.

Slimy enough to make a floor slippery : Snails are the go to here. Just have a mucus membrane interacting with the floor. In the case of snails it is for sticking. It could be the same here.

  • $\begingroup$ I wouldn't say that thee of these traits are necessarily defensive. Electric shock is used primarily as a hunting tool. Toxicicity can be both offensive and defensive, as a poioson arrow frog uses this trait as a defense, where it is part of the offense of a black mamba. Traits can also be complimentary, like fangs and claws in cats. $\endgroup$
    – Paul TIKI
    Commented Aug 28, 2018 at 17:17
  • $\begingroup$ If they are complimentary it might reasonably happen. If they are antagonistic I think it is extremely unlikely or even impossible to get everything together at once, short of genetic engineering in a lab. $\endgroup$ Commented Aug 28, 2018 at 17:20
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    $\begingroup$ I also come back to creatures like the Tiger Snake. It is both venomous and poisonous. It feeds on frogs and other critters that produce an alkaloyd toxin and storse that toxin in a special sac. It also is venomous, using venom to subdue prey. It's why I can see an evolutionary path, at least for the purpose of building a world. $\endgroup$
    – Paul TIKI
    Commented Aug 28, 2018 at 17:24
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    $\begingroup$ A laser is not "just a focused beam of light", but a coherent beam, where the photons are in phase. A laser is probably the cheapest way to get a focused beam for a pointer, but you don't need a laser for that; on the other hand, you cannot read a CD without a laser. $\endgroup$
    – Davidmh
    Commented Aug 29, 2018 at 12:06
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    $\begingroup$ @TylerS.Loeper I agree with you on the biology, it is just that, as a physicist, calling a laser "just a focused beam of light" irks me. :) But the danger of lasers comes from being focused, not its coherence. $\endgroup$
    – Davidmh
    Commented Aug 29, 2018 at 13:03

All you need is a glowing, shocking banana tree.

Be radioactive – they are already more radioactive than background radiation

Give high voltage hazard - this is the tricky one but using info from this WB answer we know it's possible for organic photo-voltaic conversion so all the plant does is convert excess sunlight into electricity which it stores for future use (or to power its bio-luminescence)

Emit a laser - since you allowed bio-luminescence we have enough plants to adapt this from.

Be a biohazard - make it poisonous

Be slimy enough to make a floor slippery - have you seen a mushy banana ?

  • $\begingroup$ Bananas may be slightly radioactive, but hardly enough to merit a warning symbol. $\endgroup$
    – forest
    Commented Aug 29, 2018 at 8:48
  • $\begingroup$ @forest ehh as per question request all he wanted was more radioactive than background radiation - no mention of needing a warning symbol, though I do see your point in connection to the image now {i missed it due to my poor net connection} $\endgroup$ Commented Aug 29, 2018 at 8:51

Three out of five are pretty easy- slippery, electricity, and biohazard. It'd be pretty easy to concoct an animal that could satisfy those conditions, as they already exist in nature. Something like an electric eel that also has venomous fangs would serve pretty well. However, radioactivity and lasers are much more difficult. While radioactive isotopes of common elements do exist, they're generally found in very small quantities, and there's no way to chemically distinguish them from stable isotopes. So your eel wouldn't be able to, say, accumulate carbon-14 somehow.

Collecting quantities of an unstable heavy element would seem more plausible- there are ongoing experiments with extracting uranium from seawater, for example, so a living creature might be able to do this on its own. However, naturally-occurring uranium is really not that radioactive. In fact, the only way it can really be dangerous is if it's ingested- not because of the increased exposure to alpha particles and such, but because it's toxic and can cause kidney failure. Even if your animal did somehow isolate it in a special organ, all it'd do is increase its own cancer risk, with no discernible evolutionary benefit.

Even if we assume that there's somehow a large natural source of some short-half-life element that this creature feeds on, it would cause far, far more harm to the creature itself than to any predators or prey. Letting highly radioactive substances inside your body is never a good idea.

As for lasers... as Paul TIKI mentioned, probably the closest you're going to get is bioluminescence for purposes of luring prey.

  • $\begingroup$ Enzymes slightly distinguish between radioisotopes. Carbon dating is possible because of the resulting concentration differences. $\endgroup$
    – Jasper
    Commented Aug 29, 2018 at 4:34
  • $\begingroup$ @Jasper Interesting, I hadn't known that. Thanks for the info! $\endgroup$
    – Patrick N
    Commented Aug 29, 2018 at 12:34
  • $\begingroup$ @Jasper No, that’s incorrect: The kinetic isotope effect does exist, and it does affect C14 dating. But C14 dating works because dead organisms stop accumulating carbon altogether (but only losing the radioactive isotope), not because they accumulate them at different rates. $\endgroup$ Commented Aug 30, 2018 at 15:27
  • $\begingroup$ @KonradRudolph -- Thanks for the clarification. $\endgroup$
    – Jasper
    Commented Aug 30, 2018 at 17:12

Adult Lightning Unicorn

This is not the first answer I've written about Lightning Unicorns, but TLDR they fire lightning along a laser channel. During the refractory period after firing their laser the Lightning Unicorn absorbs ambient heat at a prodigious rate. This temperature drop generally causes condensation in the immediately area. In a meadow this leaves a large dewy area, often thought to have mystical properties, in addition to the slip factor. And of course everyone knows that the Lightning Unicorn's horn laser is a Nuclear Pump laser, so extended proximity should probably be avoided.


Did you mean Dripping Bonnet?

So as it turns out, there's already a species that essentially meets all your requirements. In specific, the Roridomyces genus of Fungi seems to contain a lot of the requirements but Roridomyeces Roridus, or dripping bonnet, has the most in one place that I can find.

Let's go down the list one at a time.

  • Radioactive: Now, all species tend to have some amount of potassium inside their cells. In the case of dripping bonnet, there isn't necessarily a higher concentration then most other plants, but one growing in a potassium rich soil could easily be classified (as very very slightly) radioactive.

  • High Voltage: As it turns out, all plants are high voltage. Yes, I know it sounds weird, but hear me out. You know that potassium that all plants have from the Radioactive portion of my answer? Well potassium is used inside plant cells to create an ionic difference between the inside and outside of the cell. That means plants can use it to deploy small electrical impulses. The debate over what these impulses do is still ongoing, but by their nature as static electric fields, they may be considered high voltage. I am having trouble figuring out how to properly calculate voltage, but I do know the resting voltage between cells is 70 mV, with each cell being around 10 Micrometers.

  • Emit Lasers: Turns out these little guys are Bioluminescent. Now, I know that that's not technically a laser, but lasers don't exist in nature, so light emitting is pretty good all in all. It's been suggested that the luciferin which makes the bioluminescence happen, can actually be used as a liquid laser substrate. If the cone can be considered a collimator (albeit a poor one) that makes a mushroom kind of like a laser, depending on the frequency emitted by the luciferin.

  • ☣ BioHazard: Unfortunately, our mushroom fails to pass the biohazard test. Simply put, they aren't designed to infect humans. Sure, a sick human may be able to contract them, but a biohazard is typically considered an infectious agent that can infect a healthy human.

  • Slimy: This is the big perk of Dripping Bonnet, it secretes a sticky liquid. They're pretty small, so it probably rarely happens, but a grouping of them could definitely make a slippery spot on a floor.

So there you have it, a single mushroom already meets four of five criteria. However, Biohazards are hard to find, considering toxins usually end up classified as a Hazard rather than a biohazard, according to UN Standards. Fungus are one of the few biohazards that aren't either viral or microbial though, so that at least puts it as close as possible.


As others have noted, you are basically searching for a poisonous frog which hunts using electric shocks like electric eel do. I have an improvement to offer for the light emission (see note below) and radioactivity to add:

The Lethalissimus has a special organ for its luminescence: It's a patch of skin on its back that both accumulates radioactive materials from a possibly already enriched environment, and which also contains a dye that turns the radioactive radiation into light. For the frog, this has the advantage that it does not need to expend energy to keep its light glowing, it just needs to accumulate enough material. The glowing is, of course, part of Lethalissimus' strategy to avoid predators: A visible yellow glow even by day should be enough to make any bird think twice about its choice of a snack...

Note: Real lasing is pretty much out of the question. Lasers require very high power densities which are not found in biology. And small (= size of typical creature) lasers require a laser cavity between highly reflective mirrors, which are also not found in nature. There are really some quite strange creatures out there, but I'd find it hard to believe a lasing one to exist for these reasons.


Since the other aspects have been well handled already, I'm going to focus on the laser. Although lasers are not known to exist in the biological world, I think a biological laser might be possible. A biological laser would likely be similar to engineered chemical lasers, creating excited states of molecules by chemical reactions. Your eyes have optical quality lenses, so focusing the beam should not be a problem either.


I can't imagine it actually evolving but I can see an evolutionary path:

First, we need a young planet that condensed from a reasonably recent supernova. This is to produce a sufficiently high concentration of U-235 that natural uranium can sustain a chain reaction. (This happened a couple of billion years ago on Earth, thus it's possible.)

1) I do not know why the creature wanted a block of uranium in it, but for some reason it did. The climate turned too cold, it evolved to use a low grade fission reaction to keep from freezing--and developed enough radiation resistance that most of the creatures aren't killed by their reactors.

This is also a major defense system for the creature--the creature controls the reaction to maintain fission at a low rate but if it's eaten the reactor might run hot--pretty dangerous to whatever was trying to eat it.

2) We already have the example of an electric eel.

3) There is another thread about biological lasers--but why? We don't need a weapons grade laser--our creature is an air-breathing swamp dweller. So long as the laser can ionize it's path it provides a way of projecting it's shock weapon a short range--the outgoing bolt follows the laser, the return path is the swamp itself.

4) Trivial--it's a carrier of something deadly.

5) It's skin needs protection from the drying air--plenty of such creatures are slimy.

We have two spots that are going to be very hard to evolve--one would be very unusual, both in one creature probably would never occur. However, I wouldn't consider it utterly impossible.


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