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A small creature I have in mind is highly toxic and constantly glows as a distinctly visible warning to everything else at night. It would use other warning methods but they're not really visible in the dark and is only active at night due to its nocturnal nature.

It is an insectivore scale-less reptile that has a similar body build to a gecko and has the ability to glide if it needs to.

The constant glowing skin is from the luciferase pumping through its veins and is produced by an organ specifically dedicated to do so. While I know organisms can produce luciferase, I don't know how metabolically expensive it is and if its constant production is feasible.

Is it feasible for an animal to constantly produce luciferase for bioluminescence purposes or would it be at risk of going into a metabolic or nutritional deficit because of it?

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  • $\begingroup$ A quick question. Why do you want to rely on sight and possibly colour in the night, where most creatures have evolved to rely on other better senses? I'm not saying it won't work, but wouldn't sound and smell both be more easy and practical? $\endgroup$
    – Trioxidane
    Dec 7 '21 at 8:48
  • $\begingroup$ you are forgetting fluorescence, some animals glows when hit by certain wavelength of light ;D $\endgroup$
    – user6760
    Dec 7 '21 at 8:59
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    $\begingroup$ @Trioxidane Most predators only find out a particular animal is dangerous via smell or taste after having come close to it and most likely attacking it. They might not swallow them in the end but the damage in the strike has already been done. Making the warning so obvious at the long range that glowing at night would provide makes it so a predator probably won't even try to attack them. The glow also doubles as a good way to spot mates from afar, where the gliding would come in handy to close the distance. $\endgroup$
    – Rubrikon
    Dec 7 '21 at 9:21
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    $\begingroup$ Edited as per Rogue Ant's suggestion $\endgroup$
    – Rubrikon
    Dec 7 '21 at 13:59
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    $\begingroup$ Nitpick: You also need another chemical, generally known as a ‘luciferin’ in addition to whatever particular luciferase is present to get light. $\endgroup$ Dec 8 '21 at 20:13
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Wikipedia states regarding bacterial luciferases:

The efficiency of many examples of bioluminescence in nature is astounding; with more than 90% of energy input turned into light. By contrast, figures quoted for a 150lm/W LED suggest that around 20% of the total energy used is converted to visible light

Compare to a mouse:

A mouse base metabolism of 0.35 W, if an additional equivalent amount were expended on light production (needing just twice the food for rest metabolism), then it could produce the equivalent of the light output of a 1.5 Watt LED, that's pretty bright (I should add that my favourite keyring-torch is less than a tenth of that power).

Conclusion.

Lizard's rest metabolism is much lower, so the cost in food for that is reduced leaving more spare for lighting effects: no problem.

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    $\begingroup$ Sweet. If they have the potential to be so bright with relatively little increases in food requirements then perhaps I need not handwave so much the terrarium lamps they're used in to save on lamp oil. $\endgroup$
    – Rubrikon
    Dec 8 '21 at 17:23
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    $\begingroup$ Oh, cool. Now I want one I can wear on a lapel (or train to sit on the front of a hat etc..). I call first dibs if you manage to actually breed them. @Rubrikon $\endgroup$ Dec 8 '21 at 17:30
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    $\begingroup$ As mentioned in another answer, there are cave worms in New Zealand that glow 24/7. Doesn't seem prohibitive at all for a lizard. $\endgroup$
    – Zeiss Ikon
    Dec 8 '21 at 20:05
  • $\begingroup$ A 1.5W LED is a serious flashlight, or even if omnidirectional would be enough light to see other things by, vastly more power than needed to glow in the dark. (Are we talking about bright enough to be easily noticeable even in sunlight? That would be metabolically expensive.) I think your argument about lizard metabolism is backwards: lizard lifestyle is based on low energy income, low energy usage. Needing to double your food intake would be bad enough; needing to quadruple it vs. a non-lightbulb lizard would be a huge change. IMO, look at power for an indicator light, not torch. $\endgroup$ Dec 9 '21 at 12:45
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Here in New Zealand we have the NZ glowworm which glows from luciferase all the time, and lives in cold, dark, low food environment (caves) in huge numbers. They're tourist attractions, some huge caves are positively covered in them. And many very deep sea fish are bioluminescent as well, so the signs are good.

Most bioluminsecent molecules are actually not consumed by glowing, they expend ATP to produce an excited state in the bioluminescent molecule itself to do so. Luciferase works this way, it's just a means of using ATP to make light.

I'm an inorganic chemist and couldn't comment on luciferase itself but the luminescent molecules I synthesised in undergrad were not spectacularly complex or energetically unfavourable, no more than e.g. common flavoured and coloured molecules.

You'll have to wait for an exact answer from a biochemist but I bet luciferase is a mundane protein with an interesting but not-fantastically-expensive active site, and in any event, it's the ATP fuel you need to make continuously, not the luciferase itself. It ought to be possible.

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    $\begingroup$ "inorganic chemist" Makes it sound like you're a silicon based lifeform. haha. $\endgroup$
    – DKNguyen
    Dec 8 '21 at 1:40
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    $\begingroup$ I am. I look a bit like the Chenjesu from StarControl. I just smile contentedly when I see posts on my body chemistry in this forum. $\endgroup$ Dec 13 '21 at 2:43

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