back
17 comments
I heard this story on the radio today. They started off with references to fire flys and other creatures that generate light (I dunno the name for that phenomenon) the led into the main story that lots of mammal fur fluoresces under UV light. Not even close to being the same thing. Bad journalism.
You're confusing 2 terms: Fluorescence and Bio-Luminescence.

The title as written is accurate; what's confusing is other articles sometimes conflate these two things, and so some people also mix the two terms up.

Bananas fluoresce; squid bio-illuminate.

The person you are responding to is specifically complaining that when the research in the article was discussed on a radio program, it confused fluorescence and bio-luminescence, so I'm not sure why you are explaining the difference to them.

(I guess you think they are talking about the article but they explicitly said that they are talking about a story on the radio so I'm not sure where the confusion is coming from.)

>Bad journalism.

That seems harsh. Couldn't it just be a fun general discussion of how light in nature among animals is observed?

No - a TON of things naturally fluoresce when excited by external photons. The size range of proteins is great for that. Proteins that produce light through phosphorescence are a completely different thing and shouldn’t be hand waved into the same category. Some exception could be made for molecules like gfp, etc.
Ever watch CSI? Lots of organic fluid will fluoresce under a strong UV / blacklight.

Very, very different than bioluminescence. It is mildly interesting, but the comparison is really misleading.

> (I dunno the name for that phenomenon)

Bioluminiscence.

Fluorescence is one way to defend against the harmful bond-breaking abilities of UV light.

I suspect in many cases it is simply the biologically cheapest 'sunblock'.

Most mammals have no concern for UV damage, as they're covered in fur.
When young, the fur often hasn't grown yet.

Also, the fur itself may degrade in UV, making it weaker, fading, and losing waterproofing and other properties the animal relies on.

And finally, the cost of fluorescence may be very small - meaning that it may have had some benefit at some point in the past, but there now no selective pressure to get rid of it.

Why is it on the belly then and not on the back? Countershading?
Many non mammals have vision that includes UV (birds, reptiles, insects ... ) if any of these hunt the mammal, fluorescence may be a way of not reflecting light the predator can see. Fluorescence must emit a lower frequency and intensity of light than could have been reflected
I have learnt that platypuses glow in the UV light from, well, https://www.youtube.com/watch?v=Zxf2MgYCOm0
So this just means that they reflect uv rays not that they have some sort of glow in the dark system recharged by the sun during the day to help them see at night.
Bit more complex than reflection. Reflection preserves the wavelength. Fluorescence is where light is absorbed, some energy is transformed to heat/motion, and then photon is re emitted at a lower energy. In UV fluorescence the initial wavelength is invisible and the final one is visible. Technically you can visible to visible fluorescence also, but it’s less impressive to us.
And then there is multi-photon fluorescence where several low energy photons are absorbed simultaneously to pump up the electron state and then it can emit a higher energy photon!

This is used in a lot of biomedical imaging with infrared illumination yielding visible wavelengths.