Tena koutou e taku hoa aroha (that means “greetings to you my dear friend” in Maori — see not just a biologist but a cunning linguist as well)

Welcome to today’s fun fact. We are going to be looking at the wonderful world of BIOLUMINESCENCE (I warned you).

Bioluminescence is a form of chemiluminescence where light energy is released through a chemical reaction and there are quite a few animals that are able to do this.

Now when people think of glowing animals I imagine the first ones they"d think of would be your fireflies and your glow worms. These ones are actually pretty unique, because very few animals that live on land can use bioluminescence. Actually, 80% of animals that can are found in the sea.

We mentioned before that there is NO light at ALL in the sea once you go down below 1,000m. That means being able to make your own is pretty handy because you can use it for all kinds of things. You can use it for camouflage, you can use it to catch prey , to find mates , to yeet yourself away from predators.

Camouflage.

Now you wouldn’t expect to be able to use light to camouflage yourself but hear me out.

This is called counter-shading or counter-illumination. Basically by producing light on the underside of you, you prevent a silhouette from forming relative to the light that filters down from the surface. Like this:

Catching prey

Bioluminescence is super helpful to catch prey. You might remember the infamous example from the wonderful Finding Nemo of the anglerfish that uses its lovely little glowing barbel and then BAM.

You’re lunch.

Also there’s a pretty cool fish called a stoplight loosejaw , which is a type of dragonfish (we all aspire to such levels of coolness). They have a pretty sick use of bioluminescence. Firstly though, let’s have a little recap of the effect that water has on light.

Blue wavelengths of light travel best through water and that’s why the sea is blue. All the other wavelengths of light get filtered out. So that means that by the time you get down to those deep parts of the mesopelagic (the twilight zone) anything red or orangey coloured looks a bit rubbish. That’s why so many underwater photographers use red filters, this is an example of a picture of a coral taken without and then with a red filter.

So long story short — fish eyes normally don’t see red lightbecause why would you? If red lightdoesn’t reach you in the water, being able to see it is totally useless. BUT this stoplight loosejaw has a bit of a lifehack.

It can see red wavelengths of light. Now I know what you’re thinking,

Flora it’s a fish that lives 500m below the surface NO RED LIGHT GETS THERE being able to see it is POINTLESS. You’re so-called “science” is all a lie.

But what if I told you it can make red light using bioluminescence?

So YES that means that this fish can essentially hunt with a torch that IS TOTALLY INVISIBLE TO ALL OTHER FISH SPECIES.

And yes it also has that deep-sea-fish thing of looking like something that was pulled out of the sack that was forgotten under the tree of life.

And this red thing is the light producing organ (called a photophore ).

What’s really weird as well is that the reason we think it can see in red light is that it uses a derivative of chlorophyll to absorb the red wavelengths of light. This sets off a bunch of chemical reactions that can stimulate the visual systems that would normally only see blue light.

But no vertebrates are known to be able to synthesize chlorophyll derivatives so this is really weird. We think it might be that it gets them from the little crustaceans it eats but we’re really not sure.

Not gonna go into a huge amount of detail here because it’s pretty similar to the finding prey thing. Some things glow and that’s really sexy.

Simple as.

(also helps in finding mates when you live in the equivalent of a pitch black room except that room is the size of the UK)

Now things get pretty fabulous here. We’re going to have a quick look at one of my ALL TIME FAVOURITE species — the Vampire Squid.

(I even dressed up as one when I was 14 an age where I really should have known better).

Who wore it better?

This guy has remained unchanged for about 3 million years.

When he’s being hunted by a predator he’s got to do something to get away. If you think what a normal squid would do — it would fire some ink at that bastard. Oh shit wait. It’s totally dark. Not so useful.

NOT TO WORRY.

Instead it will fire a cloud of bioluminescent mucus (try that one out next time you sneeze if you really want to freak someone out) at the predator. This confuses the predator (obviously — who wouldn’t be confused having glowing goop fired at them) and the squid can escape. These guys are very cool though. They have amazing control over their light-producing photophores and can literally turn them on and off like Christmas lights. This means they can make totally fabulous patterns that baffle predators or dazzle prey.

Quite brilliantly, some squid species can even DETACH BIOLUMINESCENT ARMS to stick to their predators. This distracts the predator for long enough for the squid to escape. Again. I"m not surprised. I"d be fucking terrified if someone detached an arm onto me.

This also has the advantage of attracting secondary predators to come and eat the one that tried to eat the squid. Because you know, it’s quite difficult to go into stealth mode when you have A GLOWING ARM STUCK TO YOUR FACE.

Now the squid has effectively signed the death warrant of the predator quite challenging to write without an arm though

Now how the hell do you make the light ?

Well that will have to wait for another instalment. Let me know if you want to know — if not we shall leave the joys of bioluminescence there.

Lots of love and stay glowy,

Flora xx