Beautiful Bioluminescence

Throughout the animal kingdom are fairytale-like creatures who have the ability to twinkle and glow. they do it to find love, to find food and to find safety.

Waitomo Glow Worm Caves, New Zealand. Photo by 2il org. Used under CC by-SA 2.0

Waitomo Glow Worm Caves, New Zealand. Photo by 2il org. Used under CC by-SA 2.0

THE BIOLUMINESCENT BREAKDOWN

Have you ever mucked around with a glow stick before? You take the stick in your hands, give it a crack and, voila, you’re ready to disco! Or join the Jedi.

When you do that ‘crack’ you break a small glass vial inside the stick which allows two liquids to react and when they do, they produce light. This type of reaction has the groovy name of chemiluminescence.

Bioluminescence is a type of chemiluminescence that occurs inside living organisms. Most bioluminescent organisms are found in the ocean and it is believed that almost all deep sea organisms who live outside the reach of sunshine, can produce their own light! These organisms have great control over when and why they light up and they usually do it for three reasons - to find a mate, to find prey or to defend themselves against a predator.

LIGHT FOR LOVE

Photinus sp. in Fight, Emitting a Light Signal. By Terry Priest. Used under CC BY-SA 2.0.

Photinus sp. in Fight, Emitting a Light Signal. By Terry Priest. Used under CC BY-SA 2.0.

Be honest - have you ever been caught showing off because you’re trying to impress someone? Maybe someone you have a bit of a crush on? Don’t worry, it’s only natural. Plenty of other animals are guilty of it too.

In the dark depths of the ocean lives a species of octopus called Bolitaena pygmaea. When the females are old enough to start mating they will develop a glowing ring around their mouth; sort of like a bright, shining lipstick. They have it ‘turned off’ most of the time but it lights up when they are near a potential mate.

And it’s not just the ladies glowing for attention. Amongst fireflies it is the males who use their bioluminescence to attract females. Both genders have a light producing organ called a lantern which they use to communicate, by making quick flashes of light like a strobe light at a disco. Some studies show that females tend to prefer the males who flash more brightly and for longer. After the male flashes his light-show he waits to see if the female flashes back and then it’s time to make his approach. The pattern of flashes is different amongst each species which stops them wasting time flirting with a firefly in the dark only to find out when they get up close that she’s actually a different species to him. Awkward!

FLASHING TO FIND FOOD

While it’s great for helping to find love, there is also a dark side to bioluminescence!

Remember that scene in Finding Nemo when Dory found herself distracted by the bright, beautiful light… only to find it dangling down in front of the mouth of a hideous predatory fish? Well, that scene got something right… and something wrong. That scary looking fish is a real (and, lets be honest, really awesome) fish known as an anglerfish. However, the chances of Dory meeting one are unlikely. Blue Tang like Dory, otherwise known by their fancy scientific name Paracanthurus hepatus, like warm shallow water, whereas all 200 species of anglerfish are found in the very dark, very cold ocean depths.

The anglerfish themselves aren’t bioluminescent but they have a modified spine that dangles in front of their mouth like a fishing lure and this lure is filled with bioluminescent bacteria. The light from the bacteria attracts the prey towards the fish’s mouth and then, if all goes to plan for the anglerfish, it’s lights out for the prey. It is only the females who have this modified spine, the males don’t need one, and the reason why is a little bit gross (we will tell you why in an article coming soon!).

LIGHTING THE WAY TO SAFETY

It seems only fair that if bioluminescence can help predators catch their prey, then maybe the prey can use a similar strategy to protect themselves, right? Well, I am delighted to introduce you to the deep sea shrimp Acanthephyra purpurea! Now I know you might be thinking that shrimp aren’t really that cool. Well think again, because this animal’s defense strategy is sick. Literally. When the animal becomes frightened by a predator it can expel a bioluminescent liquid (think of it as like a big, bright glowing cloud of vomit) which serves to distract the predator. So, the shrimp can swim away, like a magician disappearing offstage in a cloud of smoke... or in this case: vomit. Ta-da!

WHAT you know now!

  • Bioluminescent organisms produce and emit their own light

    • Most of these organisms live in the ocean

    • The light is generally used to find a mate, to attract prey, or for defense

  • Bioluminescence is the result of a chemical reaction

Sara Keltie