Bioluminescence the light of the ocean

2 of june- homepage

Bioluminescence is a production and emission of light created by a living organism. It is a hybrid word coming from Greek and Latin. Bios means living and Lumen means light, so bioluminescence means living light. It is widely known in marine vertebrates and invertebrates, but it’s also found in fungi, microorganisms and terrestrial invertebrates. On land the best known examples are the fireflies (Lampyridae) and glowworms (Phengodidae). In the ocean it is everything from bacteria and dinoflagellates (a form of plankton) that make the ocean glow, to octopus and fish. Some organisms that use bioluminescence do not create the light themselves, it’s a symbiotic organism living within larger organisms that is the light creator. This is mostly seen in fish in the deep ocean.

We can see bioluminescence when waves break against shore or we kick water at night, it light up. This happens when there are a lot of bioluminescence bacteria or Dinoflagellates in the water. These organisms light up when disturbed. Bioluminescence should not be confused with Phosphorescence.  Phosphorescence is a reflection of light normally seen in glow-in-the-dark toys, paint or watches that glow a while after being in the sun and are more man made glows then the bioluminescence.

Bioluminescence is a form of “cold light” with less than 20% of the light generates heating. It’s not used to heat the body it used for counter illumination, mimicry, distraction, attracting mates, warning, and illumination.

In the camouflage post last week we explained most of these examples, but when using bioluminescence it works a little bit different.  Using bioluminescence for counter illumination works the same way when having a light belly that matches the overhead environment, and darker back to match the dark water/land below. This is normally used by fish or squid that have special organs with bioluminescence bacteria that will regulate the brightness to match the incoming light.

Mimicry is mainly used by predators to attract food. The best example of this is the Angling fish (Lophiiformes) that have an appendix sticking out from their forehead with a bioluminescence bacteria filled organ. When this organ lights up the prey will be attracted to it in a trans-like state and the Angling fish can almost get them to swim straight into their mouth. To use bioluminescence as a distraction is normally used by prey to make the predator think they are dangerous. Having bright colour in nature is normally a sign of being poisonous and this is what the prey tries to do.

Fireflies attract mates by flashing their back bodies in breeding season. A tiny shrimp (Ostracoda) also flashes to attract mates over long distances in the ocean. Illumination is actively creating and using the light to locate the prey. Black dragon fish (Stomiidae) produces a red light instead of green or blue, this is because the first color that fades the deeper you go in the ocean is red. Having red pigmentation in the depths makes you disappear. When the Dragon fish uses the red light they can see their prey with the red pigmentation, but the preys eyes are not adapted to see red light so the dragon fish will catch them unexpectedly. There are some predators that can see the red light so the dragon fish turn its light on and off to not be eaten themselves.

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