Saturday, June 30, 2018

Bioluminescent Animals: Land and Sea

Have you ever collected fireflies in a jar on a summer night?  These little insects create their special light through a chemical reaction in their abdomen.  This reaction is called bioluminescence. As amazing as this phenomenon is with land critters, it is super fascinating with marine animals. 

Jellyfish Bioluminescence

How Do Marine Animals Create Bioluminescence?

Just like the fireflies, marine animals create bioluminescence through a chemical reaction.  In order for a marine animal to create bioluminescence, its body must contain a special molecule called luciferin.  Whenever luciferin reacts with oxygen it produces light.

Which Marine Animals Have Bioluminescence?

This two inch krill is bioluminescent behind its eye.

Bioluminescent animals come in many sizes: 

  • Very small animals like plankton, algae, and bacteria 
  • Small animals like krill, worms, and sea stars 
  • Middle sized animals like jellyfish and fish
  • Large animals like sharks
  • Most deep sea animals

Bioluminescent animals are very versatile. They can adjust the intensity and color of their lights simply by controlling their body chemistry.  

This is seriously cool.  

What Colors Can Bioluminescent Animals Produce?

Light moves in wavelengths. In the ocean, longer wavelengths--like red--can't travel as far as they do on land.  Other wavelengths, like blue and green, are shorter and can move much farther. As a result, most bioluminescent emissions in the ocean are blue-green in color.  However, there are exceptions, as we shall see below. 

How Do Animals Use Bioluminescence?

  • Some animals use bioluminescence to find prey.  

The dragonfish is a good example.  Black animals are almost invisible in the darkness of the deep sea.  Few can see them, except for the dragonfish.

Dragonfish have evolved to emit their own red light.  This red bioluminescence enables them to see black prey that other predators can't see. 

  • Other animals use bioluminescence to attract mates.
Males and females alike will put on a quite a light show to attract an individual of the opposite sex. 

  • Most animals use bioluminescence for protection.
Bioluminescence comes in handy when warding off a predator. A strong flash of light can be very confusing. While the startled predator is wondering 'what happened', his light-producing prey leaves the scene.

One deep sea squid, the Octopoteuthis deletion, is an expert at using these diversion tactics.  When thrust into a dangerous face off with a predator, the squid detaches a few of its bioluminescent arms and sticks them on the enemy.  While the predator tries to rid itself of the sticky arms, all the commotion attracts even larger predators to the scene.  Now that the predator has become the prey, the tricky squid sneaks away to live another day.

Bioluminescence is vital to the survival of marine animals lucky enough to have it.  I hope this article has shed some light on this fascinating subject (pun intended). 

Research Sources:

1.  "Bioluminescent Ocean".  Web.  27 Jun. 2018.  Ocean Today.  National Oceanic and Atmospheric Atmospheric Administration (NOAA). <>.

2.  "Bioluminescence".  Web.  27 Jun. 2018.  Ocean: Find Your Blue.  Smithsonian.  <>.

Image Credits:

1.  "Jellyfish" by Pablo Martinez on Unsplash.    

2.  "Fire flies" by newarta is licensed under CCO Creative Commons.

3.  "Antarctic Krill" by Dr. Wayne Trivelpiece Image ID: fish8177: National Oceanic and Atmospheric Association (NOAA): Fisheries Collection.  NOAA NMFS SWFSC Antarctic Marine Living Resources (AMLR) Program  

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