Recently I attended the latest exhibition at the Museum of Idaho, Glow: Living Lights. I was so excited to go and see this exhibit about Bioluminescence and walked away so very disappointed. The Exhibition was entitled, Glow: Living Lights. I have been to museum and aquarium exhibits with Bioluminescence before and I was looking forward to seeing more examples of living Bioluminescence. I didn’t see any. I saw pictures and about four dead animals in jars, but nothing was living. Here is my dilemma; Bioluminescence literally means living light. It’s a hybrid word of Greek and Latin origin, the Greek “bios” means living and the Latin part “Lumen” meaning light.
There were no “living” lights. There were pictures and dead things that no longer illuminated, videos and a lot of information that I’ll be giving to you, but nothing about this exhibit could be called living. I think that needed some clarification. I almost didn’t write this article because I’ve never written a bad review of a museum exhibit before. It wasn’t even a very bad exhibit, just not what was expected.
Now I think it’s time to actually talk about Bioluminescence. In essence (I’m so punny) Bioluminescence is a form of luminescence, or a “cold light” that is emitted by a living organism. Less than 20% of the light will generate any kind of thermal (heat) radiation. So it shouldn’t be confused with Florescence, phosphorescence, or iridescence.
Bioluminescence is actually a form of chemical luminescence. That means that a light energy is released by a chemical reaction. The chemicals luciferin (a pigment) and luciferase (an enzyme) are produced by Fireflies, Anglerfish and other such creatures. Luciferin reacts with oxygen to create light, while luciferase acts as the catalyst to speed up the reaction. This chemical reaction can occur either inside or outside of a cell.
Bioluminescence occurs widely in some animal groups, most especially in the open sea. It can be found in some forms of bacteria, and in some fungi. Glowing fungi isn’t all that unusual in nature and there are 71 known species. But, scientists have re-discovered one of the most strongly bioluminescent mushrooms that has been known to man. It was rediscovered 170 years after the first sighting of the Agaricus Gardneri. Bioluminescence is also found in various terrestrial invertebrates, including insects, notably the firefly. Many of these, and perhaps all of the deep-sea creatures, as well as some bacteria produce light. The Agaricus gardneri mushroom is so bright that it is said if you put some in a dark room you can read a newspaper by it. The local people of São Paulo, Brazil are so familiar with this mushroom that they call it “flor-de-coco” or flower of the coconut because it grows well on the rotting fronds of the dwarf palm tree. A genetic analysis of the fungus allowed those scientists to give it a bit more precise name: Neonothopanus Gardneri.
As I said before many of these creatures produce light, most marine life give off a blue and green color in the light spectrum. The wavelengths that pass through sea water making them virtually invisible. However, it’s been found with the loose jawed fish that they emit red and infrared light, while other species have been known to emit a yellow light. It’s also come to the attention of scientists that sometimes thousands of square miles of ocean surface will shine with the light from bioluminescent bacteria. This effect is know as mareel or the milky seas effect.
There are of course creatures of the non-marine variety that are also bioluminescent. The two creatures best known for their bioluminescence are glow worms and fireflies. There are others, of course, including spiders, insect larvae and fungi. Some forms of bioluminescence are brighter, or exist only at night which often follow a circadian rhythm.
Now that you have a general knowledge of bioluminescence, I’ll explain some ways in which it’s used. You didn’t think it was all about the pretty, pretty, flashing lights did you?
First there is what’s known as “Counter Illumination or Camouflage”. Many animals of the deep sea, including several species of squid, use this as a way to avoid becoming prey. The animal manages to match itself to the overhead light and pattern that would be seen from below. These animals have photo receptors that control how much illumination would be needed to match the background brightness.
Second is Mimicry which is another way bioluminescence is used. For instance the anglerfish dangles an appendage out from its head. He uses that appendage like a fishing lure to attract small animals and once they are within striking distance the anglerfish now has a meal! Another fish that takes advantage of this type of bioluminescence is the Cookiecutter shark. The underside of the shark is bioluminescent while a small portion of the fin is not. Mackerel and tuna think the small part of the fin are small bait fish and they go up for a bite. They are then bitten by the shark that takes a nice round bite out of the bigger fish, leaving a cookiecutter mark on the fish, hence its name!
Female fireflies sometime mimic a light pattern of another species of firefly attracting them as prey. They have also been know to mimic the males of that same species.
Third, Bioluminescence is used to attract a mate. The use of bioluminescence to attract a mate is seen actively in fireflies, which use the periodic flashing in their abdomens (not their rears as you may have thought) to attract a mate in the firefly mating season.
Attracting a mate in the marine environment is also a place to use luminescence. It has been well documented that ostracods, which are small shrimp-like crustaceans, use luminescence to attract a mate.
Fourth, Bioluminescence is used as a distraction. Certain animals such as squid use bioluminescent chemical mixtures in the same way many squid use ink. A cloud of luminescent material is expelled and you now have a predator either distracted or repelled, giving the squid time to escape to safety.
The fifth use of bioluminescence is that of communication, which plays a role in the regulation of luminescence in some bacterial species. It is known that they can turn on genes for light production.
The sixth use of bioluminescence is predation. We’ve talked about how some species in the depths of the sea, such as anglerfish and the cookiecutter shark use bioluminescence to help them hunt. It’s also know that the dragon fish will use it as a lure to attract small fish to prey on them.
The last know use would be that of illumination. We know that most marine bioluminescence is green to blue, we also know that the Black Dragonfish produces a re glow. This allows the fish to see red-pigmented quarry, which would usually be invisible in the cold depths of the ocean enviroments where red light has been filtered out by the water column.
So while I saw no “living” lights at the museum this time, I did learn a lot about bioluminescence or “Live” “Lumen”. I love science and as disappointed as I was in not being able to see the live fireflies, glow worms, and jelly fish, I still took a lot of information away with me.