Let it Glow
Welcome to Season 8: Bioluminescence
Nature Stories is back with a whole new season of stories to share. Season 8 comes from a suggestion made by a good friend, Rachael Levine. It’s also something that we’ve mentioned before, albeit briefly, for a story during Season 4: Mimicry. In that story, we looked at an aggressive mimicry strategy that occurs in a particular genus of fireflies. This season, we’ll be focusing on the particular source of the mimicry from that story: the light patterns of the firefly.
Fireflies glow due to a chemical process know as bioluminescence. While visually similar to phosphorescence (the process exhibited by most common ‘glow-in-the-dark’ objects), the two are quite distinct. The latter simply involves a substance absorbing energy and then slowly releasing it over time in the form of light. Bioluminescence is much more similar in its process to a glow stick in that light is emitted as the product of a chemical reaction, but it is still slightly different because it must be catalyzed by an enzyme.
Bioluminescent enzymes are known by the generic term ‘luciferase’. They catalyze a chemical redox reaction that occurs to a light-emitting molecule or ‘luciferin’. In each reaction, the luciferin is oxidized and loses electrons. This process emits light. The structure of the various luciferins is relatively similar between bioluminescent species, but the luciferase enzymes are much more diverse. Genetic evidence from the codes for these proteins indicates multiple independent developments of bioluminescence throughout evolutionary history (a minimum of 40 separate times).
Some organisms have achieved their ‘glow’ via symbiotic means (recall some of our stories from Season 2: Symbiosis), usually through ingesting or otherwise incorporating light-emitting bacteria. However, there are many species, including fireflies, which can produce their own light without the need for such a symbiotic partner.
There are a variety of different uses that a light-production process can have in a natural setting. Our previous story looked at the idea of mate identification and predation as potential applications for it. Over the course of Season 8, we’ll look at a wide variety of bioluminescent organisms that use it for defense, communication, camouflage, mimicry, and even just simple illumination. The vast majority of organisms that possess these chemical reactions are either nocturnal, crepuscular (operating at dawn or dusk), or marine organisms that inhabit the deep ocean where light does not penetrate. These are the organisms that could derive a benefit from being able to emit light. For an organism that is already active during the day, the effectiveness of an additional light source is reduced.
As always, I hope you enjoy this season and the further fascinating stories that we’ll get to share together. If you like my writing, please share it with others who you think would also appreciate it. I am also interested in you feedback with regards to anything in particular: my writing style, my choice of topics, etc. Please let me know what you think.
Season 8: Bioluminescence Table of Contents
Week 1: Burning With Cold Fire
Week 2: From the Depths
Week 3: Keep Away From the Light
Week 4: Signals in the Dark
Week 5: Welcome to My Web
Week 6: Squid Pro Quo
Week 7: Slime Time
Week 8: No Peanut Butter Required
Week 9: Waving Hello
Week 10: I’m No Shrimp
Week 11: The Smallest Glow
Week 12: Taking a Bite Out of Prey