Whether it’s for survival (camouflage), communication, or reproduction, nature (and animals in particular) isn’t short of remarkable traits. Some animal’s ability to glow in the dark is one of its most magical displays. Scientifically known as bioluminescence, animals that glow do so for various purposes, none of which is to wow humans, though that is often the case.
Over time, animals with this amazing trait have sparked scientific curiosity and continue to do so. Here, we learn what bioluminescence is, how it works, and popular examples of animals that glow.
What Is Bioluminescence?
The general consensus is that bioluminescence is living organisms’ ability to produce and emit light, especially in the dark. Unlike an electric bulb, animals that glow have natural chemical reactions within their cells. Most animals with the bioluminescence trait inhabit places with low light, including dark forests and deep in the oceans. Bioluminescence is, therefore, one of their most powerful adaptations.
How Does Bioluminescence Work?
As aforementioned, bioluminescence in animals that glow occurs in their cells. It is a chemical reaction majorly involving luciferin and luciferase compounds. Luciferin is the molecule that produces the light, while luciferase is the enzyme that triggers the reaction.
However, the two compounds, though primary, cannot thrive independently. Instead, they require oxygen, ATP, and magnesium, which allow them to produce light without heat. This process is popularly known as cold lighting.
Interestingly, luciferin and luciferase compounds can emit different color shades depending on the animal species and habitat. This explains why different bioluminescent animals produce varying glows.
Why Do Platypus Glow Under UV?
Famous for being one of the few egg-laying mammals, duck-billed platypuses are small, shy animals endemic to Australia. Surprisingly, the animals have recently been discovered to glow under ultraviolet (UV) light.
Apparently, when a platypus is exposed to UV light, it emits a blue-green glow. According to scientists, the mammal’s glow may be necessary for survival in specific circumstances. Glowing allows it to blend with the environment, making it less visible to predators.
What Causes Bioluminescence?
While it’s true bioluminescence in animals that glow takes place within their cells, the bigger question is: what causes it? Well, there are varying reasons for this. For instance, marine animals produce bioluminescence due to symbiotic bacteria that generate light within their bodies.
For others, bioluminescence is caused by evolutionary adaptations. Environmental factors, including oxygen availability, temperature, and depth, may also play a role.
Examples of Animals That Glow
Although many animals glow, some are probably still unknown. That said, here is a list of famous and remarkable creatures known for their captivating bioluminescence.
Anglerfish
Most anglerfish species, especially females, have a luminescent organ called the esca. It is found at the tip of a modified dorsal ray. The esca contains bacterial symbionts that make anglerfish glow.
According to scientists, the glow helps anglerfish lure prey in dark, deep-sea environments where they reside. In other cases, it can be used to attract males’ attention. It is a sign that a female is ready for mating.
Hawaiian Bobtail Squid
While the Hawaiian bobtail squids don’t have glowing characteristics, they have a symbiotic relationship with Aliivibrio fisheri, a bioluminescent bacteria. This bacteria inhabits a specific light organ in the host’s mantle.
Given that the bacteria is the light source, the intensity of the Hawaiian bobtail squid depends on the amount of bacteria in the squid’s mantle. The symbiotic relationship between the two is in such a way that the squid feeds the bacteria with sugar and amino acid solution. On the other hand, the bacteria hide the host’s silhouette from potential predators.
Fireflies
Fireflies are perhaps the most popular animals that glow. Sometimes known as glowworms or lighting bugs, fireflies have soft bodies. They emit light, especially during twilight, to attract males for mating. In other instances, the light may be a warning signal that the insect’s larva is not fit for consumption.
Intriguingly, fireflies have light-emitting organs, usually at their lower abdomens. The light produced is a result of a chemical process called bioluminescence. Luciferase enzyme acts on luciferin in the presence of adenosine triphosphate (ATP), oxygen, and magnesium. This results in the light we see from the insects.
Jellyfish
Jellyfish species such as Atolla jellyfish have rings of bioluminescent cells around their bodies. Usually, these cells flash to put off predators or attract males. Previous studies reveal that glowing jellyfish have Pulmo marinus slime that helps produce light. It is said that the jellyfish slime produces light even when rubbed on a walking stick.
Glowing Sea Turtles
Recently, some species of sea turtles, such as the hawksbill turtle, have been observed to glow. They emit neon greens and reds under ultraviolet light. Scientists attribute this to biofluorescence (probably).
Railroad Worms
With an appearance almost similar to that of a caterpillar, railroad worms are sometimes mistaken for apple maggots. However, their most prominent trait is their bioluminescence capabilities. Railroad worms have 11 pairs of luminescent organs. They start from their second thoracic segment all the way to the 9th.
Railroad worms get their name because their glowing spots resemble the windows of illuminated train cars at night.
Sea Snail
Although bioluminescence is uncommon in sea snail species, some, such as Hinea brasiliana and Phuphania, have it. The Hinea brasiliana has a shell that scatters green light everywhere. This makes it appear bigger than it actually is.
Phuphania species, on the other hand, can emit a greenish glow from the light-emitting cells found in its foot and mantle. Bioluminescence is one of the communication methods for most open-water mollusks. However, the trait is rare in marine snails living in the deep ends.
Flying Squirrel
As far as rodents go, flying squirrels are already special. Coupling that with the fact that their fur glows a brilliant, bubble-gum pink under UV light makes them exceptional. Simply put, flying squirrels are among the few mammals with fluoresce features. This means their fur can absorb light in one color and reflect it in another.
Click Beetle
Click beetles, sometimes called fire beetles or scientifically as pyrophorus, are glowing insects mostly found in tropical, subtropical, and temperate America. Their bioluminescence trait is similar to that of fireflies. The only telling difference is that click beetles don’t flash; their glows are consistent.
