Season 8: Bioluminescence

Previously, we've looked at the use of bioluminescence as a lure for prey, but this organism actually uses a dark part of its body with no light-emitting structures as the lure and its behavior mirrors a parasite more than a predator.

The ultimate source for many bioluminescent borrowers comes from glowing bacteria. However, while most of these relationships are beneficial for both organisms, there are examples of parasitic bioluminescent bacteria in some marine invertebrates.

Krill are some of the smallest animals and are eaten en masse by some of the largest, baleen whales. But, these crustaceans also glow and have developed methods for movement and rotation of their light-emitting structures.

Even single-celled organisms can possess bioluminescence. The effect is the result of a motion stimulus response and can be seen in breaking waves on the seashore.

Sometimes, bioluminescent organisms give us some insight into other aspects of the natural world. This is true for a sea jelly, which uses a unique set of proteins to make its glow. We have identified their structure and used their special properties to further our understanding of genetics.

Most bioluminescent organisms contain the chemical reaction inside their bodies. However, there are some that function differently. Snails and slugs leave a mucus trail behind and for a small number of species, this trail glows.

In the right hands, or in this case tentacles, bioluminescence can be a veritable swiss army knife of utility. Certain squid can use it for communication, to attract prey or mates, and even to enhance its ability to camouflage.

While anglerfish use their glow to mimic a prey item, other bioluminescent organisms take advantage of an even more instinctual type of behavior: the tendency to approach light sources. Like a moth to a flame, their prey become stuck in their traps.

Bioluminescence can also be used as a tool for communication and species identification. The placement of luminescent areas can vary by species and can be activated in different patterns. This can help animals that live in groups, such as fish, to stay together.

Bright colors are a common symbol in nature for 'danger', usually used by poisonous individuals to dissuade predators. But what about at nighttime, when most vision is monochromatic? A group of millipedes have developed a similar signal using light instead of color.