Diversity of Bioluminescent Organisms

Living beings that glow in the dark

I imagine that some people may not be familiar with the image above, but I assure you that these lights were not added through image editing.

These lights are naturally produced by dinoflagellate species such as Noctiluca scintillans (protist), microscopic organisms that constitute a part of marine plankton.

The first time I saw them was in Chacahua Lagoon, Oaxaca, Mexico, but actually, they can be seen on various beaches around the world.

Walking on the beach at night or sailing in a dark sea, you will be able to see these bright lights on the water at specific seasons of the year [check out this video].

Production of light by living organisms

Bioluminescence is the capability of some organisms to emit visible light as a result of a chemical reaction [1].

Some species can not produce their own light per se, but can be bioluminescent if they have symbiotic relationships with bacteria that allow them to glow in the dark.

The luminescent reaction in most organisms occurs through an enzymatic oxidation reaction involving two substances: luciferin (a protein that produces light when oxidized) and luciferase (an enzyme that catalyzes the biochemical reaction in the presence of oxygen) [2].

Organisms such as fireflies (insects of the family Lampyridae) can carry out this chemical reaction inside of specialized light-emitting organs located in the lower part of their abdomen.

Evolution of bioluminescent organisms

Despite there being relatively few known luminous species, bioluminescence is a widely distributed feature in nature (it can be found in ~666 genera from 13 phyla) [3,4].

Bioluminescence evolved as an active form of communication for various purposes, such as hunting prey, warding off predators, and attracting mates [5].

It is more frequent in marine organisms such as fishes, cnidarians, ctenophores, crustaceans, mollusks, echinoderms, chaetognaths, annelids, and protists, but it also can also be found in some groups of bacteria, fungi, myriapods, and insects.

There are many chemically different luciferins and luciferases isolated from luminous organisms in different phylogenetic groups.

While light-emitting systems of not-related biological groups share some similarities, they can be functionally and biochemically very different [2,6].

Indeed, genes and proteins involved in bioluminescence in different biological groups of organisms are mostly unrelated.

This molecular biodiversity means that then each of them must have evolved independently from a different origin. In evolutionary biology, this event is better known as convergent evolution.

Indeed, it is estimated that the ability to emit light has arisen independently at least 30 times in the course of evolution, and there is no discernible evolutionary pattern across different taxa [2,7].

A curious fact is that Charles Darwin was puzzled by the evolution of bioluminescence.

He couldn’t imagine how small changes (phyletic gradualism), could lead, apparently out of the blue, to a completely new phenomenon (such as specialized light-producing organs), through his idea of natural selection [6].

Currently, bioluminescent organisms are a target for different scientific research.

There are over 30 known bioluminescent systems, but only 11 systems have been characterized [8].

Genes responsible for the bioluminescence reaction are frequently used for molecular markers or reporter genes that have different biotechnological applications.

Bioluminescence is currently used for gene assays, the detection of protein–protein interactions, high-throughput screening (HTS) in drug discovery, hygiene control, analysis of pollution in ecosystems, and in vivo imaging in small mammals [8].

You can find more information about bioluminescent organisms in the following links: [1,2,3,4,5,6,7,8,9,10,11].

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