In the mysterious depths of the sea as on land there lurk certain creatures whose beauty will leave you spellbound. The physical manifestation of this beauty is in the form of brilliantly gleaming lights that can illuminate entire sea beds and water surface. This phenomenon is called Bioluminescence, an intriguing biochemical process that causes living organisms, both terrestrial and aquatic, to produce and emit light of varying colors.

Below is a list of the 10 most enthralling specimens of bioluminescent organisms, that reside in this world.

1) Dinoflagellates

Believed to be amongst the oldest of surviving eukaryotes, Dinoflagellata is a phylum consisting of nearly 2,294 species of protists, both fresh water and marine. Although generally regarded as phytoplankton, i.e. photosynthetic, some Dinoflagellates are actually mixotrophic( utilizing multiple sources of energy), while still others are heterotrophic, as in deriving nutrition via the ingestion of prey. Over 18 different species of these marine flagellates exhibit bioluminescence, the most popular one being Noctiluca scintillans, also called Sea Sparkle. The greenish blue light that these organisms emanate, as a way of self-defense, is actually the work of luciferin-luciferase enzyme reaction, occurring in cytoplasmic organelles called scintillons. This usually takes places when the plankton feel threatened, as a result of disturbances on the water surface, caused either by waves or human activities. Such sights are quite common on the coasts of Puerto Rico.

Another phenomenon that dinoflagellates are associated with is Red tide, a form of toxic algal bloom that turns the affected water body into a dazzling red pool.

2) Glow worms

The term “glow worm” actually refers to a collection of different types of insect larvae and also larviform females, whose tails emit a kind of greenish-yellow light. Apart from the two genera Arachnocampa and Orfelia that are considered to be flies, all the other species are in fact beetles. While the females of the group employ bioluminescence in order to find suitable mates, the larvae of genus Lampyridae use it as a defense tactic, to ward off predators. These nocturnal invertebrates are omnivorous, with some species utilizing their glow to attract smaller prey, such as snails, midges and so on. Interestingly, the rail-road worm of Phengodidae family  possesses an extra light in the form of a bright red glow on its head. It is intriguing to note that, with the exception of North and South America, the common glow-worm is found all over the world, even in the Arctic circle.

An enormous community of glow worms actually exists inside the spectacular Waitomo Caves of New Zealand. Here, the brilliant gleam of thousands of Arachnocampa luminosa, coupled with hundreds of sticky threads that hang from the ceiling to trap flying insects, indeed make for a breathtaking picture.

3) Bioluminescent mushrooms

Glow-in-the-dark mushrooms seem a bit bizarre, doesn’t it? But the truth is, that around 71 species of mushroom-forming fungi, belonging to the Omphalotus, Armillaria and Mycenoid groups, are bioluminescent. The bluish green light they emit has a wavelength of 520-530 nm, and takes place as a result of luciferin-luciferase interaction. Found in plenty in North America, Eurasia and Australia, Panellus stipticus or the bitter oyster, is a well-known example, whose luminosity occurs mainly in the lamella. There are numerous historical references to “Foxfire”, which is in fact the name given to the striking incandescence exhibited by fluorescent fungi.

The light is generally believed to attract arthropods and other insects to facilitate spore dispersal, needed for reproduction. Additionally, it acts as warning signal to predatory animals, as it is indicative of its underlying toxicity. Interestingly, mushrooms are also hosts to a type of bioluminescent insect called fungus gnat.

4) Luminous Bacteria

Bioluminescence is also present in the microbe world, mainly amongst bacteria. The different species of luminous bacteria can be divided into three general groups: Photobacterium and Vibrio for all types of fluorescent marine bacteria, while Photorabdus contains the terrestrial counterparts. All such bacteria possess the lux operon, a set of specialized genes that are required for the production of light. Bacterial luminescence is caused by a complex enzymatic process involving luciferase.

Certain species of symbiotic bacteria are also responsible for bioluminescence in host organisms. Examples include the antenna-like organ called esca of the scary female anglerfish, that  glows brightly as a result of the bacteria living around it. The Bobtail Squid is another organism, whose bioluminescence can be attributed to a bacterium ( in this case, Vibrio fischeri) that resides inside it.

5) Fireflies

Fireflies, also known as lightning bugs, include over 2000 species of beetles, of the Lampyridae family. Seen mainly in tropical and temperate climates, this populous group of fascinating insects indeed has a few rather ‘strange’ characteristics. In some species, the female is flightless. The larvae of fireflies are also luminescent, radiating light in response to mechanical disturbance. Cannibalism has also been observed among certain species, especially in the genus Photuris.

The light is emitted from around the lower abdomen and is usually green, yellow or reddish in color. It is caused by luciferin-luciferase enzyme interaction, similar to the kind  occurring in Dinoflagellates. It is primarily used to attract mates. The light of the firefly is “cold light”, as it is devoid of any infrared and ultraviolet frequencies. Bioluminescence in fireflies is actually regarded as one of the most efficient forms of illumination, with 100% of the energy being converted to light.