by Piter Kehoma Boll
If you live near the sea or visit it often, you may sometimes have seen the waves glowing while breaking on the shore at night. This beautiful phenomenon is caused by the presence of bioluminescent microorganisms, the most famous of which is our newest Friday Fellow. Scientifically known as Noctiluca scintillans, it is populary known as the sea sparkle.
The sea sparkle is a dinoflagellate and is common worlwide. It is an heterotrophic flagellate and feeds on many other small organisms, such as bacteria, diatoms, other dinoflagellates and even eggs of copepods and fish. Having only a small tentacle and a rudimentar flagellum, the sea sparkle is unable to swim, making it a very unusual predator. Studies have suggested that it preys by bumping into the prey during water flow or by ascending or descending in the water column due to density differences. It can also produce a string of mucus attached to the tentacle that entagles prey and brings them to their horrible end.
In temperate waters, the sea sparkle is an exclusive predator, but in tropical water it may maintain some of the ingested algae alive and use them in a symbiotic association to receive nutrients from photosynthesis. Diatoms of the genus Thalassiosira appear to be one of its favorites.
The most striking feature of the sea sparkle, however, is its bioluminescence, from which it receives its names. The light that it emits is produced by a chemical reaction between a compound called luciferin and an enzyme, called luciferase, that oxidizes it, causing it to emit light. The phenomenon is clearly visible on the sea during blooms of the dinoflagellate, which usually happen right after a bloom of its food.
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Kiørbe, T.; Titelman, J. (1998) Feeding, prey selection and prey encounter mechanisms in the heterotrophic dinoflagellate Noctiluca scintillans. Journal of Plankton Research 20(8): 1615–1636.
Quevedo, M.; Gonzalez-Quiros, R.; Anadon, R. (1999) Evidence of heavy predation by Noctiluca scintillans on Acartia clausi (Copepoda) eggs of the central Cantabrian coast (NW Spain). Oceanologica Acta 22(1): 127–131.
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