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Noctiluca miliaris

One of the largest of the single-celled animals, the noctiluna averages 1/50 to 1/25 inches across, and can be as large as 1/8 inches.

noctiluca magnified 130 times
colony of noctiluca

The noctiluca is roughly spherical in shape, with an "indenture" on the side that floats uppermost. Projecting from the "indenture side" is a flattened and cross-striated tentacle that is almost as long as the body is wide. Prey (planktonic organisms) is caught on the sticky surface of the tentacle and brought to a rod-like thickening of the surface layer that operates much like a mouth. The nucleus lies just beneath the mouth, and from it stretch thread ofcytoplasm that branch and rejoin at intervals and in which droplets and other particles are carried. The cytoplasm may be colorless, blue-green, or tinged with yellow, and between the strands is a semi-fluid sap. Undigested particles are eventually discharged through the mouth.

this noctiluca has just ingested a brittle star larva, magnified 200 times
noctiluca that has ingested a brittle star larva

Noctiluca does not swim actively, but the constant waving of its tentacle (at a rate of about half a dozen times a minute) does tend to move the animal about.

Noctiluca usually reproduces by splitting in two (asexual reproduction), a process that takes 12 to 24 hours. Although it is known that noticulates do occasionally produce gametes that in turn come together to form new noticulates (sexual reproduction), how those gametes come together and what happens afterward has never been determined.

Noctiluca occurs in warm and temperate shallow coastal waters and at times the numbers floating near the surface may be enough to turn the sea into "soup." That "soup" can sometimes be seen at night as an almost ghostly glow. That glow is the result of a specific type of granule in the noctilucates' cytoplasm that gives out a brief flash of light when the animals are disturbed.

a research vessel sails through a swarm of noctiluca
noctiluca soup


Maurice Burton and Robert Burton (editors) Funk & Wagnalls Wildlife Encyclopedia New York, New York: Funk & Wagnalls, Inc., 1974

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The Robinson Library >> Phylum Protoza

This page was last updated on 09/03/2018.