Noctiluca Scintillans, Gippsland Lakes, Vistoria, Australia

The size of the single-celled N. scintillans ranges from 200 to 2,000 µm in diameter, assuming the generally spherical shape. N. scintillans lacks the armor plates possessed by other types of dinoflagellates. And, unlike many other dinoflagellates, the chromosomes of the Noctiluca are not clearly-visible and condensed throughout its lifecycle.
Anatomy
N. scintillans has a ventral groove within which is located a flagellum, an extension of the cell wall called a tooth, and a striated tentacle involved in ingestion that projects posteriorly. The flagellum does not move the organism and therefore the non-motile N. scintillans depends upon regulation of its buoyancy within the water column – perhaps by controlling its cellular concentration of ions and ammonia.