A Microbial Biorealm page on the genus Noctiluca scintillans
Eukarya; Alveolata; Dinophyceae; Noctilucales; Noctilucaceae; Noctiluca; scintillans NCBI
Description and significance
Commonly called the "Sea Sparkle", "Sea Ghost", or "Fire of the Sea", Noctiluca scintillans is a non-parasitic free-living spherical microorganism that lives in marine environments (1). It exhibits bio-luminescence when agitated through a luciferin-luciferase system in its cytoplasm. These planktonic dinoflagellates can bloom into "red tides" as a result of agricultural runoff, but have not been recorded to produce toxins.
The chromosomes of the Noctiluca scintillans are not clearly defined, unlike most other dinoflagellates with the dinokaryon which N. scintillans do not have, but are condensed through its life cycle (5). The mature cell is diploid and can show gametic meiosis, which also differs from most dinoflagellates (5). Over 100 proteins have been sequenced, and more information, especially about the proteins involved in its bio-luminescence, is currently being investigated.
Cell structure, metabolism & life cycle
It is a small and spherical cell, with diameters ranging from 0.2 to 2 mm, that lack the armor plates characteristic of most other dinoflagellates (5). While it does have a ventral groove with a flagellum present there, the cells are planktonic and not independently motile. It is a heterotrophic phagotroph whose prey consists of diatoms, other dinoflagellates, fish eggs and bacteria (3). When starved or stressed, the dinoflagellate can alter its life cycle and fuse together two vegetative cells. These planozygotes gain fat and oils, storing foood and evergy until conditions become favorable again and the dinoflagellates can emerge and function as before (4).
Ecology (including pathogenesis)
Noctiluca scintillans can be found in most marine environments throughout the world, but especially in shallow coastal areas where their photosynthetic prey are most commonly found (5). While not photosynthetic themselves, N. scintillans commonly form symbiotic relationships with photoautotrophic diatoms who live in the Eukarya's vacuoles (3).
The most unique characteristic of N. scintillans is its bio-luminescence ability due to a luciferin-luciferase reaction that occurs in thousands of "microsources", small organelles found throughout the cytoplasm that contains the molecule luciferin and the enzyme luciferase that catalyzes its oxidation (2). The light emitted can be measured accurately, and slight variations of the luciferase gene have been transgenically engineered as a visualization method in other species (1).
(1) Contag CH, Bachmann MH (2002). "Advances in in vivo bioluminescence imaging of gene expression". Annu Rev Biomed Eng 4: 235–60.
(2) [Eckert, R. and Reynolds, GT. 1967. "The Subcellular Origin of Bioluminescence in Noctiluca miliaris". J Gen Physiol. 50 (5): 1429-58
(3) [Kiørboe, T. and Titelman, J. "Feeding, prey selection and prey encounter mechanisms in the heterotrophic dinoflagellate Noctiluca scintillans." Journal of Plankton Research. 1998. V20: 8 pp. 1615-1636]
(4)  [Rapport, J. "Dinoflagellate reproduction." Dinoflagellate Habitat, Ecology, and Behavior (05 Jan. 2005).]
(5) [Umani, S. Fonda; A. Beran, S. Parlato, D. Virgilio, T. Zollet, A. De Olazabal, B. Lazzarini and M. Cabrini. 2004. "Noctiluca scintillans in the Northern Adriatic Sea: long-term dynamics, relationships with temperature and eutrophication, and role in the food web." Journal of Plankton Research. 26(5):545-561