Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921
Species Overview:
Noctiluca scintillans is an unarmoured, marine planktonic dinoflagellate species. This large and distinctive bloom-forming species has been associated with fish and marine invertebrate mortality events.
Taxonomic Description:
Noctiluca scintillans is a distinctively shaped athecate species in which the cell is not divided into epitheca and hypotheca. Cells are very large, inflated (balloon-like) and subspherical (Figs. 1-4). The ventral groove is deep and wide, and houses a flagellum, a tooth and a tentacle (Figs. 1,2,4). Only one flagellum is present in this species and is equivalent to the transverse flagellum in other dinoflagellates (Fig. 1). The tooth is a specialized extension of the cell wall (Fig. 4). The prominent tentacle is striated and extends posteriorly (Fig. 4). Cells have a wide range in size: from 200-2000 µm in diameter (Zingmark, 1970, Dodge, 1973, Dodge, 1982, Lucas, 1982, Fukuyo et al., 1990, Hallegraeff, 1991, Taylor et al., 1995, Steidinger and Tangen, 1996).
Morphology and Structure:
Noctiluca scintillans is a nonphotosynthetic heterotrophic and phagotrophic dinoflagellate species; chloroplasts are absent and the cytoplasm is mostly colorless (Figs. 1,2). The presence of photosynthetic symbionts can cause the cytoplasm to appear pink or green in color (Sweeney, 1978). A number of food vacuoles are present within the cytoplasm. A large eukaryotic nucleus is located near the ventral groove with cytoplasmic strands extending from it to the edge of the cell (Fig. 2) (Zingmark, 1970, Dodge, 1982, Fukuyo et al., 1990, Hallegraeff, 1991, Steidinger and Tangen, 1996).
Reproduction:
Noctiluca scintillans reproduces asexually by binary fission (Fig. 3) and also sexually via formation of isogametes. This species has a diplontic life cycle: the vegetative cell is diploid while the gametes are haploid. The gametes are gymnodinioid with dinokaryotic nuclei (Zingmark, 1970).
Remarks:
This species is frequently referred to as Noctiluca miliaris, although Macartney's specific name has priority. Taylor, 1976 suggested the simplest solution to the problem of nomenclature is to accept the priority of the 'scintillans'' especially as this has been used by two major works (Kofoid and Swezy, 1921, Lebour, 1925).