Species Overview: Dinophysis norvegica is an armoured, marine, planktonic dinoflagellate species. This species is a bloom-forming toxic species associated with DSP events. It is commonly found in cold neritic waters.
Taxonomic Description: Species in this genus are laterally compressed with a small, cap-like epitheca and a much larger hypotheca (dorso-ventral depth of epitheca is 1/2 to 2/3 of hypotheca). The shape of the cell in lateral view is the most important criterion used for identification (Taylor et al. 1995). However, size and shape varies considerably in this species (Larsen & Moestrup 1992).
Thecal Plate Description: The small epitheca is low, flat or weakly convex, and is obscured by cingular lists. It is made up of four plates with a sinuous sculpture (Balech 1976; Dodge 1982; Taylor et al. 1995).
Morphology and Structure: Dinophysis norvegica is a photosynthetic species with yellow chloroplasts and a posteriorly oriented nucleus (Fig. 5) (Schiller 1933; Larsen & Moestrup 1992).
Reproduction: D. norvegica reproduces asexually by binary fission. Hansen (1993) speculates that sexual reproduction, with sexual dimorphism, is part of the life cycle for this species.
Ecology: D. norvegica is a planktonic neritic species (Schiller 1933; Taylor et al. 1995; Steidinger & Tangen 1996). Blooms have been reported from the British Isles (Dodge 1977), Scandinavia (Dahl & Yndestad 1985; Krogh et al. 1985) and the U.S. (Freudenthal & Jijina 1985). Cell numbers of about 80,000cells/L have been reported from Denmark (Larsen & Moestrup 1992). Jacobson & Andersen (1994) found a high number of food vacuoles in cells of Dinophysis norvegica and deduced that mixotrophy is an important aspect of its biology. They speculate that this species feeds by way of a peduncle (myzocytosis), the feeding mode used by the heterotrophic species Dinophysis rotundata and D. hastata (Schnepf & Deichgraber 1983). The peduncle passes through the cytostomal opening in the theca when the cell is feeding (Jacobson & Andersen 1994).
Toxicity: D. norvegica is a known toxin producer associated with diarrhetic shellfish poisoning (DSP) events. Cembella (1989), Lee et al. (1989) and Yasumoto (1990) reported Dinophysistoxin-1 (DTX1) and okadaic acid (OA) production from this species.
Species Comparison: Dinophysis norvegica is very similar to D. acuta in shape, and thus can easily be misidentified. Balech (1976) found that the plate patterns of these two species are very similar, but are more variable in D. norvegica. These species can be differentiated by their size (although they overlap) and deepest position: D. acuta is larger and widest below the mid-section, whereas D. norvegica is smaller and widest in the middle region of the cell (Balech 1976; Dodge 1982; Dodge 1985; Larsen & Moestrup 1992; Taylor et al. 1995; Steidinger & Tangen 1996).
Habitat and Locality: D. norvegica is widely distributed in cold, temperate northern waters (Dodge 1985; Steidinger & Tangen 1996).
Remarks: D. norvegica is considerably variable in size and shape (Schiller 1933; Balech 1976). A number of forms and varieties have been described: D. norvegica var. debilor Paulsen and D. norvegica var. crassior Paulsen, both of which were subsequently raised to species level (Paulsen 1949). Solum (1962) later considered them as different forms of D. norvegica.