Species Overview: Dinophysis acuta is an armoured, marine, planktonic dinoflagellate species. It is a toxic species associated with DSP events and is commonly found in cold and temperate 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).
Thecal Plate Description: The small epitheca is made up of four plates. It is low, flat or weakly convex, and is not visible in lateral view (Balech 1976; Larsen & Moestrup 1992; Taylor et al. 1995).
Morphology and Structure: Dinophysis acuta is a photosynthetic species with yellow chloroplasts (Dodge 1982; Larsen & Moestrup 1992).
Reproduction: D. acuta 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. acuta is a planktonic oceanic and neritic species (Dodge 1982; Taylor et al. 1995; Steidinger & Tangen 1996). This is a bloom-forming species; blooms are often associated with shellfish toxicity (Taylor et al. 1995).
Toxicity: D. acuta is a toxic species that produces okadaic acid (OA), as well as Dinophysistoxin-1 (DTX1) (Lee et al. 1989; Yasumoto 1990). D. acuta has been associated with DSP outbreaks in Chile (Larsen & Moestrup 1992), Portugal (Alvito et al. 1990; Sampayo et al. 1990), Scandinavia (Dahl & Yndestad 1985; Krogh et al. 1985; Underdahl et al. 1985; Edler & Hageltorn 1990), and the USA (Freudenthal & Jijina 1985).
Species Comparison: D. acuta is very similar to D. norvegica in their general shape, and thus can easily be misidentified. D. acuta can be differentiated by its larger size and different shape: D. norvegica is widest in the middle region of the cell, whereas D. acuta is widest below the mid-section. Moreover, D. acuta has a longer left sulcal list relative to its cell length (Balech 1976; Dodge 1982; Larsen & Moestrup 1992; Taylor et al. 1995; Steidinger & Tangen 1996). D. acuta also strongly resembles a warm-water species, D. schroederi Pavillard, 1909 (Schiller 1933; Balech 1976; Burns & Mitchell 1982).
Habitat and Locality: Dinophysis acuta is widely distributed in cold and temperate waters world-wide (Larsen & Moestrup 1992; Steidinger & Tangen 1996).
Remarks: Many authors consider Phalacroma to be synonymous with Dinophysis (Steidinger & Tangen 1996).