Gymnodinium veneficum Ballantine, 1956
Gymnodinium veneficum is an unarmoured, marine, planktonic dinoflagellate species. This small species has been associated with fish and shellfish mortality events.
Gymnodinium veneficum is an athecate species; i.e. without thecal plates. Cells are small and ovoid without dorso-ventral compression (Figs. 1-3). Cells range in size from 9-18 µm in length to 7-14 µm in width (Ballantine, 1956, Dodge, 1982, Taylor et al., 1995).
The epitheca and hypotheca are equal in size. The cell's anterior end is slightly pointed; the epitheca is without an apical groove. The hypotheca is rounded with a slight indentation at its posterior end. The deep cingulum is displaced in a descending spiral 1-2 times its width. The sigmoid sulcus slightly invades the epitheca (Figs. 1-3) (Ballantine, 1956, Dodge, 1982, Taylor et al., 1995).
Morphology and Structure:
G. veneficum is a photosynthetic species and usually has four irregularly shaped, golden-brown chloroplasts with pyrenoids; occasionally two to eight are present. The large round nucleus is centrally located (Figs. 2,3) (Ballantine, 1956, Dodge, 1982, Taylor et al., 1995).
G. veneficum reproduces asexually by binary fission; cells divide obliquely during mitosis (Ballantine, 1956).
In general cell shape and size, G. veneficum can easily be mistaken for G. micrum, a non-toxic species. However, the former species usually has four chloroplasts present and is toxic to invertebrates and fish (Taylor et al., 1995).
G. veneficum is a planktonic species first described from the English Channel (Ballantine, 1956).
G. veneficum is a known toxic species; it produces an exotoxin lethal to a wide variety of invertebrates and fish (Ballantine, 1956, Abbott and Ballantine, 1957, Dodge, 1982).
Habitat and Locality:
G. veneficum was described from the English Channel. It may be a wide-spread species, but due to its minute size, it most likely has been greatly overlooked in phytoplankton assessments (Ballantine, 1956, Dodge, 1982).