Gymnodinium veneficum Ballantine, 1956
Species Overview:
Gymnodinium veneficum is an unarmoured, marine, planktonic dinoflagellate species. This small species has been associated with fish and shellfish mortality events.
Taxonomic Description:
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).
Reproduction:
G. veneficum reproduces asexually by binary fission; cells divide obliquely during mitosis (Ballantine, 1956).
Species Comparison:
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).