Gyrodinium galatheanum (Braarud) Taylor, 1992
Species Overview:
Gyrodinium galatheanum is an unarmoured, marine, planktonic dinoflagellate species. It is a common red tide former discovered in Walvis Bay, South Africa, associated with fish kills.
Taxonomic Description:
Gyrodinium galatheanum is an athecate species; i.e. without thecal plates. Cells are small and oval to round in ventral view (Figs. 1-5). A well-defined apical groove is present ventrally on the anterior of the cell (Figs. 1,2,5). The apical groove can produce a slight indentation at the apex (Figs. 4,5). Cells range in size from 9-17 µm in length to 8-14 µm in width (Braarud, 1957, Taylor et al., 1995, Steidinger and Tangen, 1996).
The epitheca and hypotheca are both round (Figs. 1-5). The cingulum is displaced in a descending fashion up to 3 times its width (Figs. 1-5). The broad cingulum is deeply excavated and houses the transverse flagellum (Figs. 1,2,5). The narrow sulcus slightly invades the epitheca adjacent to the apical groove (Figs. 1,2,5) (Braarud, 1957, Taylor et al., 1995, Steidinger and Tangen, 1996).
Morphology and Structure:
G. galatheanum is a photosynthetic species with several rounded chloroplasts. The large nucleus is round and centrally located (Figs. 3,5). This species does not have peridinin as a major accessory pigment, but has a fucoxanthin derivative and chlorophyll c3 (Braarud, 1957, Bjornland and Tangen, 1979, Johnsen and Sakshaug, 1993, Taylor et al., 1995, Steidinger and Tangen, 1996).
Reproduction:
G. galatheanum reproduces asexually by binary fission.
Species Comparison:
In shape and size Gyrodinium galatheanum resembles two other small athecate gymnodinoids, G. veneficum and G. micrum (Taylor et al., 1995). Physiologically G. galatheanum is closely related to the toxic species Gyrodinium aureolum. Both lack peridinin while both have chlorophyll c3 , which is characteristic of several bloom-forming prymnesiophytes (Johnsen and Sakshaug, 1993).