Gonyaulax polygramma Stein, 1883
Species Overview:
Gonyaulax polygramma is an armoured, planktonic marine dinoflagellate species. It is a red tide bloom species associated with massive fish and shellfish kills.
Taxonomic Description:
Cells of Gonyaulax polygramma are medium-sized, elongate and pentagonal (Fig. 1). The tapered epitheca bears a prominent apical horn, and exceeds the symmetrical hypotheca (Figs. 1-3). Longitudinal ridges ornament the thecal surface; reticulations are present between the ridges (Figs. 1-3). On mature cells, longitudinal ridges may be thick and spinulous. Cells range in size from 29-66 µm in length and 26-56 µm in dorso-ventral depth (Dodge, 1982, Fukuyo et al., 1990, Hallegraeff, 1991, Steidinger and Tangen, 1996).
Thecal Plate Description:
The plate formula for G. polygramma is: Po, 3', 2a, 6'', 6c, 4-8s, 6''', 1'''' (Dodge, 1989). The epitheca is convex to angular, and bears 12 apical plates (Figs. 1-3). The elliptical apical pore plate (Po) does not extend onto the dorsal side of the cell. The left-handed cingulum is post-median and displaced about 1.5 times its width without overhanging (Figs. 1,2,6,7). The slightly excavated sulcus widens posteriorly; it invades the epitheca slightly (Figs. 1,2,6,7). The hypotheca is truncate with straight sides and consists of six plates; 1-3 antapical spines present (Figs. 2,3) (Dodge, 1982, Fukuyo et al., 1990, Hallegraeff, 1991, Steidinger and Tangen, 1996).
Morphology and Structure:
G. polygramma is a photosynthetic species with chloroplasts. The large nucleus is oval shaped and is located posteriorly (Dodge, 1982).
Reproduction:
G. polygramma reproduces asexually by binary fission.