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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.

Ecology:

G. polygramma is a planktonic species commonly found in neritic and oceanic waters (Steidinger and Tangen, 1996). This cosmopolitan species is a red tide bloom former associated with shellfish and fish kills. Deadly G. polygramma red tides have been reported from Florida (Steidinger, 1968), Japan (Nishikawa, 1901, Fukuyo et al., 1990, Koizumi et al., 1996), New South Wales (Hallegraeff, 1991), South Africa (Grindley and Taylor, 1964) and Hong Kong (Lam and Yip, 1990). During a bloom in Uwajima Bay, Japan, in 1994, cell levels peaked at 6.8 X 10^4 cell/ml and caused mass mortalities of cultured and natural fish and shellfish stocks (Koizumi et al., 1996).

Toxicity:

G. polygramma is a non-toxin producing species, but as a red tide species, it is associated with massive fish and invertebrate kills due to anoxia and high sulfide and ammonia levels resulting from cell decomposition (Hallegraeff, 1991, Koizumi et al., 1996).

Habitat and Locality:

G. polygramma is a cosmopolitan species common in cold temperate to tropical waters worldwide (Hallegraeff, 1991, Steidinger and Tangen, 1996).

Gonyaulax polygramma