Alexandrium pseudogonyaulax

A. pseudogonyaulax is a producer of goniodomin A

A. pseudogonyaulax is photosynthetic with central chloroplasts.

A. pseudogonyaulax is a medium sized cell which is dorso-ventrally flattened. The 1? plate is characteristically displaced and very short, almost pentagonal in outline. The ventral pore is semicircular in shape. The 1? plate is not in contact with the Po. The apical pore plate is oval shaped with a large comma shaped foramen and several irregular pores The cingulum is only weekly excavated. It is descending. Displacement is less than its width. The sulcus is not bordered by lists. The sa invades the epitheca slightly on the righthand side. It fits into a nothch formed by the 6? and 1? plates.

A. pseudogonyaulax is a medium-sized cell. Cells are wider than long. The 1? plate is characteristically displaced and very short, almost pentagonal in outline.

A. pseudogonyaulax is a coastal and brackish water dinoflagellate species. Blooms of this species are commonly reported in the Strait of Georgia, British Columbia (North Pacific Ocean) (Taylor & Haigh 1993).
This species produces a characteristic and unusual resting cyst: a non-smooth cyst. The cysts are round and dark, and are often covered with a mucilaginous layer (Fig. 8). They contain a reddish-orange accumulation body. Size ranges from 40 to 55 µm in diameter. The cyst wall consists of two layers: a smooth inner layer and a paratabular outer layer (Fig. 9). The cyst paratabulation equals the tabulation of a vegetative cell. This is the only reported species in the genus Alexandrium to produce a non-smooth cyst (Montresor et al. 1993; Nichetto et al. 1995).

A. pseudogonyaulax is a coastal species which has been reported from several localities in Europe: France along the Mediterranean coast (Biecheler 1952), Italy in the Gulf of Trieste, North Adriatic Sea (Honsell et al. 1992; Montresor et al. 1993; Nichetto et al. 1995), Portugal and Norwegian fjords (Balech 1995). In the Pacific Ocean this species is a common bloom former in the Gulf of Georgia in British Columbia (Taylor & Haigh 1993), and populations have been observed in coastal waters of Japan (Inoue, in Kita & Fukuyo 1988).

A. pseudogonyaulax is a photosynthetic species with central radiating yellow-brown chloroplasts. The transversely elongated nucleus is large and curved, and centrally located (Balech 1995; Montresor 1995).

Holotype: Goniodoma pseudogoniaulax Biecheler, 1952: 55, figs. XXX-XXXII
Type Locality: Mediterranean Sea: Thau Lagoon, France

A. pseudogonyaulax reproduces asexually by binary fission. This species also has a sexual cycle with isogamous mating types. The smaller rounder gametes (Fig. 7) fuse (one gamete engulfs the other), produce a planozygote which then encysts into a characteristic resting cyst (Fig. 8)(Montresor et al. 1993; Montresor 1995).

A. pseudogonyaulax closely resembles two other Alexandrium species: A. hiranoi and A. satoanum. Common features include general shape and size, and lack of contact of the first apical plate, 1', with the Po. Distinguishing features lie in the cell outline, the ventral pore, the 1' plate, cyst morphology and habitat: a) A. hiranoi has a round shape, A. pseudogonyaulax is wider than long, A. satoanum is also wider than long with the general outline resembling a top: the epitheca and hypotheca have straighter sides; b) the ventral pore of A. hiranoi is circular and invades the 4' plate, in A. pseudogonyaulax the ventral pore is semi-circular and does not invade the 4', and in A. satoanum, no ventral pore is present (has a.a.p. and p.a.p); c) the 1' plate in A. hiranoi is slender and rectangular, whereas in A. pseudogonyaulax the 1' is almost pentagonal; d) the cyst of A. hiranoi is smooth, while the cyst of A. pseudogonyaulax is paratabulate with thick sutures; and e) A. hiranoi is found in rockpools, A. pseudogonyaulax is found in coastal brackish habitats (Kita & Fukuyo 1988; Montresor et al. 1993; Steidinger & Tangen 1996). This species roughly resembles A. tamarense, however the latter species is not as round, and has a broader APC (Taylor et al. 1995).

Alexandrium pseudogonyaulax is an armoured, marine, planktonic dinoflagellate. It is a toxic species found in coastal regions and brackish environments.

Goniodoma pseudogoniaulax Biecheler, 1952
Alexandrium pseudogonyaulax (Biecheler) Horiguchi, 1983

A. pseudogonyaulax cells are medium to large, irregularly pentagonal-shaped with moderate dorso-ventral flattening. Cells are wider than long; the epitheca is slightly shorter than the hypotheca (Figs. 1, 2). The first apical plate (1') is characteristically displaced with a large ventral pore on the anterior margin (Figs. 3-5). The thecal plates are smooth and thin with scattered minute pores. Cells range in size between 34-60 µm in length and 39-69 µm in width (Balech 1995; Montresor et al. 1993; Steidinger & Tangen 1996).

The plate formula for A. pseudogonyaulax is: Po, 4', 6'', 6c, 10s, 5''', 2''''. The apical pore plate (Po) is oval shaped, contains a large comma-shaped foramen and a number of irregular pores, and is positioned longitudinally on the apex (Figs. 3, 4, 6). The distintive 1' plate does not come in contact with the Po (Figs. 3, 4, 6); it is roughly pentagonal and wider anteriorly (Figs. 3, 6). The sloped anterior margin bears a large ventral pore that is wider than long (Figs. 3, 4, 6). The ventral pore does not penetrate the 4' plate (Balech 1995; Montresor et al. 1993; Yuki & Fukuyo 1992).
The short, convex epitheca is dome-shaped (Figs. 1, 2). The hypotheca is slightly longer with an obliquely concave antapex (Figs. 1, 2). The shallow cingulum is displaced in a descending fashion less than one times its width (Fig. 5). The sulcus lacks lateral lists. It slightly penetrates the epitheca obliquely on the right (Balech 1995).

A. pseudogonyaulax produces a unique phycotoxin, goniodomin A (GA) that has an antifungal effect (Murakami et al. 1988). The toxin GA targets the liver and thymus (Terao et al. 1989; 1990).