Identifying Harmful Marine Dinoflagellates

Lingulodinium polyedrum
(Stein) Dodge, 1989
Plate 29, Figs. 1-6

Species Overview: Lingulodinium polyedrum is an armoured, marine, bioluminescent dinoflagellate species. This warm-water species is a red tide former that has been associated with fish and shellfish mortality events.

Taxonomic Description: Cells of Lingulodinium polyedrum are angular, roughly pentagonal and polyhedral-shaped (Fig. 1). Cells range in size from 40-54 Ám in length and 37-53 Ám in transdiameter width. No apical horn or antapical spines present (Fig. 1). Thecal plates are thick, well defined, and coarsely areolate. Distinct ridges are present along the plate sutures (Figs. 1, 2). Numerous large trichocyst pores are present within areolae (Fig. 3) (Kofoid 1911; Dodge 1985; 1989 Lewis & Burton 1988; Fukuyo et al. 1990; Steidinger & Tangen 1996).

Nomenclatural Types:
Holotype: Gonyaulax polyedra Stein, 1883: p. 13, pl. 4, figs. 7-9
Type Locality: unknown
Gonyaulax polyedra Stein, 1883
Lingulodinium machaerophorum (Deflandre and Cookson) Wall, 1967 (cyst)
Hystrichosphaeridium machaerophorum Deflandre and Cookson, 1955 (cyst)

Thecal Plate Description: The plate formula for L. polyedrum is: Po, 3', 3a, 6'', 6c, 7s, 6''', 2''''. The epitheca bears shoulders, nearly straight sides, and an off-center apex which is flattened or slightly pointed (Figs. 1, 4). The apical pore plate (Po) contains a raised inner elliptical ridge (Fig. 2). The first apical plate (1') is long and narrow, comes in direct contact with the Po, and bears a ventral pore on its right side (Figs. 1, 2, 4). The deeply excavated cingulum is nearly equatorial, and displaced one to two times its width. It is descending with narrow ribbed lists (Figs. 1, 2, 4). The deep sulcus invades the epitheca slightly and widens posteriorly. The hypotheca has straight sides and a truncated antapex (Figs. 1 2, 4) (Kofoid 1911; Dodge 1985; Dodge 1989; Lewis & Burton 1988; Fukuyo et al. 1990; Steidinger & Tangen 1996).

Morphology and Structure: L. polyedrum is a photosynthetic species with dark orange-brown chloroplasts. The unusual carotenoid, peridinin, is present in the chloroplasts. Also present is a pusule, a C-shaped nucleus, and scintillons (light-emitting organelles) (Kofoid 1911; Schmitter 1971; Jeffrey et al. 1975).

Reproduction: L. polyedrum reproduces asexually by binary fission. Sexual reproduction is also part of the life cycle of this species producing spherical spiny cysts.

Ecology: L. polyedrum is a bioluminescent planktonic species commonly found in neritic waters. It is responsible for magnificent displays of phosphorescence at night in warm coastal waters (Kofoid 1911). This warm-water species is a red tide former that has been associated with fish and shellfish mortality events. Deadly red tides have been reported from southern California (San Diego region)(Kofoid 1911; Allen 1921), as well as in the Adriatic Sea (Italy and Yugoslavia) where cell levels as high as 2 X 107 cells/L have been reported (Marasovic 1989; Bruno et al. 1990).
This species forms colorless spherical spiny cysts (35-50 Ám in diameter). The numerous tapering spines can reach up to 17 Ám in length, all bearing spinules on their distal ends (Figs. 5, 6) (Kofoid 1911; Dodge 1985; 1989; Fukuyo et al. 1990). The cyst of this species is able to fossilize (found in fossil deposits all the way back to the late Cretaceous period): the hystrichosphere (fossilized dinoflagellate cyst) Lingulodinium machaerophorum (Deflandre and Cookson) Wall, 1967 was discovered to be the resting spore of L. polyedrum (Wall 1967; Fensome et al. 1993).
Marasovic (1989) reported production of temporary resting cysts in a waning red tide dominated by L. polyedrum in the Adriatic Sea (Yugoslavia). Near the end of a bloom, the population produced temporary cysts and remained in the plankton. Once environmental conditions were favorable again, the cysts were able to re-seed the area, and thus initiate another red tide event.

Toxicity: Bruno et al. (1990) reported the presence of a paralytic shellfish poison (PSP) toxin, saxitoxin, in water samples taken during a bloom of L. polyedrum.

Habitat and Locality: L. polyedrum is a widely distributed species found in warm temperate and subtropical waters of coastal areas (Kofoid 1911; Dodge 1985; 1989; Steidinger & Tangen 1996).

Figure 1: Morphology of a Dinoflagellate