Lingulodinium polyedrum (Stein) Dodge, 1989
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.
Cells of Lingulodinium polyedrum are angular, roughly pentagonal and polyhedral-shaped (Fig. 1). Cells range in size from 40-54 µm in length and 37-53 µm 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, Dodge, 1989, Lewis and Burton, 1988, Fukuyo et al., 1990, Steidinger and Tangen, 1996).
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 and Burton, 1988, Fukuyo et al., 1990, Steidinger and 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).
L. polyedrum reproduces asexually by binary fission. Sexual reproduction is also part of the life cycle for this species forming colorless spherical spiny cysts.
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 10^7 cells/L have been reported (Marasovic, 1989, Bruno et al., 1990).
This species forms colorless spherical spiny cysts (35-50 µm in diameter). The numerous tapering spines can reach up to 17 µm in length, all bearing spinules on their distal ends (Figs. 5,6) (Kofoid, 1911, Dodge, 1985, Dodge, 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, 1967b was discovered to be the resting spore of L. polyedrum (Wall, 1967b, 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.
Bruno et al., 1990 reported the presence of saxitoxin (PSP toxins) 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, Dodge, 1989, Steidinger and Tangen, 1996).