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Coolia tropicalis Faust, 1995

Species Overview:

Coolia tropicalis is an armoured, marine, benthic dinoflagellate species. This species was discovered in lagoonal waters from the barrier reef of Belize, Central America.

Taxonomic Description:

Species in this genus are anterio-posteriorly compressed and are observed in apical or antapical view. A distinguishing feature is the shape and size of the apical pore plate (Po) (Faust, 1992).

Cells of Coolia tropicalis are round with a nearly oblique axis (Figs. 1,2). The rounded epitheca is slightly smaller than the rounded hypotheca. The thecal surface is covered with well defined plates delineated by intercalary bands (Fig. 3). The thecal surface is smooth and covered with scattered pores (Figs. 1-5). These pores are large and round (average diameter 0.43 µm) and few in number (Fig. 5). Cells range in size from 23 to 40 µm long, 25 to 39 µm wide and 35 to 65 µm in dorso-ventral depth (Faust, 1995).

Thecal Plate Description:

The plate formula of Coolia tropicalis is: Po, 3', 7'', 7c, 8s?, 5''', 2''''. The apical pore plate (Po) is situated on apical plate 2' (Fig. 5), and positioned off-center on the epitheca. It is narrow, about 7 µm long, and has a long, slit-like opening with smooth edges (Fig. 5). Evenly spaced round pores border the slit-like opening (Figs. 1,4,5) (Faust, 1995).

The first apical plate (1') is a large pie-shaped plate positioned in the center of the epitheca (Figs. 2, 6). In ventral view, plate 1' is very wide, situated adjacent to the elongated and narrow precingular plates 1'' and 7'' (Figs. 2,6) (Faust, 1995).

The lipped cingulum is equatorial, deep, and enclosed by lists with a smooth edges (Figs. 1,2,4). Inside the cingulum a row of equally spaced pores are present. The sulcus is deep and does not reach the antapex of the cell (Fig. 2). Two wide, flexible lists partially cover the sulcus on two sides, and a narrower list is located on the antapical side (Fig. 2). The longitudinal flagellum is short. The transverse flagellum is long and often misplaced in fixed cells (Faust, 1995).

Morphology and Structure:

Cells of C. tropicalis are photosynthetic with golden-brown colored chloroplasts (Faust, 1995).


Coolia tropicalis reproduces asexually by binary fission.

Species Comparison:

Coolia tropicalis and C. monotis, although appear similar, have a number of morphological differences: 1.) 1' plate in C. tropicalis is large and pie-shaped, whereas in C. monotis it is narrow and oblong; 2.) Po plate of C. tropicalis is shorter (7 µm) than in C. monotis (12 µm); 3.) apical plate 3' in C. tropicalis is quadrangular, while it is pentagonal in C. monotis; 4.) cells of C. tropicalis are smaller than those reported for C. monotis; and 5.) thecal pores of C. tropicalis are larger and fewer in number compared to C. monotis (Balech, 1956, Besada et al., 1982, Faust, 1992, Faust, 1995, Fukuyo, 1981).


C. tropicalis is a benthic and epiphytic species frequently associated with sand and coral rubble in tropical coastal regions (Faust, 1995).


Toxicity of this species is not known.

Habitat and Locality:

Populations of Coolia tropicalis were collected from four geographical regions and three habitats. 1.) Sand-dwelling populations were collected from colored sand at South Water Cay, Belize, and benthic populations were obtained from plastic screens at Carrie Bow Cay, Belize (Caribbean Sea). 2.) Cells were also collected from a tide pool at Star Beach, and as an epiphyte from Pedina sp. at Shiira River, Iriomote Island, Japan (East China Sea). 3.) Cells were observed on Dictyota at Laurel Reef, Puerto Rico (Caribbean Sea) and 4.) at Reunion Island, France (SW Pacific Ocean). This species was a significant component of sand in lagoonal waters at South Water Cay, Belize (Faust, 1995).

Coolia tropicalis