Coolia monotis

Coolia monotis is the cosmopolitan type species of the dinoflagellate genus Coolia.

Coolia monotis is suspected to be a cryptic species because of the considerable morphological and genetic diversity (Penna et al. 2005, Dolapsakis et al. 2006).

Coolia monotis is a planktonic, benthic and epiphytic species (Faust 1992; Steidinger & Tangen 1996). This toxic species has been identified as causing shellfish toxicity (neurotoxin poisoning-like symptoms) in oysters (Crassostrea gigas) in Rangauna Harbour, Northland, New Zealand (Rhodes & Thomas 1997).

Coolia monotis is a neritic species that is quite common world-wide in temperate to tropical waters (Steidinger & Tangen 1996). Populations have been observed from plankton samples, oyster beds, brackish habitats and tidal pools, as well as mangrove environments. This species is most common in warm shallow waters of the Caribbean and Mediterranean Seas, and the Pacific Ocean (Faust 1992).

Cells of C. monotis are photosynthetic, with many golden-brown discoid chloroplasts. Chloroplasts radiate from the center of the cell. This species has one dorsally situated nucleus located in the hypotheca. A large, round pusule is also present adjacent to the sulcus that seems to open independently into the sulcus (Faust 1992).

Holotype: Coolia monotis Meunier, 1919: plate 19, figs. 13-19
Type Locality: North Sea: Deswartes, Nieuport, Belgium

Coolia monotis reproduces asexually by binary fission. Sexual reproduction has been documented for this species: gametes fuse and a planozygote is formed (Fig. 7) (see Faust 1992).

Coolia and Ostreopsis species have morphological similarities and differences: 1.) the Po of Coolia monotis is similar in architecture, but considerably longer (12 µm) than in O. heptagona (8-9 µm) and O. ovata (6-7 µm); 2.) a ventral pore of Coolia monotis is located on the right-hand ventral margin between apical plate 1' and precingular plate 6" which is similar to the location of the ventral pore of O. ovata; and 3.) Coolia monotis has a relatively short (20 µm) longitudinal flagellum compared to other benthic dinoflagellate species, but it is significantly longer than the longitudinal flagellum of O. ovata (approximately 12 µm) (Besada et al. 1982; Faust 1992; Norris et al. 1985).
Besada et al. (1982) suggested that mucilage secretion occurred through the ventral pore from the pusule of Ostreopsis species. This may also be true for Coolia monotis cells since they attach to the bottom of culture plates by mucus threads or are entwined in a veil of mucilage. Mucus formation prompted Besada et al. (1982) to consider a relationship between Coolia monotis, O. ovata and Gambierdiscus toxicus. Coolia, Ostreopsis and Gambierdiscus also exhibit a similar internal anatomy (Besada et al. 1982) and sterol composition (Besada 1982). Gambierdiscus toxicus, however, differs in having an additional sterol compound (Loeblich & Indelicato 1986) possibly indicating a more distant relationship to the other two species.

Coolia monotis is an armoured, marine, benthic and toxic dinoflagellate species with world-wide distribution.

Glenodinium monotis (Meunier) Biecheler, 1952
Ostreopsis monotis (Meunier) Lindemann, 1928

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 monotis are compressed, round and lens-shaped; axis is oblique (Figs. 1-3). The rounded epitheca is slightly smaller than the rounded hypotheca (Fig. 1). The thecal surface is covered with well defined plates delineated by a network of intercalary bands (Figs. 1-3). Cell size ranges from 25 to 45 µm in diameter and 30 to 50 µm in length (Fukuyo 1981; Dodge 1982; Tolomio & Cavolo 1985b; Faust 1992).
The thecal surface is smooth and covered with sparsely scattered large pores with smooth edges (Figs. 1-4). Marginal pores are present on both sides of the lipped cingulum (Figs. 1, 3) (Faust 1992).

The plate formula of Coolia monotis is: Po, 3', 7'', 6c, 6s, 5''', 2'''' (Fig. 8). On the epitheca a distinct oblong apical pore plate (Po) (Fig. 5), positioned off-center, is located adjacent to apical plates 1', 2', and 3' (Figs. 2, 8). The Po is about 12 µm long, slightly curved and narrow, and bears a long slit-like apical pore (Fig. 5). Two supporting costae border the slit-like pore. Surrounding the costae and apical pore are evenly spaced round pores (Fig. 5). The large Po is easily observed under LM and is useful for identification (Faust 1992; Steidinger & Tangen 1996).
The lipped cingulum is equatorial, narrow, and enclosed by lists with a smooth edge (Figs. 1-3 ,6). A ventral pore is located on the right-hand ventral margin between apical plate 1' and precingular plate 6'' (Fig. 1). The ventral pore has an ellipsoidal shape with an average diameter of 0.5 µm (Faust 1992).
The sulcus is narrow, indented, and does not reach the antapex of the cell (Figs. 1, 6). It has a deep chamber-like appearance with straight walls. Two slightly curved, wide, flexible lists partially cover the sulcus at two sides (Figs. 1, 6) (Faust 1992).

This species is considered toxic (Nakajima et al. 1981) producing cooliatoxin, a neurotoxic analog to yessotoxin (Holmes et al. 1995, Rhodes & Thomas 1997).