Prorocentrum concavum Fukuyo, 1981
Prorocentrum concavum is an armoured, marine, benthic dinoflagellate. This toxic species is often associated with floating detritus and sediments in tropical and neritic waters.
P. concavum is a bivalvate species often observed in valve view. Cells are broadly ovoid. Valve centers are concave and flattened. Cells measure 50-55 µm in length and 38-45 µm in width. The valve surface is covered with 1000-1100 prominent shallow areolae. The areolae are round to oval with smooth edges (Fig. 1) and often observed with a central pore (0.8 µm diameter) (Fig. 3). No marginal pores are present and the cell center is devoid of areolae (Fig. 5). The intercalary band is granulated and horizontally striated (Fig. 1,2) (Fukuyo, 1981, Faust, 1990b).
The periflagellar area is a narrow, rimmed, V-shaped depression on the right valve (Figs. 1,4). It is composed of eight apical plates, without ornamentation, fitted with a large flagellar pore, and a much smaller auxiliary pore. The left valve is slightly indented anteriorly with a thickened apical ridge (raised margin) bordering the periflagellar area (Fig. 1) (Fukuyo, 1981, Faust, 1990b).
Morphology and Structure:
Prorocentrum concavum is a photosynthetic species with golden-brown chloroplasts (Faust, 1990b). Two cup-shaped pyrenoids are also present (Fukuyo, 1981).
Prorocentrum concavum reproduces asexually by binary fission.
Prorocentrum concavum, at the LM level, is difficult to differentiate from a number of other Prorocentrum species due to their similar size and shape; e.g. P. concavum is often confused with P. lima (Fukuyo, 1981, Faust, 1990b), but P. lima is not areolate and bears marginal pores (Faust, 1990b).
The location and arrangement of areolae on the surface of P. concavum closely resembles that of P. hoffmannianum (about 670/valve) (Faust, 1990b) and P. belizeanum (about 950/valve) (Faust, 1993a); however, the latter two species have fewer areolae per valve and also have marginal pores, while P. concavum does not (Faust, 1990b).
P. concavum and P. tropicalis (Faust, 1997) have similar intercalary bands: granulated and horizontally striated.
P. concavum is a benthic species that can also be tycoplanktonic. Cells can be either motile or embedded in mucus attached to detritus (Faust, 1990b, Steidinger and Tangen, 1996).
This species is known to be toxic producing the following toxins: fast-acting toxin (FAT) (Tindall et al., 1984), DSP toxins (Hu et al., 1993) including okadaic acid (OA) (Dickey et al., 1990), and an unnamed toxin (Tindall et al., 1989).
Habitat and Locality:
P. concavum populations are often associated with floating mangrove detritus and sediments in tropical and neritic waters (Faust, 1990b, Steidinger and Tangen, 1996).