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Prorocentrum emarginatum Fukuyo, 1981

Species Overview:

Prorocentrum emarginatum is an armoured, marine, benthic dinoflagellate. This species is associated with sediments, coral reefs and floating detritus in warm temperate to tropical waters.

Taxonomic Description:

Prorocentrum emarginatum is a bivalvate species often observed in valve view. Cells are broadly ovate to rotundate, slightly tapered apically, and 35-40 µm long (Figs. 1,2). Both valves are concave in the center. The anterior end of the cell is deeply indented (Fig. 3). The periflagellar area on the right valve is a deep and narrow V-shaped, distally angled depression, 10 µm long (Fig. 4). This region houses an angled periflagellar plate: a large rectangular plate (2 X 7 µm) (referred to as a 'spine' by Fukuyo, 1981). The left valve is widely excavated and curved along the apical margin (Figs. 3,4). The intercalary band is broad, transversely striated and sinuous (Figs. 2-4) (Faust, 1990b).

Both valves exhibit 2 different size pores: small (0.1 µm diameter) and large (0.2 µm diameter) (Fig. 4). The pores are uniformly round in shape with smooth margins. The larger pores, approximately 200 per valve, are arranged in radial rows, and spaced around the valve periphery (Figs. 5,6). The small valve pores are unevenly distributed and are seen only at high magnifications of well preserved specimens. The cell center is devoid of pores (Faust, 1990b). Young cells have smooth valves, but older ones can have poroids (Steidinger and Tangen, 1996).

Morphology and Structure:

Prorocentrum emarginatum is a photosynthetic species with a posteriorly located nucleus.

Reproduction:

Prorocentrum emarginatum reproduces asexually by binary fission.

Species Comparisons:

Cells of P. emarginatum resemble P. lima and P. concavum in profile, but are distinguished by the wider and deeper indentation of the periflagellar region, and by the presence of an angled rectangular periflagellar plate (Fukuyo, 1981). P. emarginatum and P. mexicanum both have radially arranged valve pores and display two different size pores (Loeblich et al., 1979, Fukuyo, 1981, Steidinger, 1983, Faust, 1990b). In addition, the intercalary band is transversely striated in these two species (Faust, 1990b).

Only two Prorocentrum species are known with a periflagellar area that is a narrow, V-shaped, distally curved depression: P. sculptile (Faust, 1994) and P. emarginatum (Faust, 1990b). Both species have a deep excavated apical area on the right valve. However, these species differ in that P. sculptile has a thin, inclined periflagellar plate, whereas P. emarginatum has a larger, rigid, rectangular plate (Faust, 1990b). Other differences include: valve surface of P. sculptile has round to oval shallow depressions evenly distributed (Faust, 1994), whereas the valve surface of P. emarginatum is smooth and round, and pores lie in radially arranged rows (Fukuyo, 1981, Faust, 1990b); P. sculptile is smaller (30-37 µm) (Faust, 1994) than P. emarginatum (35-40 µm) (Fukuyo, 1981, Faust, 1990b); and the intercalary band is smooth in P. sculptile (Faust, 1994), but transversely striated and sinuous in P. emarginatum (Faust, 1990b). P. sculptile has a pyrenoid (Faust, 1994), but P. emarginatum (Faust, 1990b) does not.

Ecology:

P. emarginatum is a benthic and epiphytic species that can be tycoplanktonic (Steidinger and Tangen, 1996). Cells swim freely or attach to substrates with mucus strands (Faust, 1990b).

Toxicity:

This species is not known to be toxic.

Habitat and Locality:

Though not common, Prorocentrum emarginatum can be found in warm temperate to tropical waters (Steidinger and Tangen, 1996) associated with sediments, coral reefs and floating detritus, and attached to macroalgae (Faust, 1990b).

Prorocentrum emarginatum