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Prorocentrum maculosum Faust, 1993b

Species Overview:

Prorocentrum maculosum is an armoured, marine, benthic dinoflagellate species. This toxic species is often associated with floating detritus in tropical coastal regions of the Caribbean Sea.

Taxonomic Description:

Prorocentrum maculosum is a bivalvate species often observed in valve view. Cells are 40-50 µm long and 30-40 µm wide, broadly ovate with the maximum width behind the middle region, and narrow at the anterior end (Figs. 1,2). The thecal surface is rugose with distinct scattered valve poroids (85-90 per valve) (Figs. 1,2). The poroids vary from kidney-shaped to circular or oblong, and average 0.6 µm in diameter (Figs. 1-3). Spacing between poroids is 2-4 µm. The valve center is devoid of poroids (Figs. 1,2,5) (Faust, 1993b).

The valve margins of P. maculosum form a distinct ridge which appears as a flange around the cell (Fig. 4). It has equally spaced marginal pores (65-75 per valve) that appear to be larger than the valve poroids and more uniform in size (Fig. 1). The marginal pores appear as circular depressions with raised edges, pierced by much smaller pores (Figs. 5,6) (Faust, 1993b).

The periflagellar area is a broad triangle on the anterior end of the right valve (Fig. 1) made up of 8 platelets and 2 pores (Figs. 5,6). A thin apical ridge (raised margin) on the left valve surrounds the periflagellar area (Figs. 2,5). The flagellar (F) and auxiliary pores (A) are about equal in size, both surrounded by a curved and flared periflagellar collar (Figs. 5,6) (Faust, 1993b).

Morphology and Structure:

Prorocentrum maculosum is a photosynthetic species containing golden-brown chloroplasts and a centrally located pyrenoid. A large posterior nucleus is situated adjacent to the pyrenoid (Fig. 8) (Faust, 1993b).

Reproduction:

Prorocentrum maculosum reproduces asexually by binary fission.

Species Comparison:

The use of scanning electron microscopy has revealed major differences in the micromorphology of benthic species within the genus Prorocentrum (Faust, 1990a, Faust, 1993b). Under LM P. maculosum may be confused with P. lima (Faust, 1991) which has round valve pores and a smooth thecal surface. Dodge (1975), when revising the taxonomy of the genus Prorocentrum, described P. lima to be a morphologically variable species. However, the architecture of the flagellar pore area was not considered.

P. maculosum and P. lima can be distinguished by a number of surface features. In P. maculosum the thecal surface is rugose, covered with large and kidney-shaped poroids, and the periflagellar collar surrounds round, equally-sized flagellar and auxiliary pores (Faust, 1993b). In P. lima the thecal pores are round and the thecal surface smooth, the flagellar pore is larger than the auxiliary pore and surrounded by a curved periflagellar collar (Faust, 1991).

The valve margins of P. tropicalis form a distinct ridge that appears as a flange around the cell (Figs. 3,7). This is also observed for P. maculosum (Faust, 1993b).

The periflagellar architecture of P. maculosum is similar to P. hoffmannianum (Faust, 1990b), P. compressum (Abè, 1967, Dodge, 1975), P. playfairi and P. foveolata (Croome and Tyler, 1987).

Ecology:

P. maculosum is a benthic species. Cells are motile or attach to detritus or sediment by mucous strands (Faust, 1993b).

Toxicity:

This is a known toxic species that produces prorocentrolide B, a fast-acting toxin (Hu et al., 1996. Okadaic acid (OA) has also been reported from one Caribbean clone previously identified as P. concavum (Dickey et al., 1990), but reassigned to P. maculosum (Faust, 1996b, Zhou and Fritz, 1996).

Habitat and Locality:

Populations of P. maculosum are often associated with floating detritus in tropical coastal regions of the Caribbean Sea (Faust, 1993b).

Prorocentrum maculosum