Gambierdiscus belizeanus Faust, 1995
Species Overview:
Gambierdiscus belizeanus is an armoured, marine, benthic dinoflagellate species. It 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. The epitheca and hypotheca are not noticeably different in size. A distinguishing feature is the shape and size of the apical pore complex (APC) (Faust, 1992).
Cells of Gambierdiscus belizeanus are round to ellipsoid (Figs. 1,2). Both epitheca and hypotheca are convex. The cell surface is deeply areolate; the areolae are distinguishable under light and scanning electron microscopy (Figs. 2, 4). The areolae are round to oval with a smooth edge. At times they appear hexagonal in shape (Fig. 4) with round pores (average diameter 0.22 µm) located in deep depressions (Fig. 3). Cells range in size between 53 to 67 µm long, 54 to 63 µm wide and 92 to 98 µm in dorso-ventral depth (Faust, 1995).
Thecal Plate Description:
The plate formula of Gambierdiscus belizeanus is: Po, 3', 7'', 6c, 8s, 5''', 1p, 2'''' (Faust, 1995). The APC is oriented ventrally (Fig. 3). It is comprised of an ellipsoidal apical pore plate (Po) with a characteristic large fish-hook shaped curved apical pore surrounded by rows of evenly distributed pores (Fig. 3). Apical plate 2' is the largest of the three apical plates (Fig. 1) (Faust, 1995).
The lipped cingulum consists of six deep and narrow cingular plates. It is distinct with an evenly spaced array of marginal areolae and elongated depressions, which creates the optical effect of a striated pattern (Figs. 2,5,6). The curved ends of the cingulum are located at the edge of the sulcal opening (Figs. 2, 4). The sulcus is a broad, deeply excavated opening (Fig. 4) (Faust, 1995).
The hypotheca consists of 8 plates (Fig. 2). The posterior intercalary plate (1p) is long, narrow and pentagonal-shaped, wedged between postcingular 2''' and 4''' plates. The 2'''' antapical plate is small and five-sided; it folds onto the sulcus to form a ridge (Fig. 2). The 2''' and 4''' plates are very wide, occupying 80% of the width in the hypotheca (Fig. 2) (Faust, 1995).
Morphology and Structure:
Cells of Gambierdiscus belizeanus are photosynthetic containing golden-brown chloroplasts and a posteriorly located oblong nucleus (Faust, 1995).
Reproduction:
G. belizeanus reproduces asexually by binary fission.
Species Comparisons:
Gambierdiscus belizeanus and G. toxicus share a number of similarities, yet both are distinct: 1.) epithecal plates of G. belizeanus are similar in architecture to G. toxicus, but differ in thecal surface morphology, thecal surface of the former species is areolated while that of the latter species is smooth (Adachi and Fukuyo, 1979); 2.) shape and size of antapical plate 2'''' in G. belizeanus (Fig. 2) is a narrow pentagonal-shaped plate (Faust, 1995), significantly different from that of G. toxicus which is quadrangular (Adachi and Fukuyo, 1979); and 3.) 1p plate in G. belizeanus is long and narrow, whereas the 1p plate in G. toxicus is wide (Faust, 1995).