Plagiodinium

Figs 1-6. Plagiodinium belizeanum sp. nov. FIGS. 1-2. Light microscope view. Cells contain chloroplasts, spherical starch bodies (arrowheads) and a spherical posterior nucleus (n). FIG. 1. Cell is in left lateral view. FIG. 2. Cell is in right lateral view. FIGS.3-4. Cells viewed with the scanning electron microscope. FIG. 3. Cell is in left lateral view. FIG. 4. Cell is in right lateral view. Note an inclined, small, cap-shaped epitheca, deep cingulum, and an oblong hypotheca. The thecal surface is smooth. The large hypothecal plates 1'", 2'", 3'" (Fig. 3), and 4'" (Fig. 4) and antapical plate 1" are indicated. FIG. 5. The antapical 1" plate has a convex posterior shape. Small scattered thecal pores (arrowheads) are present. FIG. 6. Apical view of the epitheca. Epitheca narrowly oval pointed ventrally and rounded dorsally. The cingulum is deep, and the anterior and posterior margins are thickened. The cingulum has five plates (C1-C5) and is more depressed at its dorsal side. The hypothecal plates 1'", 2'", and 3'" are shown.

Figs 7-12. Plagiodinium belizeanum sp. nov. FIG. 7. Cell is in ventral view. Two narrow plates 1'" and 5'" are present slightly displaced. The left ventral plate (‘’’) has an anterior indentation limited to the left by a longitudinal ridge extending posteriorly, decreasing in height, and ending at the middle of the plate. The sulcus is very small. The antapical (1’’’’) plate is convexed posteriorly with a pointed tip in the center of the ventral margin. FIG. 8. Cell is in dorsal view. Hypotheca is oblong and bilaterally flattened. Plates 3'" and 4'" and antapical 1" are separated by wide intercalary bands (arrowheads). FIG. 9. Dorsal view of epitheca. The shape of the epitheca is oblong, undifferentiated (arrow), and reduced in size relative to the hypotheca. Cingulum is broad. FIG. 10. Thecal surface is smooth with scattered pores. Intercalary band delineates plates 4'" and 5'" in the form of a distinct suture. FIG. 11. Inside view of the theca. The inner cell surface is smooth; thecal plates are relatively thick with a distinct intercalary band. Dorsal plate 3'" is convex and attached to plate 4'" (arrowheads). FIG. 12. Inside view of the intercalary band. At this magnification the cell's intercalary band is broadly striated inside (arrows) and outside (arrowheads).

Figs 13-20. Line drawings of thecal plates of Plagiodinium belizeanum sp. nov. FIG. 13. Left lateral view; FIG. 14. Ventral view; FIG. 15. Antapical view; FIGS. 16. a, b) Plate composition of the epitheca and cingulum. Architecture of epithecal and cingular plates in a left view and right view; FIG. 17. Cross-section of the epitheca (a), cingulum (c), and hypotheca (h); A schematic representation of a section of a cell along the midplane parallel to the ventral surface. FIG. 18. Shape position and designation of plates. Relationship on epitheca plates is: (1’-5' and Po) cingulum (C1-C5), and sulcus (S.a.). A minute thecal element (PO), perhaps the 6th epithecal plate situated by the ventral internal border of the 4' plate, probably represents the rudiment of the PO plate. FIG. 19. Hypothecal plates (1'"-5'") and antapical plate 1"). FIG. 20. Designation, shape, and location of five sulcal plates: S.a., S.d., S.p., S.s., and S.m., surrounded by cingular plates Cl and C5 and epithecal plates 1' and 5'.

Figs 21-22. Plagiodinium belizeanum sp. nov. with flagella. FIG. 21. The longitudinal flagellum (arrowhead) and the transverse flagellum (arrow) originate within the sulcal region. The longitudinal flagellum is approximately 30 µm long and the transverse flagellum is undulate and displaced. FIG. 22. Both flagella appear to originate at close proximity to one another (arrowhead).