Page 66 - Algae Anatomy, Biochemistry, and Biotechnology

Anatomy 49

from the euglenoid pellicle, hence with a completely different accepted meaning, and in our opinion
its use should be avoided. The layer consists primarily of cellulose, sometimes with a dinosporine
component, a complex organic polymer similar to sporopollenin that make these algae fossilizable.
In some athecate genera, such as Noctiluca sp., this layer reinforces the amphiesma, and the cells
are termed pelliculate. This layer is sometimes present beneath the amphiesma, as in Alexandrium
sp., or Scrippsiella sp., and forms the wall of temporary cysts.
According to Dodge and Crawford (1970), the amphiesma construction falls into eight reason-
ably distinct categories: (1) simple membrane underlain by a single layer of vesicles 600–800 nm
in length, rather flattened, circular, or irregular in shape, with a gap of at least 40 nm between adja-
cent vesicles that may contain dense granular material; beneath the vesicles are parallel rows of
microtubules which lie in groups of three; this simple arrangement is present in Oxyrrhis
marina; (2) simple membrane underlain by closely packed polygonal (generally hexagonal)
vesicles 0.8–1.2 mm in length, frequently containing fuzzy material; these vesicles and the cell
membrane are occasionally perforated by trichocyst pores; beneath the vesicles lie microtubules
in rows of variable number; this type of amphiesma has been found in Amphidinium carteri;
(3) as in category (2), but with plug-like structures associated with the inner side of the vesicles;
these plugs are cylindrical structures 120 nm long, and are arranged in single lines between
single or paired microtubules; an example of this arrangement is present in Gymnodinium venefi-
cum; (4) as in category (2), but with thin (about 20 nm) plate-like structure in the flattened vesicles;
this amphiesma characterizes Aureodinium pigmentosum; (5) in this group the vesicles contain
plates of medium thickness (60 nm), which slightly overlap; in Woloszynskia coronata the plates
are perforated by trichocyst pores; (6) the plates are thicker (up to 150 nm), reduced in number
with a marked diversity of form; each plate has two or more sides bearing ridges and the remaining
sides have tapered flanges; where the plates join, one plate bears a ridge and the opposite bears a
flange; Glenodinium foliaceum belongs to this category; (7) the plates can be up to 25 mm large and
up to 1.8 mm thick; they bear a corrugated flange on two or more sides, and a thick rim with small
projections on the opposing edges; these plates may overlap to a considerable extent, and their
surface may be covered by a pattern of reticulations; a distinctive member of this category is
Ceratium sp.; and (8) amphiesma consisting of two large plates, with one or more small plates
in the vicinity of the flagellar pores at the anterior end of the cell; plates can be very thin and
perforated by two or three simple trichocyst pores as in Prorocentrum nanum, or thick and with
a very large number (up to 60) of trichocyst pores as in Prorocentrum micans (Figure 2.18).
The arrangement of thecal plates is termed tabulation, and it is of critical importance in the
taxonomy of dinoflagellates. Tabulation can also be conceived of as the arrangement of amphies-
mal vesicles with or without thecal plates. The American planktologist and parasitologist Charles
Kofoid developed a tabulation system allowing reference to the shape, size, and location of a par-
ticular plate; plates were recognized as being in series relative to particular landmarks such as the
apex, cingulum (girdle), sulcus. His formulas (i.e., the listing of the total number of plates in each
series) were especially useful for most gonyaulacoid and peridinioid dinoflagellates. Apart from
some minor changes introduced afterwards, the Kofoid System is still the standard in the descrip-
tion of new taxa. Plates are numbered consecutively from that closest to the midventral position,
continuing around to the cell left. A system of superscripts and other marks are used to designate
0
the plate series. Two complete transverse series of plates are present in the epitheca: apical ( ) and
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precingular ( ), counted from the ventral side in a clockwise sequence. Also the hypotheca is
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divided into two transverse series: postcingular ( ) and antapical ( ). Some genera possess also
an incomplete series of plates on the dorsal surface of the epitheca, termed anterior intercalary
plates (a), and on the hypotheca, termed posterior intercalary plates (p). Cingular (C) and sulcal (S)
plates are also identified (Figure 2.19). Thus, for example, the dinoflagellate Proteperidinium
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steinii has a formula 4 , 3a, 7 , 3C, 6S, 5 ,2 , which indicates four apical plates, three anterior
intercalary plates, seven precingular plates, three cingular plates, six sulcal plates, five postcingular
plates, and two antapical plates.