Info

Note: —, No data; number in parentheses occasionally found.

Each valve with a marginal bilabiate process, the external part a low ring, and the internal part with a long stalk.

Valve structure not resolvable with LM.

Chloroplasts numerous and rounded.

KEY TO SPECIES (von Stosch, 1987, p. 82)

la. Ribbons (or solitary), flat, valves oblique to girdle in broad girdle view

N. subindica von Stosch lb. Chains (or solitary) twisted or spiraled, valves oblique or sometimes perpendicular to girdle in broad girdle view N. torta von Stosch

Distribution: Warm water region.

Remarks: Von Stosch (1987) described Neostreptotheca torta with the form triangularis from Australian plankton. Neostreptotheca torta f. torta sometimes has rectangular cells and is thus habitually similar to Helicotheca from which it differs by a special structure around the base of the process which is revealed with TEM.

Family Eupodiscaceae Ktitzing 1849

Odontella is the only genus included in Eupodiscaceae sensu Simonsen, 1979 that has typically marine planktonic species. Round et al. (1990) placed Odontella in Triceratiaceae (Schutt) Lemmermann, order Triceratiales Round & Crawford, subclass Biddulphiophycidae Round 8c Crawford, and Glezer et al. (1988) placed Odontella in Biddulphiaceae Kutzing, order Biddulphiales.

The species listed in this chapter as Odontella spp. were previously regarded as Biddulphia spp. SEM investigations of genera of Biddulphiaceae showed, however, that they belong in Odontella partly because they have ocelli and labiate processes with long external tubes (Ross 8c Sims, 1971; Simonsen, 1974) whereas Biddulphia has pseudocelli.15 Which species really belong to Odontella is still disputed (Round et al., 1990); here we include those which are usually regarded as planktonic.

Genus Odontella C. A. Agardh 1832 (Plate 49, Table 62) Type: Odontella aurita (Lyngbye) C. A. Agardh. Basionym: Diatoma aurita Lyngbye. Synonym: Biddulphia aurita(Lyngbye) Brebisson.

15 Pseudocellus—field of areolae decreasing in size from those on the main part of the valve.

PLATE 49 Odontella aurita: (a) short chain; (b) valve view. Odontella sinensis: single cell with characteristic processes. Odontella mobUiensis: single cell, processes, and horns. After Cupp (1943). Odontella longicruris: single cell, processes, and horns. After Cupp (1943). Scale bars = 20 fim.

O. mobiliensis

TABLE 62 Morphometric Data of Odontella spp.

Valve areolae in

Species Apical axis (|xm) 10 p.m Band areolae in 10 p.m

TABLE 62 Morphometric Data of Odontella spp.

Valve areolae in

Species Apical axis (|xm) 10 p.m Band areolae in 10 p.m

O. aurita

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