Key To Species

la. Cells in ribbons partly or not in touch 2

lb. Cells in tight ribbons 3

2a. Cells united by a mucilage pad in the central nodule area with threads ("setae") attached, two comma- or pear-shaped chloroplasts per cell. . .

N. pelagica Cleve

2b. Cells in colonies widely separated, two plate-like chloroplasts per cell . .

N. vanhoeffenii Gran

3a. Cells united by the entire valve faces, one chloroplast per cell, with four arms and large central pyrenoid . . . .N. septentrionalis (Grunow) Gran 3b. Cells not touching at apices and in the center, two rectangular chloroplasts per cell, each with large central pyrenoid . . N. granii (Jorgensen) Gran

Basionyms: Stauroneis septentrionalis Grunow; Stauroneis granii Jargensen. Synonyms: Stauropsis pelagica (Cleve) Meunier; Stauropsis vanhoeffenii (Gran) Meunier; Stauropsis granii (Jorgensen) Meunier; and Navicula quadripedis Cleve-Euler [regarded by VanLandingham (1975, p. 2796) as the valid name for Navicula septentrionalis Gran, 1908 (Fig. 167)]. Distribution: Northern cold water region

How to identify: These species may be distinguished in chains in water mounts.

Remarks: The setae-like structures in N. pelagica are dislocated girdle bands (Syvertsen, 1984). Navicula pelagica is also distinguished by the

PLATE 61 Navicula granii: ribbon in girdle view with characteristic chloroplasts. Navicula pelagica: twisted chain in girdle view with dislocated bands. Navicula vanhoeffenii: ribbon in girdle view, cells not touching, square chloroplasts. Navicula septentrionalis: ribbon in girdle view, lens-shaped structure between cells, chloroplasts lobed. Scale bars = 10 /¿m.

arrangement of cells in chains, which is rotated approximately 50° on the chain axis in relation to its neighboring cell.

3. Former solitary Navicula spp.

Genus Haslea Simonsen 1974

Type: Haslea ostrearia (Gaillon) Simonsen.

Basionym: Vibrio ostrearius Gaillon.

Synonym: Navicula ostrearia Turpin in Bory de St.-Vincent: References: Hustedt, 1961, p. 34 as Navicula fusiformes, Simonsen, 1974, p. 46; Cox, 1979.

Haslea comprises 13 species (Simonsen, 1974), all of which are marine; some of them are planktonic and some are associated with a substratum, e.g., ice (Poulin, 1990). Three, apparently more commonly recorded planktonic species, distinguished by size, fineness of structure, and distribution, are included here.

Generic characters:

Cells solitary (or in mucilage tubes = benthic forms).

Cell wall weakly silicified.

Cells generally fusiform in girdle and valve views. Valves narrow and linear to lanceolate, valve ends pointed. Transverse and longitudinal striae crossed at right angles. Raphe central pores small and approximate. Chloroplasts, two plate like (H. ostrearia).

Von Stosch (1986) observed many small bacilliform or roundish chloroplasts in H. gigantea and two in H. wawrikae which in old cultures seemed to divide into numerous small platelets.

Haslea gigantea (Hustedt) Simonsen (Table 69) Basionym: Navicula gigantea Hustedt.

TABLE 69 Morphometric Data of Haslea spp.

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