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Haslea trompii

Pleurosigma directum

Pleurosigma normanii

PLATE62 Haslea wawrikae: valve outline. After Soumia (1968). Scale bar = 50 p.m. Haslea trompii: (a) valve view. Scale bar = 50 p.m; (b) valve structure. After Hustedt (1961). Scale bar = 10 /im. Pleurosigma normanii: (a) valve view. Scale bar = 20 /im; (b) valve end, structure. After Cupp (1943). Scale bar = 10 /im. Pleurosigma directum: valve view. After Peragallo (1891). Scale bar = 20 /im.

References: Hustedt, 1961, p. 40, Fig. 1194; Simonsen, 1974, p. 47, Plate 31, Fig. 1; von Stosch, 1986, p. 333, Fig. 20. Valves lanceolate. Raphe straight, central pores extremely close. No visible sternum. Striation discernible with LM (interference contrast).

Haslea trompii(Cleve) Simonsen (Plate 62, Table 69) Basionym: Navicula trompii Cleve.

References: Cleve, 1901b, p. 932, Fig. 11; Hustedt, 1961, p. 40, Fig. 1195; Simonsen, 1974, p. 47. Valves lanceolate. Raphe straight; central pores extremely close. No visible sternum. Longitudinal interstriae more distinct than the transverse ones and readily observed with LM.

Haslea wawrikae (Hustedt) Simonsen (Plate 62, Table 69) Basionym: Navicula wawrikae Hustedt.

References: Hustedt, 1961, p. 52, Fig. 1204; Simonsen, 1974, p. 48; von Stosch, 1986, p. 339, Fig. 23. Valves extremely narrow and spindle shaped with long, almost rostrate, ends. Raphe with very long terminal nodules. Transapical striae discernible with LM (phase or interference contrast).

The pervalvar axis of H. wawrikae is 4-7 fim and that of H. gigantea is 30-70 ju,m, whereas H. gigantea var. tenuis is smaller in all dimensions (von Stosch, 1986).

Distribution:

H. gigantea and H. wawrikae—warm water region. H. trompii—southern cold water region. How to identify: Haslea wawrikae may be identified by the narrowness of the cells. The valve striation may be seen by using dry mounts [cells or single valves mounted in air (von Stosch, 1986)] or on valves mounted in a medium of a high refractive index.

4. Present solitary Navicula spp.

Most of the solitary Navicula species found in marine plankton have been stirred up from the bottom or detached from some type of substrate. Navicula transitans var. derasa is common on Arctic sea ice (Poulin, 1990) but is also found in the plankton. The form delicatula, described by Heimdal (1970) from a fjord in northern Norway, is common in Norwegian coastal waters in general. Navicula directa and N. distans are primarily bottom dwelling species but are often found in the plankton (Gran & Angst, 1931; Hendey, 1964).

PLATE 63 Navicula directa: (a) valve with chloroplasts; (b) valve structure. After Gran 8c Angst (1931). Navicula distans: (a) valve with chloroplasts; (b) valve structure. After Gran 8c Angst (1931). Navicula transitrans: (a) var. derasa, valve with chloroplasts. After Heimdal (1970); (b) var. derasa, valve structure. After Cleve 8c Grunow (1880); (c) f. delicatula, valve with typical chloroplasts. After Heimdal (1970). Scale bars = 10 /um.

TABLE 70 Morphometric Data of Solitary Navícula spp.

Striae in 10 |tm

Transapical axis

Species Apical axis (|*m) (|im) Transverse Longitudinal

TABLE 70 Morphometric Data of Solitary Navícula spp.

Striae in 10 |tm

Transapical axis

Species Apical axis (|*m) (|im) Transverse Longitudinal

N. directa

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