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* Mentioned in the text for comparison.

* Mentioned in the text for comparison.

p. 169, Plate 22.1, Figs 1-7 and 10; Hasle, 1994, Fig. 3; Hasle et al., 1996, Figs. 10-14 and 45-49. Girdle view: Linear to fusiform with distinctly pointed ends; overlap of cells in chains one-third to one-fourth of cell length. Valve view: One margin of middle part almost straight and the other convex; both margins tapering toward more or less rounded apices. Interstriae of well-silicified specimens discernible in water mounts and readily seen on cleaned valves on permanent mounts. Canal raphe along either curved or straight margin.

Pseudo-nitzschia seriata f. obtusa (Hasle) Hasle Basionym: Nitzschia seriata f. obtusa Hasle.

References: Hasle, 1965b, p. 10, Plate 3, Figs. 8, 9, and 11; Hasle, 1974, p. 426; Hasle &C Medlin, 1990c, p. 169, Plate 22.1, Figs. 8, 9, and 11; Hasle 1993, p. 319; Hasle et al., 1996, Figs. 15 and 50. Valve view: Same as the nominate form but smaller and with distinctly rounded apices. Specimens in which the valve structure is not resolved may be confused with Thalassionema nitzschioides.

Pseudo-nitzschia australis Frenguelli (Plate 69, Table 74) Synonym: Nitzschia pseudoseriata Hasle.

References: Frenguelli, 1939, p. 217, Plate 2, Fig. 13; Hasle, 1965b, p. 11, Plate 5, Figs. 1-6, Plate 6, Fig. 1; Rivera, 1985, p. 13, Figs. 14-18; Hasle et al., 1995, Figs. 16 and 51-54.

Girdle view: Fusiform; overlap of cells in chains ca. one fourth of cell length (Rivera, 1985, Figs. 15 and 16). Bands strongly silicified with transverse ribs somewhat more closely spaced than those on the valves (Hasle, 1965b, Plate 5, Fig. 6).

Valve view: Larger (apical axis more than ca. 100 /xm) specimens with slightly rostrate ends. Middle, about one third part of valve with more or less parallel margins, sometimes less distinct in smaller specimens. Fibulae more distinct than interstriae, both readily seen with LM. Remarks: Rivera (1985) rejected Nitzschia pseudoseriata (= P. australis) as a taxon of its own, separated from Nitzschia seriata, his argument being the great variation in his Chilean material. Pseudo-nitzschia australis is larger, generally coarser, and more symmetrical with respect to the apical plane than P. seriata. Also, the valve striae of P. australis bear two rows of poroids and those of P. seriata three or four, and the poroids of P. australis are larger than those of P. seriata (Hasle, 1965b; Hasle et al., 1995).

Pseudo-nitzschia pungens (Grunow ex Cleve) Hasle (Plate 69, Table 74) Basionym: Nitzschia pungens Grunow ex Cleve. References: Grunow (in Cleve 8c Möller, 1882), No.307; Cleve, 1897a, p. 24, Plate 2, Fig. 23; Cupp, 1943, p. 202, Fig. 156; Hasle, 1965b, p. 12, Plate 1, Figs. 4 and 5, Plate 5, Figs. 7-9; Takano 8c Kuroki, 1977, p. 42, Figs. 1 and 4-8; Rivera, 1985, p. 12, Figs. 1-3; Takano 8c Kikuchi, 1985; Takano, 1990, pp. 328-329; Hasle, 1993, p. 319; Hasle et al., 1996, Figs. 3-6 and 30-37; Hasle, 1995, Fig. 1. Girdle view: Fusiform, pervalvar axis up to 8 ju,m. Fibulae and/or ends of interstriae distinct. Overlap of cells in chains considerable, close to one-third or more of cell length.

Valve view: Larger specimens linear with distinctly pointed ends, and smaller specimens more fusiform. Strongly silicified. Interstriae visible in water mounts. Fibulae distinct on cleaned valves on permanent mounts; striae biseriate; the two rows of poroids discernible with LM under optimum optical conditions (phase contrast, oil immersion).

Pseudo-nitzschia multiseries (Hasle) Hasle (Table 74) Basionym: Nitzschia pungens f. multiseries Hasle. Synonym: Pseudo-nitzschia pungens f. multiseries (Hasle) References: Hasle, 1965b, p. 14, Plate 2, Figs. 1 and 2, Plate 5, Figs. 10-12; Hasle, 1974, p. 426; Takano 8c Kuroki, 1977, p. 43, Figs. 2 and 9-13; Subba Rao 8c Wohlgeschaffen, 1990; Fryxell et al., 1990, p. 171; Takano, 1990, pp. 328-329; Hasle, 1993, p. 319; Hasle et al., 1996, Figs. 7-9 and 38-44; Hasle, 1995, Fig. 2; Manhart et al., 1995. Valve view: Multiseriate striae, not resolved with LM. Smaller and medium-sized specimens on an average broader compared to valve length than the same sized specimens of P. pungens.

Remarks: Since the poroids do not resolve with LM, EM is necessary to ascertain the identification of this species. Takano 8c Kikuchi (1985) reported on P. pungens cells with swellings from the girdle and undulated valves from eutrophic marine Japanese waters. Subba Rao 8c Wohlgeschaffen (1990) found similar cells of P. multiseries in cultures and in naturally very dense populations. Beaked and lobed valve margins, such as those shown in these investigations, are common in dense, unhealthy cultures of Pseudo-nitzschia in general (Hasle, 1965b, Plate 2, Fig. 9) and are also comparable to the forms of Synedropsis hyperborea found in nature (Grunow, 1884, Plate 2, Figs. 4-6) and in cultures (Hasle et al., 1994). The occurrence of aberrant cells of P. multiseries should be no obstacle for a correct identification since the cells retain most of their specific morphological characters.

2. Slightly more interstriae than fibulae; central larger interspace present.

Pseudo-nitzschia pungiformis (Hasle) Hasle (Table 74) Basionym: Nitzschia pungiformis Hasle.

References: Hasle, 1971, p. 143, Figs. 1-8; Simonsen, 1974, p. 54, Plate 40, Figs. 1 and 2; Hasle, 1993, p. 319. Valve view: Larger specimens with almost parallel margins for their greater length; smaller specimens fusiform, valve ends slightly pointed. Fibulae, interstriae, and the central larger interspace readily recognized on cleaned valves on permanent mounts (LM). Number of fibulae and interstriae generally the same in the middle part of the valve with a slight deviation toward the valve ends. The biseriate structure of the striae not resolved with LM.

Pseudo-nitzschia fraudulenta (Cleve) Hasle (Plate 70, Table 74) Basionym: Nitzschia fraudulenta Cleve. Synonym: Pseudo-nitzschia seriata var. fraudulenta (Cleve) H. Peragallo in H. 8c M. Peragallo.

References: Cleve, 1897b, p. 300, Fig. 11; H. 8c M. Peragallo, 1897-1908, p. 300, Plate 72, Fig. 29; Hasle, 1965b, p. 15, Plate 1, Figs. 2 and 3, Plate 6, Figs. 5-10; Takano 8c Kuroki, 1977, p. 43, Figs. 14-18; Rivera, 1985, p. 15, Figs. 43-46; Hasle, 1993, p. 318; Hasle, 1994, Fig. 4; Hasle et al., 1996, Figs. 17-19 and 57-61. Girdle view: Linear to fusiform; overlap of cells in chains fairly short. Valve view: Fusiform. Weakly silicified; valve structure not discernible in water mounts. Fibulae and central nodule distinct on cleaned valves on permanent mounts; interstriae barely discernible (LM). Remarks: Pseudo-nitzschia subfraudulenta (Hasle) Hasle (basionym: Nitzschia subfraudulenta) is a less frequently recorded species which is very

P. subfraudulenta

P. subpacifica

similar to P. fraudulenta but differs in morphometric data and by having more linear valves, especially in the middle part (Hasle et al., 1996, Fig. 62).

3. More than one interstria per fibula; central larger interspace present; transapical axis heteropolar; canal raphe along either convex or straight margin.

Pseudo-nitzschia heirnii Manguin (Plate 70, Table 74) Synonym: Nitzschia heirnii (Manguin) Hasle.

References: Manguin, 1957, p. 131, Plate 6, Fig. 42; Manguin, 1960, p. 332, Plate 19, Figs. 223 and 224; Hasle, 1965b, p. 21, Plate 1, Figs. 6 and 7, Plate 10, Figs. 9-13; Simonsen, 1974, p. 51, Plate 36, Figs. 4 and 5; Hasle & Medlin, 1990c, p. 169, Plate 22.2, Figs. 9-13; Hasle et al., 1996, Figs. 20 and 65-69. Girdle view: Linear, tapering toward somewhat sigmoid and obliquely truncated poles; overlap of cells in chains one-fourth to one-fifth of cell length.

Valve view: Largest specimens almost fusiform; smaller specimens with one convex and one straight margin attenuated toward broadly rounded, obtuse ends, sometimes with a constriction near apices. Fibulae, central larger interspace, central nodule and interstriae readily seen on cleaned valves on permanent mounts (LM).

Pseudo-nitzschia subpacifica (Hasle) Hasle (Plate 70, table 74) Basionym: Nitzschia subpacifica Hasle.

References: Hasle, 1965b, p. 20, Plate 1, Figs. 9 and 10, Plate 10, Figs. 1-8; Hasle, 1974, p. 427; Simonsen, 1974, p. 55, Plate 41, Figs. 1-3; Hasle, 1993, p. 320.

Girdle view: Slightly convex margins; sigmoid, obliquely truncated cell ends; overlap of cells in chains one-fifth to one-sixth of cell length. Valve view: One margin convex, the other more or less straight especially in the middle two-thirds of valve length; valve ends more or less pointed. Canal raphe somewhat indented in the middle; central larger interspace and central nodule observable on cleaned valves on permanent mounts, interstriae barely discernible (LM).

PLATE 70 Pseudo-nitzschia fraudulenta: (a) partial chains in valve and girdle views; (b) valve with striation and central larger interspace. Pseudo-nitzschia subfraudulenta: valves with striation and central larger interspace. Pseudo-nitzschia heirnii: (a) partial chains in valve and girdle views; (b) valve with striation and central larger interspace. Pseudo-nitzschia subpacifica: (a) partial chains in valve and girdle views; (b) valve with striation and central larger interspace. From Hasle (1972d). Scale bars = 10 /im.

Distribution (Hasle 1972d): P. seriata f. seriata—northern cold water region to temperate. P. seriata f. obtusa—northern cold water region.

P. australis, P. subfraudulenta, and P. subpacifica—warm water region to temperate.

P. pungiformis—warm water region.

P. pungetis, P. multiseries, P. fraudulenta, and P. beimii—cosmopolitan. Pseudo-nitzscbia beimii is particularly abundant in the subantarctic. The presence of P. australis in the north Pacific should be noted (Hasle, 1972d, Fig. 2, confirmed by personal observations of net samples from Monterey Bay, August 7, 1967 and July 14, 1982, and in September 1991 by Work et al., 1991). How to identify: In general, the species of the "Nitzscbia seriata complex" can only be identified to genus and not to species when examined in girdle view. A few of the larger species are coarsely structured and are identifiable in valve view in water mounts. Most of them have to be examined as cleaned valves mounted in a medium of a high refractive index.

B. Transapical axis ca. 3 /xm or less.

With a few exceptions the diatoms of this so-called "Nitzscbia delicatissima complex" (Hasle, 1965b) are delicate forms with a very fine structure. Electron microscopy reveals two types of stria structure, either well-defined circular

TABLE 75 Morphometric Data of Pseudo-nitzschia spp. of the "Nitzscbia delicatissima Complex" (Hasle, 1964, 1965b)

Species

Apical axis (jim)

Transapical axis (jim)

Striae in 10 |un

Fibulae in 10 n-m

Group B1

P. delicatissima 40-76 ca. 2

P. prolongatoides 20-70 0.5-2.5

P. turgiduloides' 63-126 1.2-2.7 Group B2

P. cuspidata 30-80 ca. 3

P. pseudodelicatissima 59-140 1.5-2.5

P. subcurvata 47-113 1.5-2.5

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