Pinnularia sp. 2

Furey, Paula C., Manoylov, Kalina M. & Lowe, Rex L., 2020, New and interesting aerial diatom assemblages from southwestern Iceland, Phytotaxa 428 (3), pp. 173-208 : 198-199

Pinnularia sp. 2 (LM = Fig. 11 C )

Valves linear with parallel margins and broadly rounded, not protracted ends (length 65–72 μm, valve width 12–13 μm, 5 striae in 10μm, for n=5 LM). Axial area narrow, linear. Central area rounded more than ½ of the width of the valve, asymmetrical in the middle due to the shortening of some striae on one side and on the other no visible striae on valve face and central area reaching margin. Raphe moderately lateral, slightly arcuate. Proximal raphe ends deflected towards one side and curved, no visible central pores.

Pinnularia stomatophora (Grunow in A. Schmidt et al. 1876: pl. 44) Cleve (1895: 83) (LM = Fig. 11 B )

Valves broadly elliptic-lanceolate with convex sides and broadly rounded, sometimes protracted, ends (length 83 μm, width 9.5–10 μm, 13–14 striae in 10μm). Axial area narrow, slightly linear-lanceolate, widening towards the middle. Central area has a broad fascia, enlarging towards the valve margins. Raphe filiform, weakly curved with clearly enlarged central pores. Terminal fissures strongly hooked. Transapical striae weakly radiate and even sinuous in the middle, more and more convergent towards the apices. Longitudinal lines absent. This taxon has been reported from cold habitats ( Cantonati et al. 2017).

Pinnularia cf. subcommutata Krammer (1992: 136) (LM = Fig. 11 A )

Valves linear with obtusely rounded ends. Our specimen was a little bit longer than reported in the literature (thus we chose to keep a cf. designation): length 76 μm, width 9 μm, 12 striae in 10μm, length in literature 40–70 μm (Krammer 2000). Axial area moderately broad, widening towards the central area. Central area elliptical. Raphe moderately lateral with bent central endings and distinct central pores. Terminal fissures shaped as hooks. Striae radiate in the middle, parallel towards the poles. A longitudinal band is present. Asymmetrically missing striae.

Sellaphora seminulum ( Grunow 1860: 552) D.G. Mann (1989: 2) (LM = Fig. 10 c )

In current literature Navicula seminulum var. radiosa Hustedt (1954: 473) ( Fig. 10 b ) is a synonym of S. seminulum ( Wetzel et al. 2015) . However, we kept S. seminulum separate from the N. seminulum var. radiosa based on the less convex margins and narrower width for N. seminulum var. radiosa . The complex is known from intermittently-drying small water bodies.

Stauroforma atomus ( Hustedt 1931: 164) D. Talgatti, C.E. Wetzel, E. Morales et L.C. Torgan (2014: 45) (LM = Fig. 2 O–P ) known to survive in brackish conditions ( Talgatti et al. 2014). Our specimens were thinner and longer than given in the literature, length 8–9 μm, width 2.4–2.6 μm, striae 16 striae in 10 μm (for n=10 LM) as compared with the type population length 4.5–7 μm, width 2.5–3.5 μm, striae 16 striae in 10 μm, but it fits Cantonati et al. (2017). Has been reported from Iceland as Fragilaria atomus Hustedt 1931: 164 ( Hallgrímsson 2007) and Fragilariforma atomus ( Hustedt 1931: 164) Lange-Bertalot in Hofmann, Werum & Lange-Bertalot 2011: 257

( Cantonati et al. 2017).

Figures

FIGURE 2. Light (B–T) and SEM (A, U–V) microscopy images of diatom assemblages from aerial sites in southwestern Iceland. A–G. Staurosirella neopinnata:A. external, girdle view of two linked frustules, left frustule shows the completed synthesis of new valves within the frustule, B–D. size series in valve and E–G. girdle view, F and G. two linked frustules; H. Fragilaria nitzschioides: valve view; I–J. Meridion circulare var. constrictum: I. 2 frustules in girdle view, J. valve view; K. Fragilaria perminuta: valve view; L–M. Aulacoseira alpigena: L. girdle view and M. valve view; N, S–T. Orthoseira roeseana: N. girdle view with irregular linking spines and longitudinal areolae on the valve mantle, S–T. Valve view with 3 to 4 carinoportulae; O–P. Stauroforma atomus: valve views; Q, R, U–V. Hygropetra balfouriana: Q–R. valve view, U. SEM of a tilted frustule with both valve and girdle views visible, U. shows the nature of the striae, and raphe, V. internal view. LM scale bar = 10 μm, SEM scale bars as shown.

FIGURE 10. Light (B–z) and SEM (A) microscopy images of aerial diatom assemblages from southwestern Iceland, mostly in valve view. A–E.Diatomella balfouriana:A, D–E.girdle views, B. valve viewwith striae infocus,C.septa with openings infocus; F.Encyonema langebertalotii; G. Gomphonema sp. 1; H. Gomphonema bipunctatum; I. Cymbopleura cf. subaequalis, J. Naviculoid sp. 1; K. Amphora ovalis; L. Tryblionella debilis; M–O, a. Platessa rupestris var. interrupta; P–Q. Platessa rupestris; R. Adlafia bryophila; S–U. Microcostatus krasskei; V. Neidium bisulcatum; W. Hantzschia amphioxys; X. Navicula cf. radiosa; Y–Z, a. Psammothidium marginulatum; b. Navicula seminulum var. radiosa; c. Sellaphora seminulum; d–e. Fallacia insociabilis; f. Brachysira brebissonii; g. Naviculoid sp. 2; h–i. Adlafia suchlandtii j= Luticola c.f. nivaloides, k. Luticola sp. 1; l. Luticola cf. mutica; m. Sellaphora rectangularis; n. Cavinula variostriata; o Nitzschia sinuata; p–q, s–v. Nitzschia perminuta; r. Nitzschia soratensis, w. Diploneis ovalis; x–y. Rhoicosphenia cf. californica; z. Rhoicosphenia abbreviata. Scale bar =10 μm unless stated otherwise shown, ‘=’ represents focus on each valve of the same frustule.

FIGURE 11. Light microscopy images of aerial diatom assemblages from southwestern Iceland. A. Pinnularia cf. subcommutata; B. Pinnularia stomatophora; C. Pinnularia sp. 2; D. Pinnularia sp. 1; E. Pinnularia borealis; F. Pinnularia borealis f. subcapitata; G. Pinnularia borealis var. islandica girdle view; H. Pinnularia borealis var.lanceolata; I–J. Pinnularia intermedia; K–M. Pinnularia parva; N–O. Pinnularia minoricapitata; P. Muellaria gibulla; Q. Achnanthes coarctata; R. Caloneis schumanniana; S–T. Caloneis silicula; U–W. Caloneis tenuis; X–a. Stauroneis cf. borrichii. LM scale bar = 10 μm.