Thalassionema cf. nitzschioides HK

Sabir, J. S. M., Theriot, E. C., Lobban, C. S., Alhebshi, A. M., Al-Malki, A. L., Hajrah, N. H., Khiyami, M. A., Obaid, A. Y., Jansen, R. K. & Ashworth, M. A., 2018, Systematics of araphid diatoms with asymmetric rimoportulae or densely packed virgae, with particular attention to Hyalosynedra (Ulnariaceae, Bacillariophyta), Phytotaxa 347 (1), pp. 1-49 : 29

Thalassionema cf. nitzschioides HK 360 ( Figs 73–77 )

Synonym: Thalassionema cf. frauenfeldii HK 360 in Edward C. Theriot, Nakov et al. (2014), Lobban and Ashworth (2014a,b), Theriot et al. (2015). Material studied: —Wild and cultured ( HK 360) material isolated from the same collection: ECT3929, collected by plankton net from the Gulf of Mexico, Texas, USA (27° 38.06’ N; 96° 42.21’ W).

Description:— Valve lengths were 58–65 μm, and widths were 3.3–3.9 μm. The areolar bars were observed to have a broad base at the top of the areola, tapering to a point towards the margin. Valves were convex in the middle with protracted, weakly subcapitate ends. Areolar densities were 8–9 in 10 μm. Girdle bands were open and without pores.

Remarks:— This diatom keyed out to T. nitzschioides in both Sugie and Suzuki (2015) and in Hasle (2001). However, it was quite different in details of the description. The areolae were covered by a simple bar rather than the complex Y- or X- shaped features illustrated elsewhere for this species ( Hasle 2001, Sugie & Suzuki 2015). Hasle (2001) and Sugie and Suzuki (2015) each reported specimens with entirely convex margins becoming linear and parallel in smaller specimens, whereas our specimens were convex in the center with protracted ends. Areolar density of our specimens was at the coarse end for that reported for T. nitzschioides ( Sugie and Suzuki 2015) . DNA sequences for this strain were previously reported as Thalassionema cf. frauenfeldii HK 360/ECT3929ThalXL in Lobban and Ashworth (2014a,b).

Figures

FIGURES 73–77. Thalassionema cf. nitzschioides from culture HK360. 73. Exterior, whole valve. 74. Exterior, right facing apex from 73. 75. Exterior, left facing apex from 73. 76. Interior, whole valve. 77. Interior, detail of apex.