Biremis ambigua (Cleve) D.G.Mann

Lobban, Christopher S. & Witkowski, Andrzej, 2023, Marine benthic diatoms of Guam: new records, Dictyoneis apapae sp. nov., and updates to the checklist, Micronesica 2023 (2), pp. 1-75 : 6

Biremis ambigua (Cleve) D.G.Mann Figs 30, 31

Ref. illus.: Cox 1990, figs 19–28; Sabbe et al. 1995, figs 34, 35, 38, 51, 52; Witkowski et al. 2000, p. 158, pl. 155, figs 2–6; Tatarek & Wiktor 2005

Samples: GU52O-4

Dimensions: Length 38–54 µm, width ca. 6 µm; striae 9–10 in 10 µm

Diagnostics: Linear, symmetrical valve, similar in size and stria density to B. ridicula (see below), which is strongly asymmetrical.

Comments: Biremis is characterized by alveolate striae. Several smaller species have been observed but not yet identified.

Figures

Figures 26–31. Biddulphiella and Biremis. Figs. 23–26. Biddulphiella tridens. Fig. 26. Frustule in valve view at two focal planes. Figs 27, 28. Valves in girdle and valve view, respectively, SEM. Fig. 29. Valve in oblique view, emphasizing the deep grooves (sulci) between the elevations. Figs. 30, 31. Biremis ambigua frustules in SEM. Fig. 30. Oblique view showing raphe and paired external alveolus openings. Fig. 31. Broken frustule showing internal side of alveoli (arrow) and exterior of girdle bands. Scale bars = 10 µm.