Vikingea gibbocalyx (Brun) Witkowski, Lange-Bertalot & Metzltin

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 : 17

Vikingea gibbocalyx (Brun) Witkowski, Lange-Bertalot & Metzltin Figs 111–113

Ref. illus.: Witkowki et al. 2000, p. 125, pl. 55, figs 8–16, pl. 56, figs 1–3, 5, pl. 57, figs 1–4; Hein et al. 2008, p. 40, pl. 16, fig. 25; Van de Vijver et al. 2009, figs 1–34, Riaux-Gobin et al. 2011, p. 40, pl. 81, figs 1–3, pl.82, figs 1–6

Dimensions: Length 25–28 µm, width 17–20 µm; striae 9 in 10 µm ( RV), 7–8 in 10 µm (SV)

Samples: GU52X-5, GU52N-7, GU52P-3

Diagnostics: The raised apices of the RV are diagnostic of the genus in LM, the large circular central area diagnostic of the species in contrast to V. florifera Riaux-Gobin, O.E.Romero, Compère & A.Y.Al-Handel (2011) , which has a broad fascia.

Comments: These specimens are in the lower end of the size range compared to most literature (see van de Vijver et al. 2009, table 1). There are two troubling differences between our specimens and those shown in the recent literature. First, comparison of the internal SV in our Fig. 112 with figs 16, 19 in van de Vijver et al. (2009) and similar images in Witkowski et al. (2000) and Riaux-Gobin et al. (2011) shows absence in our specimen of the elliptical opening and slit in the marginal ridges; this may be significant even though it was also absent in some specimens by van de Vijver et al. (2009, fig.20). Secondly, Van de Vijver et al. (2009: 271, fig. 27, arrow) show small costae extending from the RV margin into the first row of areolae, a feature clearly absent from the external RV shown in Fig. 113 . This is yet another genus with strong potential for additional species to be found.

Figures

Figures 111–113. Vikingea cf. gibbocalyx. Fig. 111. Raphe valve in LM. Fig. 112. Sternum valve, exterior in SEM. Fig. 113. Broken frustule showing external raphe valve Scale bars: Fig. 111 = 10 µm, Figs 112, 113 = 5 µm.