Pseudostaurosira vulpina (Lange-Bertalot & U. Rumrich) E. Morales, 2021

Morales, Eduardo A., Wetzel, Carlos E. & Ector, Luc, 2021, New and poorly known " araphid " diatom species (Bacillariophyta) from regions near Lake Titicaca, South America and a discussion on the continued use of morphological characters in " araphid " diatom taxonomy, PhytoKeys 187, pp. 23-70 : 23

Pseudostaurosira vulpina (Lange-Bertalot & U. Rumrich) E. Morales stat. nov.

Figs 6A-D (LM), 7A-F (SEM)

Basionym.

Staurosira laucensis var. vulpina Lange-Bertalot & U. Rumrich in Rumrich et al. 2000, Diatoms of the Andes from Venezuela to Patagonia/Tierra Del Fuego, Iconographia Diatomologica 9, p. 223-224, Plate 10, Figs 1-11.

Comment.

This taxon was first described from the Chilean Altiplano and was found mixed with the nominate variety Pseudostaurosira laucensis (Lange-Bertalot & Rumrich) E. Morales & Vis (in Rumrich et al. 2000, p. 222, figs 10-20, 22, 23; Morales and Vis 2007, p. 25). This was the probable reason why Lange-Bertalot and Rumrich (in Rumrich et al. 2000) decided to describe it as a variety. However, we found the Pseudostaurosira laucensis var. vulpina isolated from the nominate variety in the Desaguadero River sample. This population, like the one reported from Chile, exhibits a range of sizes which is probably showing that it is undergoing asexual reproduction and its size is most probably being re-established through sexual reproduction.

At the LM level, this taxon is distinguished by its typical triradiate shape (Fig. 6A-D ). Between each of the arms there is also a central inflation that becomes more pronounced as the valve decreases in size (Fig. 6C, D ). At the SEM level, the axial area is depressed in external view with respect to the virgae, while internally it is at the same level as the latter. Each of the arms has an apical pore field that lies within a shallow, irregular depression (Fig. 7A-C ) and opens to the valve interior as a plain plate of pores (Fig. 7F ). The transapically elongate areolae bear well-developed volae (Fig. 7A-E ), which allow inorganic deposition of an inverted cone-like structure internally covering the areolae, sometimes filled with extra depositions in their hollow interior (Fig. 7F ). The spines are conical, but also it is common to find them as incipient, shapeless spines that are generated from the virgae and the vimines (Fig. 7E ). The girdle elements vary in number, lack perforations and all are open (Fig. 7E ). The valvocopula is wider. At the open side, each element has its terminations superimposing each other (Fig. 7E ).

Dimensions (n> 10): Length (from the extreme of one arm to the other) 4.8-13.0 μm; width (from one swollen central area to its opposite side) 4.1-5.6 μm; stria density (measured from arm to arm) 14-16 in 10 μm. The dimensions are given here for the first time since the original description in Rumrich et al. (2000) did not include them. Table 3 contains additional characteristics that are used below for comparative purposes in Discussion.

Figures

Figure 6. A-V LM images of little known and new " araphid " diatoms from the Bolivian Altiplano A-D Pseudostaurosira vulpina stat. nov. E-I P. frankenae sp. nov. (Fig. 6 E is the holotype) J-O P. occulta sp. nov. (Fig. 6 K corresponds to the holotype) P-V P. oblonga sp. nov. (Fig. 6 R corresponds to the holotype). Scale bar: 10 µm.

Figure 7. A-F SEM images of Pseudostaurosira vulpina sp. nov. A, B valve views showing striation pattern, features of the axial area, spine position and presence of depressed apical pore fields (black arrows) C, D close-ups with details of apical pore fields areolae and spines E tilted view of a frustule showing open girdle bands with overlapping extremes (white arrows) F internal view showing apical pore fields and the internal disk-like areolar depositions. Scale bars: 2 µm (C, D); 5 µm (A, B, E, F).