Pseudostaurosira aedes E. Morales, C.E. Wetzel & Ector, 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 aedes E. Morales, C.E. Wetzel & Ector sp. nov.

Figs 1A ’-G’ (LM), 4A-F (SEM)

Holotype.

Slide ANSP GC 26815, Fig. 1A ', Diatom Herbarium, Academy of Natural Sciences, Philadelphia (ANSP). Isotype. Slide DBOL-0246a, Diatomotheca Boliviensis (before HCUCB), Cochabamba, Bolivia.

Type locality.

Bolivia. Sajama Province, Department of Oruro, Desaguadero River, epipsammon, 17°23'51"S; 68°14'33"W, 3701 m elev., leg. G. Chávez, 05.07.2009.

Description.

Frustules rectangular in girdle view (Fig. 4B, D-F ), joined together by interlocking spines (Fig. 4F ). Valves narrowly elliptic with rounded ends, isopolar, with abrupt transition from valve face to mantle (Fig. 1A ’-G’). Axial area narrowly lanceolate (Figs 1A ’-G’, 4A, B, D), externally only slightly below the virga (Fig. 3A, D, E ). Internally, axial area and virgae raised, leaving the striae in large elliptic or 8-shaped, transapically elongated depressions (Fig. 4C ). Vimines shorter than virgae and wide, restricted to the valve face/mantle junction; additional ones rarely present on valve mantle (Fig. 4B ). Striae typically composed by two narrow, elliptic to trapezoid areolae, one on valve face and a slightly larger one on the valve mantle (Fig. 4A, B, D, E ). Volae arising from the areolar inner periphery and projecting inwards forming a tightly packed mesh-like structure (Fig. 4B, C ). Flaps frequently present in various stages of development, typically one disk-like or bilobate on valve face and two or more of different shape on valve mantle areola (Fig. 4A, B, D-F ). Spines originating from vimines at the valve face/mantle junction, solid, with elliptic to rectangular base, as wide as the vimines; conical body with a roughly triangular profile and serrate, pointy tips. Spines have a general arrowhead-like appearance when seen form their posterior ends. (Fig. 4A-F ). Stipules well-developed giving spines a sagittate shape and having themselves varying shapes in girdle view (Fig. 4D-F ). Apical pore fields very reduced with no more than 3 round poroids, usually externally obliterated by an apical blister (Fig. 4C, D, E ). Well-developed blister-like depositions present on abvalvar edge of mantle (Fig. 4B-F ). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 4B, D-F ).

Dimensions (n> 50): Length 2.9-12.3 μm; width 2.1-2.3 μm; striae 15 in 10 μm.

Etymology.

The species epithet makes reference to the difficulty in the LM distinction of this diatom from co-occurring species with similar outline.

Distribution.

Found in the Desaguadero River.

Figures

Figure 1. A-M ' LM images of little known and new " araphid " diatoms from the Bolivian Altiplano A-E Nanofrustulum cataractarum F-L N. rarissimum M-S Pseudostaurosira sajamaensis T-Z P. pulchra sp. nov. (Fig. 1 U is the holotype) A' - G ' P. aedes sp. nov. (Fig. 1 A ' is the holotype). H' - M ' P. heteropolaris sp. nov. (Fig. 1 I ' is the holotype). Scale bar: 10 µm.

Figure 3. A-F SEM micrographs of Pseudostaurosira pulchra sp. nov. from the Bolivian Altiplano A, B outer views of valves showing axial area, striae and spines features C inner view of valve still attached to neighboring cell. Black arrow indicates absence of apical pore field. Dotted arrow points to depression into which the stria opens internally D tilted view of frustule. Notice larger valvocopula, lateral growth of spines and blister-like depositions on abvalvar edge of mantle E outer view of valve tip. Black arrow denotes absence of apical pore field. Notice round to elliptical spine base and larger areola on valve mantle. F frustule attached to neighboring valve by means of heavily silicified spines. Notice open girdle elements (white arrow) and depositions along abvalvar mantle edge. Scale bars: 2 µm (E); 4 µm (C, F); 5 µm (A, B, D).

Figure 4. A-F SEM images of Pseudostaurosira aedes sp. nov. from the Bolivian Altiplano A top, tilted view of valve showing axial area, slightly raised virga, valve face areolae covered with bilobed or disk-like flaps, and slightly larger valve mantle areola covered with two or more flaps B, D, E, F girdle views showing features of the valve mantle, open girdle elements with larger valvocopula (white arrows in D and E). Notice serrate spines with well-developed stipules in F which have varying patterns C inner view showing reduced apical pore field (black arrow) and single depression into which the areolae open internally (dotted arrow). Scale bars: 4 µm (D); 5 µm (A-C, E, F).