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

Figs 1T-Z (LM), 3A-F (SEM)

Holotype.

Slide ANSP GC 26815, Fig. 1U . 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. 3D ), joined together by interlocking spines (Figs 3C, F ). Valves narrowly lanceolate, isopolar, with abrupt transition from valve face to mantle. Rostrate valve ends in larger specimens, broadly rounded in smaller ones (Figs 1T-Z ). Axial area narrowly lanceolate (Figs 1T-Z , 3A, B ) and externally and internally depressed with respect to virgae (Fig. 3A, B ). Internally, striae open in small trapezoid, transapically elongated depressions (Fig. 3C ). Vimines short and wide, restricted to the valve face/mantle junction; additional ones rarely present on either valve face or valve mantle (Fig. 3C ). Striae typically composed by two narrow, round to elliptic areolae, one on valve face and a larger one on the valve mantle (Figs 3E, F ). Well-developed volae, arising from the areolar inner periphery and projecting inwards forming a loose mesh-like structure (Figs 3C, E ). Flaps usually present in various stages of development, typically single and disk-like on valve face and two or more on mantle areolae (Fig. 3A ). Spines originating from vimines at the valve face/mantle junction; solid, with round to elliptical base, wider that the vimines they sit on; flattened, with biconcave sides and spatulate body, truncated (cut) at the top or with a short bifurcation (Fig. 3A, B, D, E, F ). Stipules absent. Apical pore fields absent (Fig. 3C, E ). Well-developed blister-like depositions present on abvalvar edge of mantle also covering both apices (Fig. 3D-F ). Girdle elements variable in number, open, lacking pores, ligulated, with larger valvocopula (Fig. 3D, F ).

Dimensions (n> 50): Length 5-22 μm; width 2.4-3.0 μm; striae 13-16 in 10 μm.

Etymology.

The epithet makes reference to the neat and eye-catching morphology of the frustules.

Distribution.

Found in the Desaguadero and Sajama rivers.

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).