Muelleria pimpireviana Zidarova, Kopalová & Van de Vijver, 2016

Zidarova, Ralitsa, Kopalová, Kateřina & Vijver, Bart Van De, 2016, Ten new Bacillariophyta species from James Ross Island and the South Shetland Islands (Maritime Antarctic Region), Phytotaxa 272 (1), pp. 37-62 : 46-48

Muelleria pimpireviana Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 81–91 )

LM observations ( Figs 81–89 ): Valves linear with broadly rounded apices. Larger and medium-sized valves with a distinct inflation in the middle ( Figs 81–88 ). Smallest valves with straight, non-inflated, parallel margins ( Fig. 89 ). Valve dimensions (n=17): length 18.3–47.5 μm, width 6.0–9.0 μm. Axial narrow, linear, widening in the valve center to form a small, elliptic central area. Raphe straight. Proximal raphe endings moderately distantly spaced, clearly unilaterally bent at an angle of approx. 90 degrees, long, extending to the first row of areolae. Distal raphe endings visible in largest valves, bifurcate ( Fig. 81 ). Striae near the central area (4–5 striae) more distantly spaced than the others, radiate, whereas other striae only slightly radiate, becoming parallel and denser toward the apices, finally parallel to very slightly convergent ( Figs 85, 86 ). Central striae 11–16 in 10 μm, distal striae 19–22 in 10 μm.Areolae coarse, 15–20 in 10 μm. SEM observations ( Figs 90–91 ): Striae composed of rounded to slightly transapically elongated areolae of almost equal size ( Fig. 90 ). Proximal raphe endings clearly unilaterally bent, extending up to, or into, but never beyond the first row of areolae ( Fig. 90 ). Distal raphe endings straight, clearly bifurcate, terminating shortly onto the valve face just before the valve face/valve mantle junction ( Fig. 91 ). Striae continuing curving around the distal raphe endings and onto the mantle ( Fig. 91 ). Canal punctae never observed ( Figs 90, 91 ). Due to the rarity of the species in the samples, observations on the valve interior could not be made.

Type: — ANTARCTICA. South Shetland Islands: Nelson Island, sample NI 26 (62° 14’ 10.1” S, 59° 00’ 05.6” W), R. Zidarova, 20 February 2013 (holotype BR! 4454, isotype PLP! 308).

Etymology: —The species is named after Prof. Dr. Christo Pimpirev (Bulgarian Antarctic Institute), a leader of 24 Bulgarian Antarctic expeditions, to acknowledge his personal long-term dedication to Antarctica, and without whom Bulgarian scientific campaigns on the South Shetland Islands would not have been possible.

Ecology and confirmed distribution: — Muelleria pimpireviana has been rarely observed on several islands of the South Shetland Archipelago (Nelson Island, King George Island and Livingston Island). The largest population was found in a moist, circumneutral (pH 7.1) soil at the base of a coastal rock on Nelson Island. The accompanying diatom flora included several other Muelleria species and various Luticola and Pinnularia taxa. Occasionally, the species was also observed on wet terrestrial mosses and on the bottom of a shallow pool.

Family Naviculaceae

Genus Navicula

Figures

FIGURES 81–91. Muelleria pimpireviana sp. nov. LM & SEM pictures taken from the holotype population (sample NI26) from Nelson Island (South Shetland Islands). 81–89. LM views of 9 valves from the type population. 90. SEM of the valve exterior. 91. SEM detail of the apex, showing the bifurcated distal raphe endings. Scale bar represents 10 μm except for fig. 91 where scale bar = 2 μm.