Navicula romanedwardii 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 : 48

Navicula romanedwardii Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 92–98, 104–118 )

LM observations ( Figs 92–98, 104–114 ): Frustules in girdle view rectangular ( Fig. 92 ). Valves lanceolate to rhombic-lancoleolate (e. g., Figs 96, 97 ). Margins usually clearly convex. Valve apices acutely rounded, never protracted. Valve dimesions (n=20): length 23–29 μm, width 5.5–7.0 μm. Axial area narrow, widening towards the central area. Central area rather small, rhombic, widening towards the margins. Single shortened stria present on each side of the central area. Raphe filiform, straight. Proximal raphe endings deflected, terminating in distinctly drop-like pores. Distal fissures hooked towards the secondary side. Striae in the valve middle strongly radiate, becoming parallel to weakly convergent near the apices, 8–10 in 10 μm. Areolae discernible in LM. SEM observations ( Figs 115–118 ): Striae composed of small lineolae, ca. 35 in 10 μm ( Fig. 115 ). Striae narrower than the virgae ( Figs 115, 116 ). At each valve apex, one transapically positioned slit present next to the distal raphe fissures ( Fig. 115 , arrows). External raphe branches situated on a thickened, raised sternum ( Fig. 115 ). Proximal raphe endings drop-like expanded ( Fig. 115 ). Distal raphe fissures elongated, continuing onto the mantle and finishing at the valve poles below the slits ( Fig. 115 ). Internally, areolae situated in transapically running grooves ( Fig. 118 ). Areolae occluded by individual hymenes ( Fig. 117 ). Raphe running laterally on a distinctly developed raphe sternum, continuing near the well developed, apically elongated central nodule ( Fig. 118 ). Internal distal raphe endings terminating shortly onto small helictoglossae ( Fig. 117 ).

Type: — ANTARCTICA. James Ross Island: soil near Muddy Lake, sample JRI-D18 (63° 51’ 50.1” S, 57° 57’ 12.2” W), L. Nedbalová, 1 February 2008 (holotype BR! 4455, isotype PLP! 309).

Etymology: —The species is named after Mr. Roman Edward, a sailor and zodiac boat driver during several Bulgarian Antarctic expeditions, in recognition of his help in the scientific activities on Livingston Island.

Ecology and confirmed distribution: — Navicula romanedwardii is a widely distributed species in Maritime Antarctica, observed on all major islands of the South Shetland Archipelago and on James Ross Island. The species had also been recorded on the Antarctic continent (see Van de Vijver et al. 2011b). On James Ross Island, the largest populations were found in the epipelon and epilithon of larger lakes, having an almost circumneutral to slightly alkaline pH (6.8–7.6), moderate to high specific conductance values (100–200 μS/cm) and moderate nutrient values (TP 46–592 μg/L), together with various Nitzschia species. On the South Shetland Islands Navicula romanedwardii was observed in a variety of habitats, ranging from small pools and streams to moss vegetation cover and soils, but usually in low abundances. A large population was found on Deception Island (South Shetland Islands) on almost dry mosses. Occasionally, the species was also observed in seepage areas.

Family Pinnulariaceae

Genus Pinnularia

Figures

FIGURES 92–118. Navicula romanedwardii sp. nov. and Navicula seibigiana s.s. LM & SEM pictures of Navicula romanedwardii taken from the holotype population (sample D18) from James Ross Island and two other populations on James Ross Island and South Shetland Islands (indicated below). LM pictures of Navicula seibigiana taken from the type slide (Praep. Hintz 160, Eu-CH 15 in Coll. Lange- Bertalot). 92–98. Navicula romanedwardii, LM views of 7 valves from the type population. Fig. 92 shows the girdle view in LM. 99–103. Navicula seibigiana s.s., LM views of 5 valves from the type population. 104–114. Navicula romanedwardii, LM views of 11 valves from a Deception Island population (sample D37). 115. Navicula romanedwardii, SEM of an entire valve, external view.Arrows show the slits at the apices. 116. Navicula romanedwardii, SEM detail of the central area and central raphe endings. 117. Navicula romanedwardii, SEM of an entire valve, internal view (picture taken from James Ross Island, sample JRI015). 118. Navicula romanedwardii, SEM detail of the central part of the valve internally, showing the continuous raphe (picture taken from James Ross Island, sample JRI015). Scale bar represents 10 μm except for figs 116 and 118 where scale bar = 1 μm.