Mayamaea tytgatiana 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 : 43-45

Mayamaea tytgatiana Zidarova, Kopalová & Van de Vijver , sp. nov. ( Figs 59–80 )

LM observations ( Figs 59–76 ): Frustules in girdle view rectangular ( Fig. 76 ). Valves narrowly linear-lanceolate with weakly convex margins and gradually narrowing, slightly protracted, rounded to almost subrostrate apices. Valve dimensions (n=28): length 12.0– 15.0 μm, width 2.5–3.0 μm. Axial area very narrow, linear. Central area forming a bow-tie shaped, asymmetrical fascia, widening toward the margins. Raphe slightly curved with distinct, drop-like enlarged proximal endings, weakly deflected to one side. Distal raphe fissures barely visible in LM, hooked. Striae moderately radiate in the middle, becoming parallel and even weakly convergent toward the apices, 19–22 in 10 μm. Areolae not discernible in LM. SEM observations ( Figs 77–80 ): Striae composed of several rounded areolae, ca. 35 in 10 μm, covered externally by clearly porous hymenes ( Figs 77, 78 ).Areolae gradually becoming smaller on the valve mantle, usually rounded, rarely slit-like near the mantle edge ( Fig. 79 , arrows). At the apices mantle areolae often elongated ( Fig. 79 ). External raphe branches straight to weakly curved with distinctly enlarged, weakly unilaterally deflected proximal raphe endings ( Figs 77, 78 ). Distal raphe fissures elongated, hooked opposite to the proximal raphe endings, continuing onto the mantle ( Figs 77, 79 ). Internally, central nodule thickened ( Fig. 80 ). Internal raphe branches straight with simple proximal raphe endings ( Fig. 80 ). Distal raphe endings terminating onto small helictoglossae ( Fig. 80 ). Areolae clearly visible as rounded pores ( Fig. 80 ).

Type: — ANTARCTICA. South Shetland Islands: Deception Island, sample D37 (62° 59’ 25.5” S, 60° 37’ 31.7” W), R. Zidarova, 24 January 2013 (holotype BR! 4453, isotype PLP! 307).

FIGURES 46–58. Mayamaea sweetloveana sp. nov. LM & SEM pictures taken from the holotype population (sample D24) from James Ross Island. 46–56. LM views of 11 valves from the type population. 57. SEM of an entire valve, external view. 58. SEM of an entire valve, internal view. Scale bar represents 10 μm except for figs 57 and 58 where scale bar = 5 μm.

Etymology: —The specific epithet refers to Dr. Bjorn Tytgat (University of Ghent), member of the CCAMBIO project.

Ecology and confirmed distribution:— Mayamaea tytgatiana has up to now only been found in a few samples from Deception Island (South Shetland Islands). The largest population was observed on almost dry mosses growing in a small crack of a costal rock. The accompanying diatom flora included typically aerophilic diatom taxa, such as various Luticola and Humidophila species.

Family Neidiaceae

Genus Muelleria

Figures

FIGURES 59–80. Mayamaea tytgatiana sp. nov. LM & SEM pictures taken from the holotype population (sample D37) from Deception Island (South Shetland Islands). 59–76. LM views of 18 valves from the type population. Fig. 76 shows the girdle view. 77. SEM of an entire valve, external view. 78. SEM detail of the valve externally, showing the enlarged central raphe endings and rounded areolae with external hymenes. 79. SEM view of the valve mantle with the slit-like areolae (arrows) and the hooked, elongated distal raphe endings. 80. SEM of an entire valve, internal view. Scale bar represents 10 μm except for fig. 78 where scale bar = 1 μm and fig. 79 where scale bar = 2 μm.