Humidophila amsterdamensis Chattová &Van de Vijver, 2018

Chattová, Barbora, Lebouvier, Marc & Vijver, Bart Van De, 2018, Morphological and taxonomical analysis of the terrestrial diatom genus Humidophila (Bacillariophyta) on Ile Amsterdam and Ile Saint-Paul (Southern Indian Ocean), Phytotaxa 336 (1), pp. 28-42 : 34-36

Humidophila amsterdamensis Chattová &Van de Vijver sp. nov. ( Figs 101–121 )

Light microscopy ( Figs 101–115 ): Valves linear with gibbous central part and broadly rounded, non-protracted apices. Valve dimensions (n = 50): length 13.5–32.5 μm, width 3–5.5 μm. Axial area linear, fairly wide. Central area round, slightly widened due to the shortening of the central striae, never forming a fascia. Raphe filiform, straight with simple straight proximal and distal endings. Striae parallel throughout the entire valve, not interrupted in the middle.

SEM ( Figs 116–121 ): Striae parallel, composed of one short, transapically elongated areola ( Fig. 116 ), not interrupted near the proximal raphe pores, but curving around the central nodule, 31–32 in 10 μm. In smaller specimens, striae near the apices terminating near the distal raphe endings ( Fig. 118 ). In larger specimens striae terminating beyond the distal raphe endings ( Fig. 117 ). Raphe filiform with weakly expanded proximal and straight distal pores. Mantle areolae enlarged, positioned in a longitudinal groove running from one apex to the other ( Fig. 119 ). Grooves disappearing near the apices, revealing areolae on the mantle. Mantle areolae becoming smaller and rounded near the apices, continuing around the apices usually without or with a small interruption ( Fig. 121 ). External raphe branches straight with simple proximal endings. T-shaped distal and proximal endings never observed. Distal raphe endings short, terminating on the valve face, well before the apices, never exceeding on the valve mantle ( Figs 118 and 121 ). Internally ( Fig. 120 ), areolae appearing much larger than externally, occluded by porous hymens. Well-developed central nodule present. Internal raphe endings straight with distal endings terminating on very weakly developed helictoglossae. Girdle composed of three open copulae, perforated by two rows of very small rounded poroids ( Fig. 119 ). Poroids in the second row more widely spaced.

Type:— ILE AMSTERDAM, TAAF sample AMS-M035, B. Van de Vijver , 4 December 2007 (holotype: BR! slide no. 4488; isotype: PLP! slide no. 326, University of Antwerp, Belgium). The holotype specimen is represented by Fig. 101 .

Etymology:—The specific epithet refers to the type location, Ile Amsterdam.

Ecology and associated diatom flora:— Humidophila amsterdamensis was found in a sample taken from semi-dry mosses with F-value VI, taken from a small cave bog-pond with a pH of 6.1 and a conductivity value of 220 μS cm- 1. The sample was dominated by Eunotia lecohui Van de Vijver (in Van de Vijver et al. 2008: 117), Chamaepinnularia aerophila Van de Vijver & Beyens (in Van de Vijver et al. 2002a: 26), Microfissurata australis Van de Vijver & Lange-Bertalot , Orthoseira verleyenii and Pinnularia amsterdamensis Chattová et al. (in Van de Vijver et al. 2012: 217). The species was not observed on Ile Saint Paul.

Figures

FIGURES 101–121. Humidophila amsterdamensis Chattová &Van de Vijver sp. nov. Light (LM) and scanning electron micrographs (SEM). 101–115. LM of valve views of the type population from Ile Amsterdam. 116–118. SEM of an entire valve (externally). 119. SEM of a girdle view. 120. SEM of internal valve view. 121. SEM of an entire valve (externally). LM scale bar = 10 μm. SEM scale bars = 5 μm.