Humidophila contenta (Grunow) R.L. Lowe et al.

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 : 31-32

Humidophila contenta (Grunow) R.L. Lowe et al. ( Figs 18–38 )

Morphological observations:—Smaller specimens elliptical with parallel margins, larger specimens linear, usually with concave margins and broadly rounded, never (sub-)capitate ends.Valve dimensions (n=25): length 6.1 – 11.6 μm, width 2.1–2.9 μm. Axial area narrow, linear. Central fascia clearly present, extending from the central nodule to the valve margins. Raphe filiform, straight with distinct T-shaped central and terminal endings. Transapical striae parallel, interrupted centrally, fine, difficult to resolve in LM, 34 – 49 in 10 μm. Mantle areolae rounded to elongated, continuing around the apices without an interruption. Girdle composed of three copulae, perforated by a series of transapically elongated slits.

Ecology and associated diatom flora:—Based on valve morphology, Humidophila contenta is one of the few cosmopolitan species of this genus. It has been reported worldwide in soils, subaerial habitats, in small bodies of oligotrophic acidic water and in biotopes with greatly reduced light intensity ( Werum & Lange-Bertalot 2004, Poulíčková & Hašler 2007). On Ile Amsterdam and Ile Saint Paul H. contenta has been found living on moss species of the genus Anthoceros L., Brachythecium Schimp. and Sphagnum L. showing a specific moisture value ranging from F-V to F-VII, and in soils, usually accompanied by Humidophila vidalii , H. amsterdamensis sp.nov., Eunotia muscicola Krasske (1939: 366) , Pinnularia borealis Ehrenberg (1843b: 420) s.l., Pinnularia perminor Kulikovskiy, Lange-Bertalot & Metzeltin (2010: 359) , Luticola beyensii and Tryblionella debilis Arnott ex O’Meara (1873: 310) .

Figures

FIGURES 18–38. Humidophila contenta (Grunow) R.L.Lowe et al. Light (LM) and scanning electron micrographs (SEM). 18–19. LM of a girdle view. 20–34. LM of valve views showing variation in size. 35. SEM of an entire valve (externally). 36. SEM of a girdle view. 37–38. SEM of an entire valve (externally). Note the proximal and distal raphe endings showing small depressions next to the raphe pores. LM scale bar = 10 μm. SEM scale bars = 1 μm.