Humidophila gallica (W.Smith) R.L.Lowe et al., 2017

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 : 33

Humidophila gallica (W.Smith) R.L.Lowe et al. ( Figs 60–79 )

Morphological observations:—Frustules are rectangular in girdle view, usually forming long, bandlike colonies, connected by linking spines. Valves are linear-elliptical with bluntly rounded, rarely subcapitate apices. Valve dimensions (n=25): length 8–11.5 μm, width 1.9 – 3.2 μm. Two contrasting valves morphologies are observed. Most valves lacking a raphe system but are showing well-developed marginal spines. Occasionally valves with a normally developed raphe system lacking marginal spines were observed. Striae are not discernible in LM, 34 – 42 in 10 μm, composed (SEM) of one large, transapically elongated areola.

Ecology and associated diatom flora: — Humidophila gallica is a cosmopolitan species, common in terrestrial biotopes such as bryophyte vegetations, wet to semi-dry rock faces, soils and in caves ( Falasco et al. 2014, 2015, Lowe et al. 2017). On Ile Amsterdam, this species was found in high abundance in lava tubes, accompanied by other Humidophila species (mainly H. vidalii and H. contenta ), Rhopalodia rupestris (W. Smith 1853: 14) Krammer in Lange-Bertalot & Krammer (1987: 86) and Orthoseira roeseana ( Rabenhorst 1848 –1860: 383) O’Meara (1875: 255).

Figures

FIGURES 60–79. Humidophila gallica (W.Smith) R.L. Lowe et al. Light (LM) and scanning electron micrographs (SEM). 60. LM of a girdle view of two frustules, connected by linking spines. 61–75. LM of valve face views. 76. SEM of an entire valve (externally). 77. SEM valve (internally). 78. SEM valve (internally) and SEM of a valve with marginal spines (externally). 79. SEM of an entire valve (externally). LM scale bar = 10 μm. SEM scale bars = 1 μm.