Lowe et al. 2014      Category: Symmetrical biraphid
TYPE SPECIES: Humidophila undulata Lowe, Kociolek and Johansen




Image Credit: Rex Lowe, Marina Potapova, Sarah Spaulding

CLASS: Bacillariophyceae
  ORDER: Naviculales
    FAMILY: Diadesmidaceae

  1. Striae composed of single elongate areola
  2. External raphe ends curved or T-shaped

Valves are small, usually less than 20 µm. Valves are linear, linear-elliptical to elliptical. The apices are broadly rounded. The central nodule is small and rounded.

Other features of Humidophila are visible under SEM. The valve face is flat, and may have a narrow rim, or ridge, differentiating the valve face from the mantle. Striae on the valve face are composed of one usually transapically elongated, elliptical to ovoid areola. In some species, mantle areolae located on the valve face give the impression of two valve face areolae per stria. On the valve mantle, one single, elongated areola opening extending the width of the mantle present in line with each stria,. Near the valve apices, slit-like areolae sometimes present on the mantle, occasionally interrupted at the apices. The raphe may be secondarily filled with silica. When present, the raphe is filiform and straight. The external proximal raphe ends are simple, drop-like or anchor-shaped. The proximal ends are never deflected, bent or hooked. The distal external raphe ends are similarly shaped. The distal ends never extend onto the mantle. Internally, the areolae are covered by a porous hymen. Proximal raphe ends are straight or slightly anchor-shaped, while the distal raphe ends terminate in small helictoglossae.

The genus Humidophila is most abundant in aerial or subaerial habitats, and the genus is particularly diverse in the Antarctic and sub-Antarctic. Cosmopolitan taxa include H. contenta (Grunow ex Van Heurck) Lowe et al. and H. paracontenta (Lange-Bertalot and Werum) Lowe et al. The genus includes 47 species formerly included in Diadesmis.

Cite This Page:
Lowe, R. (2014). Humidophila. In Diatoms of the United States. Retrieved March 25, 2017, from

Contributor: Rex Lowe - December 2014