Hygroptera Guide
Credit: Loren Bahls, Pat Kociolek
  1. Striae broad
  2. Striae alveolate
  3. Robust transapical costae

The species in Hygropetra are small in size, with broad, V-shaped striae. The striae are alveolate, or composed of very small pores, in rows of 3-4. A small septum is present. Internally, robust transapical costae are positioned between the striae. The raphe is filiform, with a relatively large gap between proximal raphe ends.

Hygropetra is a genus of small taxa previously considered within Pinnularia. The group is typical of low nutrient, northern temperate and arctic lakes and mosses.