Surirella Guide
Credit: Elizabeth Ruck
  1. Frustules isopolar or heteropolar
  2. Raphe positioned along entire valve margin
  3. Raphe located within a canal, which may be raised above valve surface

Cells of Surirella grow as single, isolated cells. The frustules may be either isopolar or heteropolar. Like other genera within the family Surirellaceae, the raphe system is positioned along the margin of the valve. The raphe is located within a canal, which may be raised above the valve surface in some species. Cells may be highly silicified, with spines and silica nodules on the valve surface.

Species in Surirella are common in the benthos, especially epipelic habitats, across a wide range of water chemistry. Cells may be relatively small, to very large (a few hundred micrometers), depending on the species. Because of the extensive raphe system, species of Surirella have high motility as compared to other diatom genera. They are able to live within sand grains and fine sediment, and can move through the sediment by means of the raphe system.

The genus Surirella was recently revised (Ruck et al. 2016). The phylogenetic relationships within the lineage were investigated in a number of works (Ruck and Kociolek 2005, Ruck and Theriot 2011, Ruck et al. 2016a, 2016b). In order for nomenclature to align with evolutionary relationships, a genus-level reclassification was published (Ruck et al. 2016). The genus Campylodiscus now includes the "fastuosoid" taxa of Surirella and Campylodiscus. Many of the marine Campylodiscus are now classified within the genus Coronia. The revised Surirella now includes the Surirella striatula clade, the Surirella Pinnatae group, and species formerly classified as Cymatopleura. Furthermore, the genus Iconella was resurrected to accommodate Stenopterobia and the "robustoid" taxa Surirella and Campylodiscus.