Guide to Licmophora

Species in the genus Licmophora are found in marine habitats, from polar to tropical regions. Cells grow singly or in colonies on branching, mucilaginous stalks attached to various substrates such as seaweeds, rocks, and act to "biofoul" structures such as docks and the hulls of boats.

Frustules are heteropolar, with a narrow base and broader apex. In girdle view, frustules are cuneate. Striae are uniseriate and are usually parallel, except around apices. Frustules are heterovalvar inasmuch as a rimoportula is present on one valve at the base and on the other valve, or both valves, at the apex. A multiscissura, series of slits, is present around the base of both valves. Plastids are usually small and numerous.

The epicingula and mature hypocingula each comprise five distinct girdle bands. Valvocopulae are open at the base and may possess a septum at the apex. Four pleurae are open at alternate ends.

Ultrastructural features of the frustule include number, size, and location of the apical rimoportulae, characteristics of the areolae, number of slits in the multiscissura, and details of girdle bands, especially the septum and midrib path on the valvocopula and the character of the fourth pleura (Honeywill 1998, Lobban et al. 2018).

The genus is distinguished from Podocystis by the striae; Licmophora has uniseriate striae, while Podocystis has biseriate or multiseriate striae. Species identification of Licmophora by light microscopy can be difficult, especially for delicate or hyaline species.

The genus currently has over 100 taxa, including taxa with apical "windows" in the septa, which were formerly in Licmosphenia Mereschk. 1902 (Lobban et al. 2015).