Mediolabrus

Mediolabrus is a genus of centric diatoms within the family Thalassiosiraceae. Known Mediolabrus species live planktonically in brackish and fresh water. This genus, together with the related Minidiscus, includes some of the smallest diatom species with diameters as small as 1.9 μm.

Taxonomy

Genus Mediolabrus was erected in 2020 based on molecular phylogenetics, by transferring three species from the genus Minidiscus.

Morphology and ultrastructure

The lenticular or spherical cells, smaller than 10 μm, live solitarily or in flocks. The valves are domed, with sloping mantle. The areolae are internally covered by individual, radially continuous cribra and lack typical foramens externally. At the edge of the valve face or close to the mantle are several fultoportulae. There is only one rimoportula and no fultoportulae in the center or sub-center of the valve. Only a single rimoportula near the valve center is a diagnostic feature of this genus and the source of its name.