Cytological characteristics of the Sellaphoraceae

Abstract

Chloroplast and pyrenoid structure are described for Sellaphora, Fallacia and Rossia (Sellaphoraceae). All have a single chloroplast per cell, which is basically H-shaped, consisting of two large girdle-appressed plates connected by a central isthmus, though the plates may also bear longitudinal or transverse lobes; one or two invaginated pyrenoids are always present. Fallacia chloroplasts are more variable than those of Sellaphora but always differ fundamentally from the valve-appressed chloroplasts of the unrelated but superficially similar genus Lyrella. Outside Sellaphoraceae, invaginated pyrenoids are uncommon except in the Pinnulariaceae, closely related to the Sellaphoraceae according
to molecular data and sharing a similar raphe structure, consistent with the classification of both in the suborder Sellaphorineae. However, invaginated pyrenoids are also found in Diploneis.