Symmetry and sex in Bacillariaceae (Bacillariophyta), with descriptions of three new Nitzschia species

They also agreed with these species in chloroplast morphology and auxosporulation and are therefore assigned to Nitzschia as N. dicrogramma, N. brachygramma and N. parkii, spp. nov . Consequently the only type of cell division found in all Hantzschia species (in which a hantzschioid parent cell divides to give two hantzschioid daughters) is not unique to Hantzschia but also occurs in at least one lineage of Nitzschia . ‘Core’ Hantzschia species may nevertheless comprise a monophyletic group, characterized by an unusual kind of internal central raphe endings.

Four symmetry categories are now known in Hantzschia and Nitzschia : (1) all cells hantzschioid; (2) hantzschioid and nitzschioid cells in a 2 : 1 ratio; (3) hantzschioid and nitzschioid cells in a 1 : 1 ratio; and (4) all cells nitzschioid. The division pattern seems to be constant within species and may therefore be useful as a taxonomic character above the species level. Hantzschia segmentalis is given its first written description.