Plate pattern variability and plate overlap in a clonal culture of the freshwater dinoflagellate Peridinium umbonatum STEIN species complex (Dinophyceae)

In a clonal culture of a freshwater dinoflagellate belonging to the Peridin ium umbonatum STEIN species complex, plate pattern variability and plate ov erlap pattern were investigated and documented by scanning electron microsc opy. In addition, various field populations were investigated. All possible plate pattern variations of the dorsal epitheca: tabulatio (tab.) conjunct um, tab. contactum and tab. remotum were observed in clonal culture and fie ld material. In the clonal culture investigated, 94% of the cells showed th e tab. conjunctum, 4% the tab. contactum and 2% the tab. remotum. Other pla te patterns were also observed. In field populations, also only one tabulat ion type was dominant. Plate overlap pattern is depicted in diagrams for th e tabulation varieties of Peridinium umbonatum. The plate overlap-pattern w as always constant, no flip-flop of the overlap between the two apical inte rcalary plates in tab. remotum was observed as could be expected.