Further observations on Archaeosphaerodiniopsis verrucosa Rampi (Dinophyceae)

Abstract

The recently rediscovered dinoflagellate genus Archaeosphaerodiniopsis Rampi emend. Carbonell-Moore has been found in material from different oceans to that from where it was rediscovered. In all cases the cells were identified as Archaeosphaerodiniopsis verrucosa. Scanning electron microscopy (SEM) observations of these recently identified cells permitted completion of its description. It was confirmed that all large epithecal plates (1''–5'') have one large pore surrounded by a larger ring, except for plate 1'', which has two of these pores. Plates 2''' and 4''' lack the large pores, while the other postcingular plates and the antapical plate display the same large pore and ring. The relative position of this pore and ring on the plate was the same regardless of the geographic location where the cell was found. What was thought to be a growth band between the apical pore area and the first precingular plate was determined to be a very small separate plate, bringing the total number of apical plates to five. The number of cingular plates was confirmed to be six. All the cells of A. verrucosa observed to date, including Rampi’s, display well-developed intercalary bands, similar to those found in peridinioids, though with an overlapping plate pattern more typical of gonyaulacoids, where only the overlapping plate develops the growth band. The number of plates in the epitheca and the tabulation pattern closely resembles that of a typical gonyaulacoid (except the apical pore area), while its hypotheca is more of a peridinioid. The overlapping plate pattern matches that described in the literature for gonyaulacoids and peridinioids. A. verrucosa may be found in the Mediterranean, Central Equatorial Pacific, Coral Sea and Western Indian Ocean, in either surface or deep water. Plate tabulation formula: Po, Pt, X, 5', 6'', 6C, 4S, 5''', 1''''.