Light and electron microscopical observations on Protoceratium reficulatum (Dinophyceae)

Light and electron microscopical observations have been made on the gonyaulacoid dinoflagellate Protoceratium reficulatum (Claparède et Lachmann) Bütschli collected close to the type locality of Protoceratium acerosBergh, the type species of Protoceratium. Analysis of plate tabulation shows agreement with Gonyaulax grindleyiREINECKE and supports conspecificity between P. reticulatum, P. aceros and G. grindleyi, the first name having priority. The ultrastructure includes a branched chloroplast and a centrally located pyrenoid complex. The pusular system consists of one or two sac pusules associated with the flagellar canals. The three-dimensional arrangement of the flagellar apparatus is basically similar to that of other dinoflagellates except for the presence of a single microtubular root associated with the longitudinal basal body. Each flagellar canal is surrounded by a distinct striated fibrous collar. The collars are interconnected by two striated connectives. The plate tabulation and fine structure of Protoceratium reficulatum indicate close relationship to the genus Gonyaulax, with minor differences in plate tabulation and fine structure. It is suggested to maintain the genus Protoceratium until the fine structural diversity with Gonyaulax is better known.