SPECIES OF THE TOXIGENIC DINOFLAGELLATE GENUS ALEXANDRIUM IN SOUTHEASTERN AUSTRALIAN WATERS

Five species of the toxigenic, marine dinoflagellate genus Alexandrium are reported from south-eastern Australian waters: A. minutum Halim, A. catenella (Whedon et Kofoid) Balech, A. tamarense (Lebour) Balech, A. affine (Fukuyo et Inoue) Balech and a new species to be described as A. margalefi in Balech's monograph on the genus Alexandrium. Production of paralytic shellfish poisons was confirmed for A. minutum and A. catenella, but isolates of A. margalefi, A. tamarense and A. affine were non-toxic. All the species produce smooth-walled, mucilaginous resting cysts but these ranged in shape from spherical (A. margalefi, A. affine), hemispherical (A. minutum) to cylindrical with rounded ends (A. catenella, A. tamarense). Considerable variation in the cell shape of wild and cultured populations is documented for A. margalefi, A. catenella and A. affine. However, details of shape of the first apical plate (with or without ventral pore), the apical pore complex (with anterior attachment pore) and the posterior sulcal plate (with posterior attachment pore) proved to be conservative taxonomic characters. Historic reports of PSP toxins (Batemans Bay 1935) and of a chain-forming gonyaulacoid dinoflagellate (Gonyaulax conjuncta Wood) in New South Wales waters are reviewed. The species A. margalefi, A. tamarense and A. affine are new records for the Australian region.