<i>Karlodinium australe</i>sp. nov. (Gymnodiniales, Dinophyceae), a new potentially ichthyotoxic unarmoured dinoflagellate from lagoonal habitats of south-eastern Australia

A new species in the toxigenic genus Karlodinium, K. australe de Salas, Bolch &amp; Hallegraeff sp. nov., is described from coastal lagoons and enclosed bay habitats in Tasmania and south-eastern Australia. This mixotrophic species is characterised with the use of light and electron microscopy, pigment analysis and sequencing of the large subunit ribosomal gene from field samples and laboratory cultures. Karlodinium australe has a straight, short apical groove and a ventral pore typical of the genus, but is almost twice the size (19-26 m long) of other species in the genus. It is morphologically similar to Gyrodinium corsicum and Karenia digitata but has an anteriorly located nucleus and a different amphiesmal pattern. Karlodinium australe has a partial large subunit ribosomal gene (26S ribosomal DNA) sequence that differs by 7.2% from that of K. micrum, and its pigment profile does not include gyroxanthin-diester. Unlike the type species of the genus, K. micrum, K. australe has no detectable hexagonal array of plug-like structures below the amphiesma, and its chloroplasts contain pyramidal rather than lenticular pyrenoids.