First reports of P seudo‐nitzschia micropora and P . hasleana ( B acillariaceae) from the S outhern H emisphere: Morphological, molecular and toxicological characterization

Summary P seudo‐nitzschia   H . P eragallo is a marine diatom genus found worldwide in polar, temperate, subtropical and tropical waters. It includes toxigenic representatives that produce domoic acid ( DA ), a neurotoxin responsible for A mnesic S hellfish P oisoning. In this study we characterized two species of P seudo‐nitzschia collected from P ort S tephens and the H awkesbury R iver (south eastern A ustralia) previously unreported from A ustralian waters. Clonal isolates were sub‐sampled for (i) light and transmission electron microscopy; (ii) DNA sequencing, based on the nuclear‐encoded partial large subunit ribosomal RNA gene and internal transcribed spacer ( ITS) ‐ ITS1 , 5.8S and ITS2 rDNA regions and, (iii) DA production as measured by liquid chromatography‐mass spectrometry. Morphological and molecular data unambiguously revealed the species to be P seudo‐nitzschia micropora   P riisholm, M oestrup & L undholm ( P ort S tephens) and P seudo‐nitzschia hasleana   L undholm ( H awkesbury R iver). This is the first report of the occurrence of these species from the S outhern H emisphere and the first report of P . micropora in warm‐temperate waters. Cultures of P . micropora , tested for DA production for the first time, proved to be non‐toxic. Similarly, no detectable toxin concentrations were observed for P . hasleana . Species resolution and knowledge on the toxicity of local P seudo‐nitzschia species has important implications for harmful algal bloom monitoring and management.