Dinoflagellate Vulcanodinium rugosum identified as the causative organism of pinnatoxins in Australia, New Zealand and Japan

The producers of pinnatoxins E and F were first identified through systematic light microscopy-mass spectrometry (LC-MS) screening of New Zealand (NZ) dinoflagellate isolates. Pinnatoxins E, F and G were subsequently detected for South Australian (AUS) isolates, and a pinnatoxin G producer was recently identified from Okinawa, Japan. The NZ, AUS and Japanese isolates appear morphologically identical to Mediterranean field samples recently described as Vulcanodinium rugosum. Motile forms (24–32 μm long, 20–30 μm wide) have a wide, deeply incised cingulum displaced by 17% of the cell length and a deep sulcus. Photosynthetic motile cells have the same distinctive apical pore complex with raised collar and short canal plate. The reticulate thecal ornamentation resembles that of Bysmatrum because the three intercalary plates are connected. The posterior sulcal plate Sp does not touch the cingulum (as in Bysmatrum, Pentapharsodinium and Ensiculifera). The plate formula for the NZ, AUS and Japanese isolates is Po, X, 4', 3a, 7", 6c (5c + T), 5s, 5'", 2"". The dominant non-motile life-cycle stage comprises clusters of brown to black, spherical, unornamented, non-calcareous division cells (30–35 μm diameter). Genetically these isolates fall within the Peridiniales, closely related to the calciodinellid genera, Pentapharsodinium, Ensiculifera and Scrippsiella. The large subunit (LSU) rDNA and internal transcribed spacer (ITS) sequences exhibit sequence differences compared to each other and to the French field material (96–97% LSU and 84–88% ITS similarity, respectively). This variation and pinnatoxin profile differences suggest a possible species complex.