A Mediterranean Alexandrium taylorii (Dinophyceae) strain produces goniodomin A and lytic compounds but not paralytic shellfish toxins

Species of the dinophyte genus Alexandrium are widely distributed and are notorious bloom formers and producers of various potent phycotoxins. The species Alexandrium taylorii is known to form recurrent and dense blooms in the Mediterranean, but its toxin production potential is poorly studied. Here we investigated toxin production potential of a Mediterranean A. taylorii clonal strain by combining state-of-the-art screening for various toxins known to be produced within Alexandrium with a sound morphological and molecular designation of the studied strain. As shown by a detailed thecal plate analysis, morphology of the A. taylorii strain AY7T from the Adriatic Sea conformed with the original species description. Moreover, newly obtained Large Subunit (LSU) and Internal Transcribed Spacers (ITS) rDNA sequences perfectly matched with the majority of other Mediterranean A. taylorii strains from the databases. Based on both ion pair chromatography coupled to post-column derivatization and fluorescence detection (LC-FLD) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis it is shown that A. taylorii AY7T does not produce paralytic shellfish toxins (PST) above a detection limit of ca. 1 fg cell−1, and also lacks any traces of spirolides and gymnodimines. The strain caused cell lysis of protistan species due to poorly characterized lytic compounds, with a density of 185 cells mL−1 causing 50% cell lysis of cryptophyte bioassay target cells (EC50). As shown here for the first time A. taylorii AY7T produced goniodomin A (GDA) at a cellular level of 11.7 pg cell−1. This first report of goniodomin (GD) production of A. taylorii supports the close evolutionary relationship of A. taylorii to other identified GD-producing Alexandrium species. As GD have been causatively linked to fish kills, future studies of Mediterranean A. taylorii blooms should include analysis of GD and should draw attention to potential links to fish kills or other environmental damage.