Alexandrium minutum Halim, the generitype species of the toxigenic Alexandrium, was described from a 1958 bloom in the Eastern Harbor, Alexandria (Egypt) but has never been re-examined with modern methods from the type locality. Here we establish a monoclonal strain (TIO1796) by cyst germination from Alexandria’s port sediment and a second strain (TIO1816) from plankton samples from the Gulf of Suez. Cell morphology of both cultured strains and plankton samples was examined using scanning electron and light microscopy. The plate formula of A. minutum was identified as Po, *4ʹ, 6ʹʹ, 6C, 9S, 5ʹʹʹ, 2p, 1ʹʹʹʹ. Our results confirm the consistent presence of a ventral pore and a variable connection between Po and 1ʹ. Molecular phylogenetic analyses based on LSU rRNA and ITS region sequences reveal four ribotypes (A–D) of A. minutum. LSU and ITS sequences of both strains are identical and belong to the widespread ribotype A (“Global/Mediterranean clade”), whereas the other ribotypes are restricted to the Asia-Pacific region. Strain TIO1796 (type locality) is non-toxic (<0.024 pg cell⁻¹ PST), whereas TIO1816 produces GTX1/4-dominated toxins (0.48 pg cell⁻¹ total PST). These results (i) anchor the name A. minutum to ribotype A via neotypification of strain TIO1796, (ii) document the first PST-producing A. minutum in the Red Sea, and (iii) provide evidence supporting that A. minutum constitutes a cryptic species complex analogous to the A. tamarense species complex. The historical decline of A. minutum blooms in Alexandria since the 1990s correlates with near-absent cyst banks in recent sediments.
 

暂无