Taxonomic characterization of a brackish water, bloom-forming Peridiniopsis species (Peridiniales, Dinophyceae) from Iraq

Background The occurrence of a small brackish water bloom-forming dinoflagellate belonging to the genus Peridiniopsis is reported for the first time from the Shatt Al-Arab River in Iraq. Based on the study of cell morphology, this taxon was attributed to the recently described Peridiniopsis minima, recorded so far only from the Jiulongjiang River, China. Results The description of P. minima was extended to include some previously unreported details of the thecal surface, apical pore complex, and sulcus structure using light and scanning electron microscopy. Cells of this species from Iraq were oval to rhombic in shape and slightly dorso-ventrally compressed, with distinct red eyespot and endosymbiont nucleus. Cells were covered by a thin theca with the Kofoidian plate formula Po, X, 3′, 1a, 6″, 5c, 5 s, 5′′′, 2′′′′. Complementing the original description of the species, five plates were discerned in the composition of the sulcal area, and the presence of small median sulcal plate was confirmed. Conclusion The finding of P. minima in the waters of Shatt Al-Arab River represents a new addition to the Iraqi aquatic microflora. Our observations of this dinoflagellate in brackish waters of the Shatt Al-Arab River system extend the known range of salinity tolerance for this species