Morphological, phylogenetic and metabolite profile of Prorocentrum clipeus, a newly recorded epiphytic dinoflagellate in the northern Yellow Sea

More than 30 species of benthic Prorocentrum have been identified, some of which produce okadaic acid (OA) and its derivatives, dinophysistoxins (DTXs), which cause diarrhetic shellfish poisoning (DSP). Increasing numbers of benthic Prorocentrum species have been reported in tropical and subtropical waters of China. In contrast, only a few benthic Prorocentrum species have been reported in temperate waters. In this study, morphological descriptions obtained using light microscopy, scanning electron microscopy and molecular characterization of one Prorocentrum clipeus strain isolated from the Yellow Sea are presented. Prorocentrum clipeus cells were nearly circular in shape, with a collar, ridge, and one protrusion. The periflagellar area was wide U-shaped, with two curved projections on platelet 1a. Nine periflagellar platelets of different sizes were observed. The morphology closely fits that of the species isolated from other locations. Phylogenetic analysis based on the molecular sequences of the small subunit (SSU) rDNA, internal transcribed spacer (ITS), and large subunit (LSU) rDNA was performed. A comprehensive metabolomic analysis incorporating target, suspect and non-target screenings was first applied to investigate the intracellular and extracellular metabolite profiles of the current isolate of P. clipeus . According to the results of the target and suspect screenings, 179 metabolites or toxins produced by DSP-related algal species, including OA, dinophysistoxin-1 (DTX1), dinophysistoxin-2 (DTX2) and pectenotoxin-2 (PTX2), were not detected. Non-target screening involving feature-based molecular networking (FBMN) provided a global view of major metabolites produced by the P. clipeus DF128 strain and revealed 23 clusters belonging to at least 13 compound classes, with organometallic compounds, lipids and lipid-like molecules, phenylpropanoids and polyketides, and benzenoids as major types. To date, this is the first record of the characterization of P. clipeus in samples from Chinese waters. Our results support the wide distribution of epibenthic Prorocentrum species.