Morphology and molecular phylogeny of Ostreopsis cf. ovata and O. lenticularis (Dinophyceae) from Hainan Island, South China Sea

The genus Ostreopsis contains benthic and potentially toxic species that are distributed in tropical and temperate regions. In this study, we present the first report of observations of Ostreopsis cf. ovata and O. lenticularis in Chinese waters. Isolates were characterized morphologically based on LM and SEM, and phylogenetic analyses were conducted by sequencing the LSU rDNA (D1-D3), ITS region (ITS1-5.8S-ITS2) and SSU rDNA. The morphology of O. cf. ovata Hainan strains was similar to the original description of O. ovata, despite differences in cell size. The morphology of O. lenticularis Hainan strains was similar to the original description, although both deviations of cell dimensions and different kinds of thecal pores were observed. The plate formula for the Ostreopsis Hainan strains was arranged in Kofoid's system tabulation of Po, 30, 700, Vp, Rp, 1p, 5 ''', 2 ''''. The O. cf. ovata and O. lenticularis Hainan strains showed close relationships with strains collected from the Pacific Ocean based on the sequences of both LSU rDNA and ITS region. The genetic differences (p-distances) of SSU rDNA sequences of the Ostreopsis cf. ovata Hainan strain were 0.0096 and 0.0447 different from those of a Malaysian strain and a South Korean strain, respectively. This work identifies the first occurrence of Ostreopsis with the morphology and phylogeny of Hainan strains in Chinese waters.