Diversity and toxicity of Pacific strains of the benthic dinoflagellate Coolia (Dinophyceae), with a look at the Coolia canariensis species complex

Bacterial communities and toxin profiles of Ostreopsis (Dinophyceae) from the Pacific Island of Okinawa, Japan

Variations in toxicity of the benthic dinoflagellate Ostreopsis Schmidt 1901 have been attributed to specific molecular clades, biogeography of isolated strains, and the associated bacterial community. Here, we attempted to better understand the biodiversity and the basic biology influencing toxin production of Ostreopsis. Nine clonal cultures were established from Okinawa, Japan, and identified using phylogenetic analysis of the ITS-5.8S rRNA and 28S rRNA genes. Morphological analysis suggests that the apical pore complex L/W ratio could be a feature for differentiating Ostreopsis sp. 2 from the O. ovata species complex. We analyzed the toxicity and bacterial communities using liquid chromatography-mass spectrometry, and PCR-free metagenomic sequencing. Ovatoxin was detected in three of the seven strains of O. cf. ovata extracts, highlighting intraspecies variation in toxin production. Additionally, two new potential analogs of ovatoxin-a and ostreocin-A were identified. Commonly associated bacteria clades of Ostreopsis were identified from the established cultures. While some of these bacteria groups may be common to Ostreopsis (Rhodobacterales, Flavobacteria-Sphingobacteria, and Enterobacterales), it was not clear from our analysis if any one or more of these plays a role in toxin biosynthesis. Further examination of biosynthetic pathways in metagenomic data and additional experiments isolating specific bacteria from Ostreopsis would aid these efforts.

Ostreopsis Schmidt and Coolia Meunier (Dinophyceae, Gonyaulacales) from Cook Islands and Niue (South Pacific Ocean), including description of Ostreopsis tairoto sp. nov

It is important to decipher the diversity and distribution of benthic dinoflagellates, as there are many morphologically indistinct taxa that differ from one another in production of potent toxins. To date, the genus Ostreopsis comprises twelve described species, of which seven are potentially toxic and produce compounds presenting a threat to human and environmental health. In this study, isolates previously identified as "Ostreopsis sp. 3" were sampled from the area where it was first reported, Rarotonga, Cook Islands, and have been taxonomically and phylogenetically characterised as Ostreopsis tairoto sp. nov. Phylogenetically, the species is closely related to "Ostreopsis sp. 8", O. mascarenensis, "O. sp. 4", O. fattorussoi, O. rhodesiae and O. cf. siamensis. Previously, it was considered a part of the O. cf. ovata complex but can be distinguished from O. cf. ovata based on the small pores identified on this study, and from O. fattorussoi and O. rhodesiae based on relative lengths of the 2' plates. No known palytoxin -like compounds were detected in strains investigated in this study. Strains of O. lenticularis, Coolia malayensis and C. tropicalis were also identified and described. This study advances our knowledge of biogeography, distribution, and toxins of Ostreopsis and Coolia species.