Taxonomy and toxicity of a bloom-forming Ostreopsis species (Dinophyceae, Gonyaulacales) in Tahiti island (South Pacific Ocean): one step further towards resolving the identity of O. siamensis.

Type Article
Date 2020-09
Language English
Author(s) Chomérat NicolasORCID1, Bilien GwenaelORCID1, Viallon Jérôme2, Hervé FabienneORCID3, Réveillon DamienORCID3, Henry Kévin2, Zubia Mayalen4, Vieira Christophe5, Ung André2, Gatti Clémence Mahana Iti2, Roué Mélanie2, Derrien AmelieORCID1, 6, Amzil ZouherORCID3, Darius Hélène Taiana2, Chinain Mireille2
Affiliation(s) 1 : Ifremer, LER BO, Station of Marine Biology of Concarneau, Place de la Croix, F-29900 Concarneau, France
2 : Institut Louis Malardé, Laboratoire des Micro-algues toxiques, UMR 241-EIO, PO box 30, 98713 Papeete, Tahiti, French Polynesia
3 : Ifremer, Phycotoxins Laboratory, BP 21105, F-44311 Nantes Cedex 3, France
4 : Université de Polynésie Française, UMR 241-EIO, PO Box 6570, 98702 Faa'a, Tahiti, French Polynesia
5 : Kobe University Research Center for Inland Seas, Rokkodai, Kobe 657-8501, Japan
6 : Institut de Recherche pour le Développement (IRD), UMR 241-EIO, PO box 529, 98713 Papeete, Tahiti, French Polynesia
Source Harmful Algae (1568-9883) (Elsevier BV), 2020-09 , Vol. 98 , P. 101888 (20p.)
DOI 10.1016/j.hal.2020.101888
WOS© Times Cited 10
Keyword(s) Dinoflagellate, ITS-5.8S rDNA, LSU rDNA, Microscopy, Morphology, Ostreocin, Phylogeny

Among dinoflagellates responsible for benthic harmful algal blooms, the genus Ostreopsis primarily described from tropical areas has been increasingly reported from subtropical and temperate areas worldwide. Several species of this toxigenic genus produce analogs of palytoxin, thus representing a major threat to human and environmental health. The taxonomy of several species needs to be clarified as it was based mostly on morphological descriptions leading in some cases to ambiguous interpretations and misidentifications. The present study aims at reporting a benthic bloom that occurred in April 2019 in Tahiti island, French Polynesia. A complete taxonomic investigation of the blooming Ostreopsis species was realized using light, epifluorescence and field emission electron microscopy and phylogenetic analyses inferred from LSU rDNA and ITS–5.8S rDNA regions. Toxicity of a natural sample and strains isolated from the bloom was assessed using both neuroblastoma cell-based assay and LC-MS/MS analyses. Morphological observations showed that cells were round to oval, large, 58.0–82.5 µm deep (dorso-ventral length) and 45.7–61.2 µm wide. The cingulum was conspicuously undulated, forming a ‘V’ in ventral view. Thecal plates possessed large pores in depressions, with a collar rim. Detailed observation also revealed the presence of small thecal pores invisible in LM. Phylogenetic analyses were congruent and all sequences clustered within the genotype Ostreopsis sp. 6, in a subclade closely related to sequences from the Gulf of Thailand and Malaysia. No toxicity was found on the field sample but all the strains isolated from the bloom were found to be cytotoxic and produced ostreocin D, a lower amount of ostreocins A and B and putatively other compounds. Phylogenetic data demonstrate the presence of this species in the Gulf of Thailand, at the type locality of O. siamensis, and morphological data are congruent with the original description and support this identification.

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Chomérat Nicolas, Bilien Gwenael, Viallon Jérôme, Hervé Fabienne, Réveillon Damien, Henry Kévin, Zubia Mayalen, Vieira Christophe, Ung André, Gatti Clémence Mahana Iti, Roué Mélanie, Derrien Amelie, Amzil Zouher, Darius Hélène Taiana, Chinain Mireille (2020). Taxonomy and toxicity of a bloom-forming Ostreopsis species (Dinophyceae, Gonyaulacales) in Tahiti island (South Pacific Ocean): one step further towards resolving the identity of O. siamensis. Harmful Algae, 98, 101888 (20p.). Publisher's official version : , Open Access version :