Reclassification of Gonyaulax verior (Gonyaulacales, Dinophyceae) as Sourniaea diacantha gen. et comb. nov.

ABSTRACT

Gonyaulax verior

was initially described as Amylax diacantha from Belgian coastal waters a century ago but its detailed morphology needed restudy. Here, we established nine strains of G. verior by germinating cysts or isolating cells from localities from the European Atlantic to the Caspian Sea and the Pacific Ocean. Both cyst and thecal morphology were examined by light and scanning electron microscopy. SSU, LSU and/or ITS-5.8S rRNA gene sequences were obtained from all strains. Cells of G. verior have a plate formula of Po, 4′, 2a, 6-7′′, 6C, 6S, 6′′′, 1p, 1′′′′ with an L-type ventral organisation, characterised by two either straight or curved antapical horns of variable length. Cysts of G. verior are oval, smooth and contain one or two yellow accumulation bodies. The maximum-likelihood and Bayesian inference analyses based on SSU and LSU rRNA gene sequences revealed two clades of G. verior, referred to as ribotypes A and B. Genetic distances based on ITS-5.8S rRNA gene sequences within the same ribotype were less than 0.06, but greater than 0.32 between ribotypes. G. verior is reclassified as Sourniaea diacantha gen. et comb. nov., which is attributed to Lingulodiniaceae together with Pyxidinopsis, Lingulodinium and Amylax. Our results suggest that Lingulodiniaceae can be separated from Protoceratiaceae and Gonyaulacaceae based on ventral organisation, apical complex, ventral pore and number of anterior intercalary plates. One strain of S. diacantha was examined for yessotoxin production by LC-MS/MS but did not produce toxin.

KEYWORDS:

• Amylax diacantha
• Cysts
• Dinoflagellate
• Gonyaulax longispina
• Molecular phylogeny

ACKNOWLEDGEMENTS

Urban Tillmann is acknowledged for interesting taxonomic discussions. Two anonymous reviewers and the editor are thanked for constructive suggestions that improved the manuscript greatly.

SUPPLEMENTARY MATERIAL

The supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China (2016YFE0202100), the National Natural Science Foundation of China (41676117), the KRIBB Research Initiative Program, the Marine Biotechnology Program funded by the Ministry of Oceans and Fisheries of the Korean Government (20170431), and by the KIOST (PE99721) project. Funding for collection of sediments in coastal waters of British Columbia (Canada) was provided by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to VP.