Gonyaulacalean tabulation revisited using plate homology and plate overlap, with emphasis on the ventral area (Dinophyceae)

ABSTRACT

We propose a standardization of the gonyaulacalean (Dinophyceae) Kofoidian plate tabulation using plate homology and overlap patterns, on the basis of a new morphological study of species belonging to 17 genera previously classified in the order Gonyaulacales: Acanthogonyaulax, Alexandrium, Amphidoma, Azadinium, Ceratium, Ceratocorys, Cladopyxis, Cribroperidinium, Fragilidium, Gonyaulax, Heterodinium, Lingulodinium, Paleophalacroma, Peridiniella, Spiraulax, Triadinium and Tripos. The plate immediately left of the flagellar pore is reinterpreted as a sulcal plate rather than its more conventional interpretation as a postcingular plate. With this new perspective the studied genera fall into two groups: 1) genera with only five Kofoidian postcingular plates (Acanthogonyaulax, Alexandrium, Ceratocorys, Cribroperidinium, Gonyaulax, Lingulodinium, Spiraulax and Triadinium) or six postcingular plates (Fragilidium); 2) genera with six Kofoidian postcingular plates, as well as differences in episomal plate patterns (Amphidoma, Azadinium, Cladopyxis, Heterodinium, Paleophalacroma and Peridiniella). The former are here considered true gonyaulacaleans, whilst the latter need further study for a more appropriate phylogenetic placement, and are here informally called non-gonyaulacaleans. In these non-gonyaulacalean genera, the first posterior intercalary plate overlaps the first postcingular plate/anterior left sulcal plate, but is always overlapped by the second postcingular homologue plate (a plate in similar position) demonstrating that the first plate of the postcingular series is not homologous in the two groups. Additionally, the identical overlapping pattern shows that the anterior left sulcal plate (Ssa) in gonyaulacaleans with five postcingular plates is the same plate as the first postcingular plate in gonyaulacaleans with six postcingular plates. Kofoidian definitions of posterior intercalary plates as well as antapical plates remain the same and are applied here. The Kofoidian hyposomal plate formula for gonyaulacaleans would then be 5–6''', 2p, 1''''.

KEYWORDS:

• Cladopyxidaceae
• Dinoflagellate plate homologues
• Dinoflagellates
• Kofoidian labelling system
• Postcingular plates

ACKNOWLEDGEMENTS

The Regional Council of Brittany, the General Council of Finistère and the urban community of Concarneau-Cornouaille-Agglomération are acknowledged for funding the Sigma 300 FE-SEM of the Station Marine de Concarneau. We like to gratefully thank Lucy Edwards for providing residue to study Cribroperidinium, and Andrés Boltovskoy and Lander Blommaert for sending freshwater plankton samples. Elisabeth Nézan and Nicolas Chomérat are acknowledged for making SEMs of Fragilidium available for viewing. Oregon State University Research Incentive Program contributed funds for SEM imaging of Indian Ocean species. Rob Fensome and an anonymous reviewer are thanked for constructive comments that significantly improved the manuscript. The samples from the Coral Sea were kindly supplied by Prof. Gustaaf Hallegraeff, many years ago, for MCCM's early studies on podolampadaceans. MCC-M also thanks Brian Verwey for taking the samples during the NAAMES 3 campaign. Prof. Marta Torres (Oregon State University) is thanked for sampling in the Mediterranean Sea for MCC-M. NAAMES was supported by a NASA Grant [grant number NNX15AF30G] to Dr. Michael J. Behrenfeld (Oregon State University).

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

SUPPLEMENTARY MATERIAL

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