Studies on the benthic genus Sinophysis (Dinophysales, Dinophyceae): I. a taxonomic investigation from Martinique Island, including two new species and elucidation of the epithecal plate pattern

Abstract:

The benthic dinoflagellate genus Sinophysis is known from tropical and temperate areas with seven species described. To date, none of them has been fully characterized, and the epithecal plate pattern remains unclear at the genus level. A taxonomic investigation from Martinique Island facilitated the characterization of six species: Sinophysis microcephala, Sinophysis ebriola, Sinophysis stenosoma, Sinophysis cf. verruculosa and two new species. They were studied and illustrated by light and scanning electron microscopy. The two new species, Sinophysis hoppenrathiana sp. nov. and Sinophysis vespertilio sp. nov., were characterized morphologically and shown to differ from all existing species. The cells of S. hoppenrathiana sp. nov. were medium-sized, 32–40 μm long and 23–30 μm deep. They had a peculiar ovate shape, a small crown-like epitheca and the hypotheca was ornamented by shallow alveolae. Cells of S. vespertilio sp. nov. were small, 26–31 μm long and 20–25 μm deep. They were oval in shape with a medium epitheca, and thecal plates were devoid of ornamentation. The epithecal plate pattern was elucidated using scanning electron microscopy. In all species, the epitheca was asymmetrical, pointing to the right ventral side and composed of four epithecal plates E and two apical plates A. The E₁ plate was the most ventral but partially hidden by projections of other plates. The large plate E₂ bordered the cingulum on the left side, while the large plates E₃ and smaller plate E₄ were on the right side. Two other plates, A₁ and A₂, were located more apically, or on the left epithecal side, and encircled a large apical pore. These plates formed prominent projections in all species. In some species, an additional accessory pore was observed more ventrally and located on the suture between E₁ and E₂. The relative sizes of epithecal plates were variable among the species. These results confirmed that the pattern is consistent with Dinophysales but with a very different arrangement. The generic diagnosis of Sinophysis is emended to encompass these findings.

Key Words::

• Dinoflagellate
• Diversity
• Epitheca
• Microscopy
• Morphology
• Plate pattern
• Taxonomy
• SEM
• Sinophysis hoppenrathiana sp. nov.
• Sinophysis microcephala
• Sinophysis vespertilio sp. nov.

ACKNOWLEDGEMENTS

The author wishes to thank Maurice Loir for sampling of benthic dinoflagellates in the Caribbean and long term collaboration, and Elisabeth Nézan for her support with SEM observations and valuable comments to improve the manuscript. I am grateful to Nicolas Gayet for his help in processing the samples for SEM and to Gwenael Bilien for the suggestion of a species name. I would like to acknowledge two anonymous reviewers, the associate editor and editor-in-chief for their useful comments on the manuscript.

SUPPLEMENTARY DATA

Supplementary data associated with this article can be found online at http://dx.doi.org/10.2216/16-24.1.s1.