Electron microscopy of a 1991 spring plankton sample from the Argentinean Shelf reveals the presence of four new species of the Amphidomataceae (Dinophyceae)

Abstract

The dinophycean family Amphidomataceae encompasses the genera Azadinium and Amphidoma, which attract considerable attention because of their production potential for azaspiracids, i.e. lipophilic polyether phycotoxins. Many new species of Amphidomataceae were described in the last decade, but the diversity probably is not fully explored yet. In a continuation of a previous study, Amphidomatacean diversity of the 1991 spring plankton bloom along the Argentinean shelf was investigated. Based on morphology as inferred from scanning electron microscopy, three new species of Amphidoma and one new Azadinium are described. Azadinium asperum sp. nov. differed in size and shape from other Azadinium and had a characteristically rough and slightly granular surface of thecal plates. Amphidoma trioculata sp. nov. and Amphidoma cyclops sp. nov. differed by shape from most other Amphidoma, and can be differentiated from one another by the presence/absence of a antapical pore and by the size of a ventral depression. Amphidoma alata sp. nov. was unique by a conspicuous wing-like sulcal list. Calculations based on the total number of small dinoflagellates and on relative scanning electron microscopy quantification indicated that density of all four species was fairly high (7-40 × 10 3 cells L −1 ), so a large number of cells could be investigated in the sample. A few more single cells in the sample are attributable to Amphidomataceae but do not belong to one of the described species. This indicates that the diversity of the group is still not fully explored.

Plankton Multiproxy Analyses in the Northern Patagonian Shelf, Argentina: Community Structure, Phycotoxins, and Characterization of Toxic Alexandrium Strains

“…Blooms composed of various species of Azadinium spp. and Amphidoma spp., two genera known for the production of azaspiracids (AZAs) (Tillmann, 2018a), have been described from the Argentine shelf (Akselman and Negri, 2012;Tillmann et al, 2018;Tillmann and Akselman, 2016;Tillmann, 2018b), but the production potential of AZAs by the local species/populations is yet known only for Azadinium poporum . The analyses of phytoplankton composition and toxin production may lead to the understanding of carbon fluxes through the pelagic food web and to the benthos, where large beds of the scallop Zygochlamys patagonica are located (Bogazzi et al, 2005;Franco et al, 2017).…”

Morphological and molecular characterization of multiple new Azadinium strains revealed a high diversity of non‐toxigenic species of Amphidomataceae (Dinophyceae) including two new Azadinium species in Irish waters, North East Atlantic

“…2020), the Norwegian coast (Tillmann et al . 2018a) or the Argentinean shelf (Tillmann & Akselman 2016; Tillmann 2018; Tillmann et al . 2019), and thus seem to be the rule and not an exception.…”

Field observations on rare or unnoticed dinoflagellates from the Argentine Sea

“…Akselman 1985Akselman , 1986Akselman , 1987Akselman & Negri, 2012;Akselman et al, 2015;Fabro et al, 2015;Antacli et al, 2018;Tillmann et al, 2019;Sunesen et al, 2020a). However, the recent description of new dinoflagellate species (Tillmann & Akselman, 2016;Boutrup et al, 2017;Tillmann, 2018;Tillmann et al 2018;Sunesen et al, 2020b) and the finding of new records (e.g. Fabro et al, 2016Fabro et al, , 2017Fabro et al, , 2019Tillmann et al, 2016) suggest that dinoflagellate diversity in the Argentine Sea is higher than previously known.…”