Re-investigation of Gymnodinium natalense (Dinophyceae), a tidal pool dinoflagellate from South Africa and the proposal of a new combination Ansanella natalensis : Ansanella natalensis comb. nov.

A small tidal pool bloom-forming dinoflagellate, Gymnodinium natalense T. Horiguchi & Pienaar, sampled from its type locality in South Africa, was re-investigated and a new combination Ansanella natalensis (T. Horiguchi & Pienaar) Dawut, Sym T. Horiguchi comb. nov. was proposed. The species was originally described as a new species of the genus Gymnodinium, and later, Moestrup et al. (2009a) transferred it to their new genus Biecheleria based on morphological resemblance. However, no molecular data were available at that time, making confirmation of its phylogenetic affinities impossible. An organism more-recently isolated from the type locality was confirmed as G. natalense based on its morphological features. In addition, we were able to characterize details of its surface structure, which were lacking in the original description. Cells were covered with small, mostly hexagonal, amphiesmal vesicles (AV) arranged in 11-13 latitudinal rows. The episome contained an elongated amphiesmal vesicle (EAV) enclosing approximately 25 knobs in linear array. A phylogenetic analysis based on SSU rDNA sequences revealed that this dinoflagellate was closely related to Ansanella granifera the only member of the genus. The G. natalense shared numerous characteristics with A. granifera, such as the arrangement of AVs in a similar number of latitudinal rows, the shape and position of the EAV, the possession of a type E eyespot, a similar type of pyrenoid, the absence of a peduncle and nuclear chambers, the lack of a nuclear fibrous connective and no resting cyst-like cells. Yet, it also showed some morphological differences, i.e. the possession of a single chloroplast that lacks grana-like thylakoids, which separate it from A. granifera. These morphological features, along with its highly supported molecular affinity with A. granifera, led to the conclusion that this dinoflagellate represents a new member of this genus, i.e. A. natalensis comb. nov. The phylogenetic analysis showed no support for a close relationship with members of the genus Biecheleria.