Rebecca Green emend. Véron

Véron, Benoît, Rougier, Etienne, Taylor, Anthony & Goux, Didier, 2023, New species of Pavlovophyceae (Haptophyta) and revision of the genera Exanthemachrysis, Rebecca and Pavlova, European Journal of Taxonomy 861, pp. 21-47 : 35

Rebecca Green emend. Véron

Figs 7–9

Included species

Rebecca salina (Carter) Green 2000 . – Nephrochloris salina Carter 1937 : pl. 2, figs 10–22. – Pavlova mesolychnon van der Veer 1969 : figs 1–21. – Pavlova salina (Carter) Green 1976 : pls. 1–2.

Rebecca helicata (van der Veer) Green 2000 . – Pavlova helicata van der Veer 1972 : figs 1–8.

Rebecca billardiae sp. nov.

Emended description

Cells solitary, free-swimming, sometimes immobile, elongated and slightly compressed or angular to almost cubic, with two unequal flagella and short haptonema. Longer anterior flagellum with fine nontubular hairs, posterior flagellum vestigial. A pit or canal penetrating the cell near the long anterior flagellum. Clavate or mono-constricted scales on the cell body and rows of di- or trimeric scales on the anterior flagellum. Pale yellow-green to golden-brown bilobed single chloroplast with parallel and helicoidal thylakoid arrangement, stigma and pyrenoid absent.

Figures

Fig. 7. Rebecca billardiae Véron sp. nov. (AC537), flagellate motile and non-motile cells, LM images. A. Gathering angular non-swimming flagellate cells with an S-shaped AF (white arrows). B. Polyhedral free-swimming cell with bilobed lateral golden-brown C, S-shaped AF (white arrow) and posterior beaded filipodium (black arrows). C–D. Cells of various shapes showing sub-apical insertion into a pit (white arrows) of the S-shaped AF. Posterior branched beaded filipodia present at the terminal part of the cell (black arrows). E. Ventral view of an angular free-swimming cell with sub-apical insertion of S-shaped AF into a pit (white arrow). F. Rounded cells with S-shaped sub-apically inserted AF (white arrow), posterior filipodium (black arrow) and bilobed golden-brown C. Scale bars: Scale bars: A = 4 μm; B–D, F = 5 μm; E = 1 μm.

Fig. 8. Rebecca billardiae Véron sp. nov. (AC537), flagella, plasma membrane and knob-scales, TEM images (A–D, G–H = Fix 1; E–F = Fix 2). A. Angular cell with bilobed C and TH lamellae grouped by 3 sometimes twisted. B. Longitudinal section of a motile cell displaying the AF bearing few KS (white arrows) and the adjacent H. C. Cross-section of the sub-apical pit of a non-swimming cell containing the bases of H and F (transverse section – right, oblique section – left) sheathed by cytoplasm and surrounded by the plasma membrane (black arrow). D. Inflated G secretory vesicles unloading their materials including KS near the flagellar insertion zone. E. Periphery of a cell showing continuity of the plasma membrane along the curved AF, both covered with pedunculate KS (white arrows). F. Isolated plasma membrane retaining pedunculate mono-constricted club-shaped KS sporadically dispersed on its surface. G. Longitudinal section of a motile cell displaying the AF and PF both bearing few KS (white arrows) and the naked H. Note discharge of KS by G cisternae. H. Reduced PF cut in median longitudinal section showing microtubules and bearing a dense pedunculate club-shaped KS (white arrow). Central pair of microtubules is absent. Scale bars: A = 2 µm; B–D, H = 0.5 µm; E–F = 50 nm; G = 1 µm.

Fig. 9. Rebecca billardiae Véron sp. nov. (AC537), flagellar apparatus details of motile cells. A–E. SEM images. A. Ventral view of a cuboid cell with the S-shaped distally tapered AF and curved H. B-C. Ventral views of angular cells with the S-shaped AF covered with KS, the vestigial PF and the curved bipartite H between both F. D-E. Details of the insertion the 3 appendages. D. Vestigial PF. E. Bipartite H with the proximal hook-shaped half and the distal half forming a pearl string structure. Note distally tapered AF. F–G. Negative staining images. F. Proximal part of the tomentose AF with multilayered KS (white arrow), extending after a bare proximal zone (black arrow) in the immediate vicinity of the cell. G. Details of mono-constricted (white arrows) KS covering the distally attenuated AF. Scale bars: A, C, E–F = 1 µm; B = 2 µm; D = 100 nm; G = 200 nm.