Exanthemachrysis Lepailleur 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 : 31

Exanthemachrysis Lepailleur emend. Véron

Figs 1–5

Included species

Exanthemachrysis gayraliae Lepailleur 1970 : figs 1–4. – Bendif et al. 2011: fig. 4.

Exanthemachrysis fresneliae Véron sp. nov.

Emended description

Dominant stage of non-motile cells slightly ovate, embedded in mucilage. Brownish-green parietal chloroplast with a bulging pyrenoid forming an anterolateral protuberance on the cell body. Motile cells flattened oval, metabolic with three appendages. Distal attenuation of the bipartite posterior flagellum, haptonema short but not vestigial. Stalked ovoid knob-scales may be present. Anterolateral bulging pyrenoid, partially covering and bordering a pit where the flagella emerge, delimited from the chloroplast stroma by osmiophilic globules forming a stigma near the insertion of the appendages.

Figures

Fig. 1. Exanthemachrysis fresneliae Véron sp. nov. (AC35), palmelloid and swimming cells, LM images. A. Benthic colonies of non-motile sister cells embedded in non-stratified M (black arrows) with storage granules of P (white arrows). B. Benthic non-motile cell embedded in non-stratified M (black arrow) with storage granule of P (white arrow), bilobed C and anterior bulging PY. C. Apical view (bottom right) and side view (up left) of 2 swimming cells with conspicuous S-shaped AF (black arrows) emerging almost mid-ventrally from a pit (white arrows). D. Side view of motile cells with bulging PY (black arrows). Scale bars: A = 5 µm; B = 1 µm; C–D = 2 µm.

Fig. 2. Exanthemachrysis fresneliae Véron sp. nov. (AC35), palmelloid sister cells, TEM image (Fix 1). Benthic colony of non-motile sister cells embedded in a common non-stratified M envelope (white stars); parietal C with helicoidal arrangement of the TH lamellae and a bulging PY near the F bases perpendicular to each other (white arrows), with the basal bodies connecting to the microtubular root (black arrows) running to the central area of the cell. Secretory vesicles from G (black star) ready to discharge content near the pit where the F emerge. Scale bar: 0.5 µm.

Fig. 3. Exanthemachrysis fresneliae Véron sp. nov. (AC35), palmelloid cell, TEM image (Fix 1). Nonmotile benthic cell embedded in non-stratified M showing single parietal C with a bulging PY at its end. Row of few osmiophilic vesicles forming an E in C stroma located at the junction of TH and PY. Both F bases (white arrows) positioned in continuity with a notch in the nucleus facing the sub-ventral pit (black arrow). Scale bar:1 µm.

Fig. 4. Exanthemachrysis fresneliae Véron sp. nov. (AC35), flagellar apparatus of motile cells. A. SEM image of side view of swimming cell with a 3–4 µm long conspicuous sinusoidal S-shaped and slightly tapering AF emerging almost mid-ventrally and thickly covered by KS (white arrows). B–C. Negative staining image. B. Detail of the 3 appendices, the AF, the H and the PF composed of 2 parts of sub-equal lengths with a distal attenuation. C. Detail of the AF of a cell bearing ovoid KS (black arrows) down to the base, in regular helicoidal rows. Scale bars: A–B = 1 µm; C = 0.1 µm.

Fig. 5. Exanthemachrysis fresneliae Véron sp. nov. (AC35), flagella, plasma membrane and knob-scales, TEM images (Fix 1). A. Longitudinal section of the pit area with 2 emerging F (white arrows = central microtubules) surrounded by a sheath of reticulum enclosing their bases. Plasma membrane (black arrow), underlined with endoplasmic reticulum (white stars), covered with KS. B. Details of the cell surface in the region of F emergence. Oblique sections of F bases with central microtubules (white arrow). Stalked ovoid KS partially covering the F bases and the plasma membrane. C. G with cisternae and secretory vesicles containing KS (white arrows). Scale bars: A–B = 50 nm; C = 0.5 µm.