Anorthoneis arthus-bertrandii De Stefano & Pennesi, 2018

Pennesi, Chiara, Majewska, Roksana, Sterrenburg, Frithjof A. S., Totti, Cecilia & Stefano, Mario De, 2018, Taxonomic revision and morphological cladistics analysis of the diatom genus Anorthoneis (Cocconeidaceae), with description of Anorthoneis arthus-bertrandii sp. nov., Phytotaxa 336 (3), pp. 201-238 : 232

Anorthoneis arthus-bertrandii De Stefano & Pennesi , sp. nov. ( Figs 130–143 )

Diagnosis:— valvae late ellipticae, 16–22 μm longae, 13–18 μm latae. Areovalva concava in area axiali et leviter convexa in area marginali. Sternum excentrico, lineare cum nodulo centrali conspicuo et eccentrico. Areovalva habet in valvae lato structuram striis cum monoseriatis (14–18 in 10 μm) quae constant ex areolis oblongis (10–14 in 10 μm). Implicatae rotae partes exteriores areolarum occludunt. Areovalva habet in limbo structuram striis biseriatis quae constant ex poroidis qui occlusi sunt hymenibus rimis cum inaequalibus. Raphovalva habet raphem rectam cum nodulo centrali et nodulis terminalibus oblongis. Striae monoseriatae (18–20 in 10 μm) quae constant ex poroidis qui occlusi sunt hymenibus rimis cum inaequalibus. Utraque valvocopula secta et caret fimbriis.

Holotype:— slide MDS 9 deposited at the Herbarium of the Stazione Zoologica “Anton Dohrn” of Naples, Italy. Figures 142 , 143 illustrates the holotype specimens.

Type locality:— INDONESIA. Epiphytic on seagrasses leaves collected in October 2005 along the coasts of Siladen Island, Sulawesi, Indonesia, (1° 38′ 25.23″ N, 124° 48′ 06.61″ E). Collected by Dr. Francesca Azzini, October 2005.

Etymology:— the specific epithet refers to Yann Arthus-Bertrand in recognition of his outstanding service in the promotion of scientific knowledge and its dissemination.

Description:— Valves broadly elliptical to ovoid in outline ( Figs 130, 133 , 136, 139, 142 and 143 ). Apical axis: 16–22 μm, transapical axis: 13–18 μm.

SV:— Externally, valve face slightly concave with a convex mantle, ending in a small marginal area covered by a row of very small pores ( Fig. 130 ). The eccentric sternum narrow, linear, developed entirely within the valve face, terminating close to the valve face-mantle junction ( Fig. 130 ). Central area small, circular, with very small, irregular, imperforated pores ( Figs 130, 131 ). Transapical striae strongly radiate, 14–18 in 10 μm, uniseriate, becoming biseriate in the last row of the mantle striae ( Fig. 132 ). Areolae circular to squared, 10–14 in 10 μm, internally occluded by rota-like vela ( Figs 131–135 ). Internally, the valve surface structures appear similar to the external ones, except for the larger central area ( Fig. 133 ).

RSV:— Externally, valve concave to convex close to the margin. The margin is covered by two irregular rows of very small pores ( Fig. 136 ). Raphe-sternum asymmetric, narrow and linear developed entirely within the valve face ( Fig. 136 ). Proximal raphe endings slightly expanded, coaxial, converging within a small, roundish and clearly asymmetrical central area ( Figs 136, 137 ). Distal raphe endings similar in shape, terminate in roundish submarginal areas ( Figs 136, 138 ). Transapical striae strongly radiate, 18–20 in 10 μm, uniseriate in the valve face becoming biseriate in the mantle ( Fig. 136 ). Areolae small, rounded, 22–24 in 10 μm, internally occluded by perforated vela ( Figs 139, 140, 141 ). On the mantle margin, at the end of each biseriate striae, one smaller areola is present ( Figs 136, 138 ). Internally, both the raphe-sternum and the small central nodule only slightly thickened ( Figs 139, 140 ). Proximal raphe endings simple, deflected in opposite directions ( Figs 139, 140 ); distal ones terminate in vestigial helictoglossae ( Figs 139, 141 ). Valvocopula open, with a smooth inner margin.

Figures

FIGURE 143. Relationship tree of the genus Anorthoneis generated using maximum parsimony method (Cladistic analysis). The black circles indicate probable homology changes, and the white circles represent probable homoplasy or ancestrally-derived homology changes. Circle number, top = character number (Table 3); circle number, bottom = character state (Table 3).

FIGURES 130–135. Anorthoneis arthus-bertrandii De Stefano & C. Pennesi, sp. nov., SEM images. (130) External view of sternum valve; (131) Detail of sternum valve showing the presence of vestigial perforations in hyaline-like central area; (132). Detail of the sternum valve mantle showing biseriate striae close to the valve margin; (133) Internal view of sternum valve; (134) Detail of the sternum valve (internally) showing the eccentric central area with vestigial perforations; (135) Detail of circular areolae internally occluded by rota-like vela. Figs 130, 133 = 5 μm; Fig. 134 = 2 μm; Figs 131, 132, 135 = 1 μm.

FIGURES 136–142. Anorthoneis arthus-bertrandii De Stefano & Pennesi, sp. nov., SEM images. (136) External raphe-sternum valve with asymmetric raphe branches; (137) Detail of coaxial central raphe endings (externally); (138) Detail of external distal raphe ending terminating in a roundish submarginal hyaline area (externally); (139) Internal view of raphe-sternum valve showing the thickening of sternum and small central nodule; (140) Detail of the internal, uncinated proximal raphe endings converging to the central nodule; (141) Detail of distal raphe ending terminating in a vestigial helictoglossa (internally). (142) Anorthoneis arthus-bertrandii De Stefano & Pennesi, sp. nov. from slide MDS 9 (Holotype), LM images. Scale bars: Fig. 140 = 10 μm; Figs 139, 142 = 5 μm; Fig. 137 = 2 μm; Figs 136, 138, 141 = 1 μm.