Achnanthes trachyderma Riaux-Gobin & Compère & Hinz & Ector 2015, comb. nov.
Creators: name: Riaux-Gobin, Catherine
name: Compère, Pierre
name: Hinz, Friedel
name: Ector, Luc
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Chromista
Ochrophyta
Bacillariophyceae
Achnanthales
Achnanthaceae
Achnanthes
Achnanthes trachyderma

description: Achnanthes trachyderma (F.Meister) comb. nov. (Figs 19, 20, 27–29, Table 2)   
 Basionym: Cocconeis trachyderma F.Meister, Berichte der Schweizerischen Botanischen Gesellschaft 44: 99, figs 63, 64. 1935 (figures reproduced here as Figs 19, 20).   
 Translation of the original diagnosis:—‘Valves elliptical with elongate, capitate endings, 29 to 32 μm long, 14 to 15 μm wide. Raphe valve with 26 radiate, punctuate-dotted striae and a stauroid central area, which extends beyond the midline of the half valve. Rapheless valve with a very narrow pseudoraphe and 9 to 11 coarsely punctate striae in 10 μm. Not rare in Nagasaki’.   
 Type: — JAPAN. Nagasaki, ‘shell of a marine snail from Nagasaki’, see Materials & Methods (lectotype here designated among the numerous slides from Nagasaki studied by Meister and containing this species: Z!, slide 3409008 in coll. F. Meister’s, illustrated here as Fig. 29. See Table 1).   
 Type observation:— The taxon is rare in F. Meister’s and M. Voigt’s slides. The individuals are small (ca. 25.6 μm long, 13.2 μm wide; ca. 11.5 SV striae in 10 μm and 25.5 RV striae in 10 μm), relatively narrow (L/W: 1.94), with wellmarked shoulders near the apices. The RV stauros is wide-ranging and thin, reaching almost the margins (Fig. 29). It can be remarked that the Nagasaki material also contains individuals slightly bigger (ca. 33.1 μm long, 17.4 μm large, 10.2 SV striae in 10 μm and 21.3 RV striae in 10 μm) but with an extended stauros as in the smaller individuals.   
 Remarks:—M. Voigt, in his hand notes about ‘ Cocconeis trachyderma v. elliptica Mfrd. Vgt. ’ (an undescribed variety marked from slide 22045, Nagasaki: ‘similar Meister’s type’) refers to ‘ Achnanthes ?’ as a remark, proving his doubts about its belonging to Cocconeis. Meister (1935: 99) also illustrated a SV of Cocconeis citronella from his Nagasaki material, with the remark that the latter has a lanceolate pseudoraphe, being narrow in Cocconeis trachyderma. Furthermore, Meister (1935: 99) specified that the central area is much shorter in Cocconeis citronella than in C. trachyderma.   
 Material from Society Archipelago (South Pacific): —(LM: n=3, Figs 30–32; SEM, n=21, Fig s 45–57). The individuals from the Society Archipelago are always small (25.6 + 2.9 μm long; 13.2 + 0.9 μm wide), the SV stria density is higher than in A. citronella (Table 1) and the stauros is extended; the SV sternum is narrow. This taxon is frequent in Tahiti and Moorea Islands. The morphology of the South Pacific taxon (Figs 30–32) roughly matches that of Achnanthes trachyderma comb. nov. The SEM examination allows to add some details to the diagnosis: the SV is strongly convex, one row of SV large areolae lies on each side of the narrow sternum (Figs 45–47), the SV apices are void of areolae except in rare cases (Fig. 46, arrowhead), the valvocopula system lacks fimbriae (Fig. 47, arrowhead). The SV areolae hymenes are externally smooth (with no apparent perforations or slits, Fig. 49), and lying under the valve face (Fig. 49, arrow); in internal view they show a complex structure with a grid pattern (Figs 48, 50, 51). The cingulum is composed of the valvocopulae and an additional copula (C in Fig. 49). The SV striae (11.5 + 0.7 striae in 10 μm) are parallel in mid-valve to only slightly radiate at the apices (Fig. 50). The RV is slightly concave (Fig. 52), finely striated (25.5 + 1 striae in 10 μm), with striae strongly radiate and composed of small areolae internally closed by domed hymenes (Fig. 55, arrowhead), with one row of longer areolae near the margin (Fig. 52, arrow). The raphe is filiform and straight, the axial area narrow, the central raphe endings straight and close to each other, the terminal raphe fissures very slightly undulating and continuing on the mantle (Figs 56, 57). The central area is enlarged in a narrow but extended stauros delineated on the margins by short striae (Fig. 53, arrow; Fig. 54, arrowheads). Helictoglossae are low (Fig. 53, arrowhead).
description: Published as part of Riaux-Gobin, Catherine, Compère, Pierre, Hinz, Friedel & Ector, Luc, 2015, Achnanthes citronella, A. trachyderma comb. nov. (Bacillariophyta) and allied taxa pertaining to the same morphological group, pp. 101-119 in Phytotaxa 227 (2) on page 108, DOI: 10.11646/phytotaxa.227.2.1, http://zenodo.org/record/13635194