Gomphoneis subtiloides Q. You & Kociolek, 2013

You, Qingmin, Kociolek, John Patrick & Wang, Quanxi, 2013, New Gomphoneis Cleve (Bacillariophyceae: Gomphonemataceae) species from Xinjiang Province, China, Phytotaxa 103 (1), pp. 1-24 : 3-5

Gomphoneis subtiloides Q. You & Kociolek , sp. nov. ( Figs 1 –14; figure 3 is holotype)

Type:— CHINA. Little Kalakule Lake , Kunlun Mountains ( SHTU, slide XJ-071014! holotype illustrated in figure 3) .

In LM, valves lanceolate-clavate with headpole incised to weakly capitate and rounded, and broadly rounded footpole. Length 35.0–63.0 µm, breadth 6.4–9.4 µm. Axial area narrow, straight, expanded at the center to form a broad, rectangular central area bordering at the margins by 2–4 approximately equally-shortened striae. Stigmoids in the central area lacking. Raphe lateral, weakly undulate, with external proximal ends dilated, rounded, extending into central area; external distal raphe ends extending straight to valve terminus at both poles. Internal proximal raphe ends small, deflected in the same direction, while internal distal raphe ends (“terminal nodules”) are distinct, positioned well before valve terminus. Costate striae number 11–13 in 10 µm, arched about center of valve, strongly radiate, becoming parallel towards poles. Septa and pseudosepta prominent. Apical pore fields relatively large, distinct.

In the SEM, the valve exterior (Figs 7–11) has doubly-punctate or biseriate striae that terminate as single rows around the center area (Fig. 10). The proximal raphe ends are dilated and appear rounded (Fig. 10). At the headpole, the striae are composed of two alternating rows of striae (Fig. 9); some puncta are slit like and form a single slit-like punctum (Fig. 9). The distal raphe ends extend on to the mantle (Fig. 9). The footpole (Fig. 11) has a large apical pore field with the porelli the same size and structure as the puncta. The porelli are organized into rows, which are much closer together than the striae; they are located next to the striae, and are therefore undifferentiated structurally and spatially from them. There is a slight bend in the distal raphe end, before it bisects the apical pore field and extends onto the valve mantle (Fig. 11). In rare cases, the striae will branch (Fig. 8).

Internally, the raphe is positioned on a raised rib and the proximal ends are recurved along the outer edges of the raised central nodule (Fig. 13). The central area is expanded and unornamented, except near the margin (Fig. 13). The striae are wide and formed by two rows of puncta. The striae around the central area taper towards the center and terminate in one row of puncta (Fig. 13). At both the headpole (Fig. 12) and footpole (Fig. 14) the helictoglossae are prominent, positioned in line with the raphe; there is a distinct pseudoseptum (Fig. 14).

Etymology:— The species name is based on the outline of the valve being similar to Gomphonema subtile Ehrenb. (1843: 416).

Distribution and ecology:— Little Kalakule Lake, Kunlun Mountains, Xinjiang, China, altitude 3300m, pH 9.0, collected in the wetland near the lake (summarized in Table 1).

Observations:— Gomphoneis subtiloides differs from G. pseudosubtiloides in having a less capitate headpole.

Figures

PLATE 1, FIGURES 1–6. Gomphoneis subtiloides, LM. Valve views showing size diminution series. Figure 3 is the holotype. Scale bars = 10 µm for all figures.