Gomphoneis oreophila

Gomphoneis oreophila Stancheva & Kociolek, sp. nov. (Figs 46–71)

LM observations

Valves are nearly lanceolate, slightly clavate with rounded head pole and narrower foot pole (Figs 46–57). Margins are straight to convex and tumid at the center. Cells are 10.3–16 μm wide, 51–105 μm long; initial valves 15–17 μm wide, 120–125 μm long (Figs 53, 54). Axial area is relatively narrow, straight and slightly expanded only at the center to form a small linear-elliptical central area bearing one stigma (Figs 46–52). Raphe is slightly arched, distinctly lateral. Striae are nearly parallel to slightly radiate in the center, more strongly radiate toward the poles, 10–12 in 10 μm. Striae distinctly biseriate. Longitudinal lines located close to the valve margin (submarginal, Figs 49, 52, 54, 56) better visible when the valve is tilted. Initial valves bent, tumid in the center , bearing in the central area one stigma and 2 to many areolae (Figs 53, 54). Frustules are cuneate in girdle view with single irregular row of puncta missing in the central part (Fig. 58).

SEM observations Externally, the striae are composed of double rows of circular puncta which extend onto the mantle (Figs 59, 60, 62). The rape is more or less straight, or slightly arched, but not undulate (Figs 59, 60). Distal raphe ends are slightly bent before the apices and extend into the mantle (Figs 62, 63). Spines are not present at the head pole (Figs 61–63). At the foot pole the apical pore field is separated from the striae by unornamented silica, and the porelli are distinct and larger than the puncta (Figs 64). Externally, one round stigma is visible in the central area (Fig. 65), accompanied by several areolae in the initial cells (Fig. 66).

Internally, a large axial plate, narrow marginal lamina, and pseudosepta at both poles can be seen (Fig. 67). The axial plate terminates before reaching the helictoglossa at the foot pole (Figs 67, 70) where radiate striae with circular puncta are visible (Figs 70, 71). The marginal lamina is narrower near the central area (Figs 68, 69). The elongate central nodule is slightly raised and bears a slit-like stigma and recurved proximal raphe ends (Fig. 68).

Type:—USA. California: Rice Creek, Sierra Nevada Mts, 40.39999º N, 121.44109º W, Jennifer York, July 1, 2015 (holotype UC2050496 circled specimen on slide; isotype RS! 009, circled specimen on slide and material, CSUSM, USA).

Etymology:—This species epithet means “mountain-loving” referring to where it has been found.

Distribution and ecological notes:—Found only in the type locality which is high elevation site in the Sierra Nevada Mts, CA (1902 m a.s.l.). Habitat is characterized by low nutrients (TN 0.04 mg L-1, TP 0.05 mg L-1), low conductivity (74.8 μS cm-1), slightly alkaline (62 mg L-1 CaCO3), and pH 8.3 (see Table 1).

Comments: —The large size and position of the longitudinal lines near the margin suggest a close relationship between this taxon and species such as G. herculeana (Ehrenb.) Cleve (1894: 73), G. mammilla (Ehrenb.) Cleve (1894: 73) and G. minuta (Stone) Kociolek & Stoermer (1988: 56). However, in these species the longitudinal lines are positioned approximately midway between the axial area and margin, or closer to the axial area, and apical spines are common (Kociolek & Stoermer 1988). The lanceolate shape of this species clearly separates it from these large species of the genus, as well as Gomphoneis linearis Kociolek & Stoermer (1986: 146–7) in which the longitudinal lines are positioned close to the valve margin. The latter species, known from only a few specimens from a single locality in Oregon (Kociolek & Stoermer 1986), differs in the shape of the valves, being more linear in outline (as opposed to having a distinctly lanceolate outline), has proportionately more broadly rounded headpoles, and is smaller (Table 2). Furthermore, the central striae around the stigma are radial with closely spaces tips in some specimens (see Kociolek & Stoermer 1986, Figs 25 and 26), in contrast to nearly parallel central striae in G. oreophila.

• Author
  Stancheva and Kociolek 0
• Length Range
  51–105 µm
• Width
  10.3–16 µm
• Striae in 10µm
  10–12