Staurophora brantii

Identification

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Description

Cells are solitary and enclosed within a laminated mucilage capsule. Cells contain one lobed plastid with a large lenticular pyrenoid. Valves are rhombic-lanceolate with broadly rounded and somewhat protracted apices. The valve face is curved in the transapical section, merging gradually into the deep mantle, which is shallower near the apices. The raphe sternum is narrow, somewhat thickened and slightly elevated at the central nodule. Overlapping girdle elements bear longitudinal rows of small, round poroids. Raphe branches are straight and filiform. External proximal raphe ends are bordered by lips and lie in spathulate grooves. Terminal raphe fissures are strongly curved and open toward the secondary side of the valve. Internal proximal raphe ends are bent in the same direction. Terminal fissures end internally in “moustache-shaped” helictoglossa. The axial area is narrow, linear and widens slightly near the central area. The central area is a broad transverse fascia, wider toward the margins and with a few shortened striae on one or both sides. Only the ends of the longest of these short striae are visible in valve view, making them appear to be more widely spaced than other striae. Striae are radiate and uniseriate and composed of small, round areolae.

Autecology

Staurophora brantii lives on fine sediments in streams of the Northwestern Great Plains. Most streams in this ecoregion are ephemeral or intermittent, typically consisting of a series of interconnected pools with bottoms composed of fine silt and decomposing organic matter. Records of this taxon in the Montana Diatom Database are distributed by state as follows: Montana (118), North Dakota (3), South Dakota (10), and Wyoming (20). Abundance-weighted mean values for water quality variables in streams where Staurophora brantii occurs suggest that it prefers fresh alkaline waters with somewhat elevated concentrations of electrolytes, particularly sodium and sulfate. The most frequently co-occurring associates of Staurophora brantii are largely mobile, epipelic taxa that prefer elevated concentrations of dissolved solids.

Size Range, µm3

1001-10000
Motility

Moderately motile
Attachment

Unattached
Habitat

Benthic
Colony

Solitary
Waterbody

Inland
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Credit: Loren Bahls

Valve view of uncleaned Staurophora brantii showing single lobed chloroplast, nucleus (n), and large lenticular pyrenoid (p). LM, 400X, scale bar = 10 μm.

Original Description

Cells solitary, lying mostly in valve view, within a laminated mucilage capsule (Fig. 1). One lobed plastid with a large lenticular pyrenoid positioned against the girdle opposite the nucleus (Figs. 1, 2). Valves elliptic-lanceolate to rhombic-lanceolate, apices broadly rounded and somewhat protracted (Figs 5–10). Valve face curved in transapical section, merging gradually into the mantle (Figs 19, 20), mantle shallower near the ends (Fig. 20). Valve length 38–48 μm; valve width 9–12 μm. Raphe sternum narrow, somewhat thickened and slightly elevated at the central nodule (Fig. 20). Overlapping girdle elements bear longitudinal rows of small round poroids (Fig. 23). Raphe straight, filiform. External proximal raphe endings bordered by lips and lying in spathulate grooves (Figs 24, 25); terminal fissures strongly curved, opening toward the secondary side of the valve (Fig. 22). Internal proximal raphe endings bent in the same direction (Fig. 27); terminal fissures end in helictoglossae (Fig. 26). Axial area narrow, linear, widening slightly near the central area. Central area a transverse fascia, wider toward the margins and with a few shortened striae on one or both sides. Only the ends of the longest of these short striae are visible in valve view, making them appear to be more widely spaced than other striae (Fig. 20). Striae radiate and uniseriate, 18–24 in 10 μm (14 in 10 μm, initial valve, Fig. 10), but more concentrated toward the poles. Striae composed of small round areolae.