Brachysira neoacuta
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Category
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Length Range31-51 µm
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Width Range6.5-9 µm
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Striae in 10 µm24-26
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Reported AsAnomoeoneis serians var. acuta (Patrick & Reimer 1966, pg. 378, pl. 33, fig. 2)
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ContributorPaul Hamilton - Dec 2010
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ReviewerSarah Spaulding - Feb 2011
Identification
Description
Valves are rhombic-lanceolate with straight margins and acute, narrow, rounded apices. Striae are radiate throughout; striae along the center contain two to five areolae and striae at the apices with a single areola. The axial area is straight. The central area is asymmetrically rounded, barely wider than the axial area. The raphe is positioned within two ribs on the external valve face. The ribs terminate within the central area and at the apices. The raphe is straight, curving weakly at the proximal and distal ends.The proximal raphe ends are straight and the distal fissures have T-shaped endings. Areolae are elongated box-like slits with rounded ends, oriented to the transapical axis. Spaces between the areolae give the appearance of longitudinal undulations. A thickened rib is present along the valve margin (except at the apices) separating the valve face from the mantle. The mantle possesses a single row of elongated pores. One or two Voigt discontinuities are present on the secondary side of each valve. Valve face papillae, if present, are small.
In SEM, the internal proximal raphes terminate at small helictoglossae. Areolae are covered internally by hymenes.
Original Description
Valvae lanceolatae apicibus acute rotundatis marginibus ad apices modice concavis (non rectis nec convexis), 40-65 μm longae, 6-9 μm latae. Raphe modice arcuata fissuris internis/externis minime lateralibus. Area axialis modice angusta, area centralis satis parva (numquam ampla) plusminusve rhombica ad instar. Striae transapicales magnopere radiantes usque ad apices, 24-26 in 10 μm. Inordinatio Voigtii distincta. Structurae submicroscopicae: Papillae in fronte adsunt. Alia signa typica submicroscopica vide in Fig. 18:3,4.
Schalen im Umriβ ähnlicher B. wygaschii als B. serians s. str., aber schmaler lanzettlich mit länger vorgezogenen, noch spitzer gerundeten Enden. Die Schalenränder vor den Enden sind schwach konkav und nicht konvex. Länge 40-65 μm, Breite 6-9 μm. Raphe, Axial- und Zentralarea ähnlich B. wygaschii, Zentralarea tendenziell etwas kleiner. Streifen durchweg stark radial, 24-26/10 μm, Voigt-Diskordanz deutlich. REM: Weitgehend Übereinstimmung mit B. wygaschii, aber mit kleinen Wärzchen auf der Schalenoberfläche.
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AuthorLange-Bert. in Lange-Bert. and Gerd Moser 1994
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Length Range40-65 µm
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Width6-9 µm
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Striae in 10µm24-26
Original Images
Citations & Links
Citations
Links
Cite This Page
Hamilton, P. (2010). Brachysira neoacuta. In Diatoms of North America. Retrieved December 21, 2024, from https://diatoms.org/species/45379/brachysira_neoacuta
Responses
The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Brachysira neoacuta from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:
ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.
Brachysira neoacuta
- Valves narrowly lanceolate
- Striae strongly radiate at the center
- Areolae distinctly rectangular
- Distal raphe unilaterally curved
Valves are narrowly lanceolate, with a length to width ratio of approximately 5:1. The striae are strongly radiate at the center, becoming parallel at the apices. Irregular striae are present near the central area. Areolae are distinctly rectangular and range 2-4 per stria. The distal raphe is distinctly unilaterally curved.