Diatoms of North AmericaDiatoms of North America

Brachysira neoacuta

Lange-Bert. in Lange-Bert. and Gerd Moser 1994

Brachysira Neoacuta
  • Category
    Symmetric Biraphid
  • Length Range
    31-51 µm
  • Width Range
    6.5-9 µm
  • Striae in 10 µm
    24-26
  • Reported As
    Anomoeoneis serians var. acuta (Patrick & Reimer 1966, pg. 378, pl. 33, fig. 2)

Identification

Bracysira neoacuta LM7 Bracysira neoacuta LM6 Bracysira neoacuta LM5 Bracysira neoacuta LM4 Bracysira neoacuta LM3 Bracysira neoacuta LM2 Bracysira neoacuta LM1
View image metadata
Brachysira neoacuta SEM1 Brachysira neoacuta SEM2 Brachysira neoacuta SEM3

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.

Autecology

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.

  • Author
    Lange-Bert. in Lange-Bert. and Gerd Moser 1994
  • Length Range
    40-65 µm
  • Width
    6-9 µm
  • Striae in 10µm
    24-26

Original Images

Brachysira neoacuta orig illus
Brachysira neoacuta orig descr

Cite This Page

Hamilton, P. (2010). Brachysira neoacuta. In Diatoms of North America. Retrieved April 19, 2024, from https://diatoms.org/species/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.