• Category
  • Length Range
    26.0-32.8 µm
  • Width Range
    6.5-7.6 µm
  • Striae in 10 µm
  • Synonyms
    Parlibellus protracta (Grunow) Witkowski, Lange-Bert. and Metzeltin 2000
    Placoneis protracta protracta (Grunow) Mereschk. 1903



Valves are linear to linear-lanceolate with rostrate, rounded ends. Striae are weakly radiate to parallel at the apices. Striae are less dense in the middle third of the valve. Areolae are visible in less dense striae. The axial area is narrow and expands to a small, elliptic central area. The raphe is straight, with expanded proximal ends. Shallow, curved pseudoseptae are present at both apices.


Prestauroneis protracta has a broad demonstrated range in North America. US Geological Survey samples collected from western Oregon and North Carolina contain this taxon (Pacific Northwest Regional Survey, 2015). In the Pacific Northwest, P. protracta co-occurs with the smaller but similar P. protractoides. Prestauroneis protracta is also encountered across Europe, from the British Isles (Mann 1988) to Poland (Żelazna-Wieczorek et al. 2009) and Serbia (Andrejić et al. 2012).

Original Description

N. (Crucicula var.?) protracta Grun. Linear länglich, mit breiter borgezogener stumpf abgerundeter Spitze. Structur ähnlich wie bei N. Crucicula, Querstriefen 18-21 in 0,01 mm., die mittelsten etwas weiter. Lange 0,022-0,035 mm., Schalenbrete 0,008-0,010 mm. Häufig in schwach salzigem Wasser und Salinen des Binnenlandes. Taf. II, Fig. 38. 900/1.

  • Basionym
    Navicula (Crucicula var.?) protracta
  • Author
    Grunow in Cleve and Grunow 1880
  • Length Range
    22-35 µm
  • Width
    8-10 µm
  • Striae in 10µm

Original Images

P Protracta Orig Desc Plate
P Protracta Orig Desc Text

Cite This Page

Bishop, I. (2017). Prestauroneis protracta. In Diatoms of North America. Retrieved June 21, 2024, from https://diatoms.org/species/prestauroneis_protracta


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Prestauroneis protracta 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.