• Category
  • Diameter
    4-12 µm
  • Width Range
    9-18 µm
  • Striae in 10 µm



Frustules are cylindrical and form colonies. Valves are 4-12 µm in diameter, with a mantle height of 9-18 µm. The ratio of the mantle height to valve diameter is greater than 1. The mantle has straight sides and the valve face is strongly concave or convex. Rows of mantle areolae are straight, 5.5-9 in 10 µm, with 5-10 round areolae in 10 µm. The height of the collum is approximately 1/3-1/4 of the mantle height. The valve face is covered by areolae. The spines are thin, often bifurcated, and irregular in shape. The ringleiste is solid, broad and shallow.


Original Description

Frustules cylindrial, linked into short straight or curved chains; valves 6-10 μm in diameter, mantle height 10-17 μm, ratio height/diameter 0,8-1,5, varies not only throughout the division cycle, but also between sibling valves and even between valves of a single frustule (fig. 72). Outer and inner mantle lines straight and parallel; discus distinctly convex (fig. 76) or concave (fig. 79, in sibling valves, convex and concave disci fit into each another); pseudosulcus a broad but flat furrow. Cell wall thick; linking spines short; separating spines not observed, the broad collum bears on its inside a very broad Ringleiste (figs. 73, 74). The disci have varied patterns of medium-seized areolae, sometimes being dispersed and irregularly distributed (figs. 75, 79), in completely areolated disci the areolae sometimes arranged in tangential rows. Nearly every pervalvar mantle rib bears a very small, somewhat irregularly shaped linking spine with bifid anchors (figs. 76-78). The mantle areolae vary in size (fig. 76), are very large and appear pearl-like in the LM (figs. 71, 72). SEM reveals very irregular areolae foramina (figs. 76-78). The pervalvar rows (6-9/10 μm) run parallel or slightly oblique to the pervalvar axis. The areola arrangement here is somewhat irregular with the consequence that transverse rows are either absent (figs. 71, 78) or indistinct (figs. 72, 76).

  • Author
    Krammer 1991
  • Length Range
    6-10 µm
  • Width
    10-17 µm
  • Striae in 10µm

Original Images

Orig Ill  Aucrass 1
Orig Descr  Aucrass 2


Jul 22, 2018 - EMAP distribution removed

Aulacoseira crassipunctata was reported from 2 sites in the western EMAP survey, 1998SIDFB124 and WIDP99-069. Potapova examined 2 slides from site WIDP99-0697, but failed to confirm the presence of A. crassipunctata. The EMAP distribution and data plots were removed from this page. A fragment of the fossil A. canadensis may have been present, misidentified as A. crassipunctata. - S. Spaulding

Cite This Page

Potapova, M. (2010). Aulacoseira crassipunctata. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/aulacoseira_crassipunctata


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