• Category
  • Length Range
    28–85 µm
  • Width Range
    6.7–9.0 µm
  • Striae in 10 µm
    8.0–12 in the valve center, 11–16 at the ends.



Valves are weakly arcuate. The dorsal margin is convex and has 3 - 5 undulations. In some (especially smaller) specimens, the dorsal undulations are weakly expressed. The ventral margin often has a central inflation. The apices are rounded and slightly recurved to the dorsal side. Helictiglossae are prominent near the apices. The raphe is apparent in few specimens;, the raphe curves around the apical margin and along the dorsal valve. Transpical striae are distinctly punctate and parallel, becoming radiate at the apices. A small sternum is present, near the ventral margin. Areolae are distinct in LM, 24-26 in 10 µm.

This species is presented in the broader concept of Hoffman et al. (2013), including the variety E. pectinalis var. undulata, because populations included a range of dorsal swelling. Other authors (e.g., Patrick and Reimer 1966, Lange-Bertalot et al. 2011) recognize E. pectinalis and E. pectinalis var. undulata as separate taxa.


Eunotia pectinalis is a cosmopolitan (Foged 1981, Lange-Betalot et al. 2011) species found to be rare (Camburn et al. 1978, Furey et al. 2011) to common (Siver et al. 2005) in abundance. The species is acidophilic and has been found living in the epiphyton, epidendron, epilithon, and metaphyton of oligotrophic to eutrophic lakes ( Camburn et al. 1978, Siver et al. 2005, Siver and Hamilton 2011), streams (Foged 1981, Fallu et al. 2000, Furey et al. 2011), and wetlands (Burge 2014). Specimens we examined were found living among E. bilunaris, E. formica, and E. metamonodon as well as species of Gomphonema, Navicula, and Pinnlaria in cypress-tupelo wetlands of Arkansas with the following water chemistry: 22.2–27.4 ºC, 5.59–7.37 pH, DO 0.05–7.65 mg/L, Specific conductance 71–834 µS, 8.1–321 NTU, NH3-N 0.08–13.03 mg/L, NO3-N 0.01–0.3 mg/L, NO2-N <0.01–0.5 mg/L, TP 0.1–3.9 mg/L, PO4-P 0.02–2.08 mg/L (Burge 2014).

Original Description

  • Basionym
    Himantidium pectinalis
  • Author
    Kütz. 1844

Original Images

Eunotia pectinalis orig illus
Himantidium Pectinalis

EMAP Assessment

EMAP Distribution

Eunotia Pectinalis   Mùller   Rabenhorst 20
Map 20

Response Plots

Eunotia Pectinalis

Citations & Links



Cite This Page

Burge, D, and Edlund, M. (2015). Eunotia pectinalis. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/eunotia_pectinalis


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