• Category
  • Length Range
    54-71.6 µm
  • Width Range
    11.1-12.5 µm
  • Striae in 10 µm
  • Reported As
    Pinnularia nodosa var. constrictum f. truncata (Camburn and Charles 2000, pg. 92, Pl. 26, Fig 3-4)



Valves are linear and triundulate. Th central undulation is more narrow than the distal undulations. Apices are roughly half the breadth of the distal undulations. The axial area is wide, undulate and about one half the valve width. The central area is often a small, asymmetric fascia but is indistinct in some valves. The valve face is distinctly mottled in LM. The striae are marginal, parallel to barely radiate at center valve, becoming convergent at the apices. The raphe is lateral and almost straight, with proximal ends deflected to one side.

Note that Pinnularia nodosa var. constrictum f. truncata is a heterotypic synonym of P. scotica. Although P. nodosa var. constrictum f. truncata was published earlier, P. scotica’s subsequent description at the species level takes precedence.


Pinnularia scotica was described from Scotland and has been reported from central Europe (Krammer 2000) and Bulgaria (Isheva et al. 2016). This species has been reported from Idaho (Bahls 2009) and confirmed in our work from lakes in Connecticut and Maine.

Original Description

56. Pinnularia scotica nov. spec.

Synonyms: Pinnularia nodose morphotype 3 sensu Krammer 1992a, p.82; Pinnularia nodose sensu Krammer 1992b, fig.13 7-11; Pinnularia subnodosa sensu Hartley 1996, fig. 233 5 (left three figs).

Type locality: Elchies, Scotland, leg. Gregory, slide IX-37-B15 VH.

Valves linear, bindulate with concave sides, or weakly triundulate with equal undulations or sometimes smaller or wider middle undulation, ends broadly rostrate up to capitate with obtusely rounded apices, smaller than the valve body length 50-90 μ, breadth 11-13 μm. Raphe narrow, slightly lateral, outer fissure deflected to one side, in the middle terminating in tear-shaped central pores, distal fissures ?-shaped. Axial area very broad, linear, striae marginal, central area a small fascia, sometimes a semifascia. Striae 9-10/10 μm, parallel up to slightly radiate in the middle, becoming slightly convergent in the distal striae.

Distribution Some recordsrecords in central Europe (Franken). Diverse places in Scotland (Elgin, Elchies, Premnay Peat) however infrequent.

The outline with obtusely rounded apices, a broad axial area and the small fascia distinguish this taxon well from similar forms. To date this taxon was connected frequently with the different P. subnodosa Hustedt (e.g. HARTLEY 1996, fig. 233:5).

  • Author
    Krammer 2000
  • Length Range
    50-90 µm
  • Width
    11-13 µm
  • Striae in 10µm

Original Images

Pinnularia Scotica Orig Illus
Pinnularia Scotica Orig Desc

Cite This Page

Polaskey, M., Camp, A. (2018). Pinnularia scotica. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/pinnularia-scotica


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