• Category
  • Length Range
    19–56 µm
  • Width Range
    6–9 µm
  • Striae in 10 µm
  • Reported As
    Surirella sp. [cf. S. angusta Kützing 1844] (Antoniades et al. 2008, pg. 296, Pl. 79, Figs 1-5, Pl. 132, Figs 7-9))



Valves are isopolar, or barely heteropolar, linear with cuneate apices and 4.3–6.4 length-to-width ratio (in very small specimens, down to 2.7). The most peculiar feature of this taxon is the massive craticula-like structure, in which the median area and transverse costae are internally thickened. The thickening occurs on the inner valve surface, and is clearly visible in LM. In some specimens, especially small ones, the thickened median area can be wider and less prominent, thus not as prominent as in longer specimens. Costae are arranged more or less regularly, and there are usually 3–6 striae in between each pair of costae (1–6 in small specimens). Density of costae/fibulae is 43–61 in 100 μm (up to 70 in 100 μm in small specimens). Median area is very narrow, but appears much wider when focusing on the internal valve surface. Striae are parallel, slightly radiating toward the apices. Visible under SEM, striae are mostly triseriate (2–4 rows of areolae in 1 stria) and are externally separated by ridges. Each 4th or 5th ridge is depressed (corresponding to an internal costa) below the valve face level. Frustules are rectangular in girdle view with visible costae in LM.


Surirella arctica was encountered in small freshwater pools and seepages around Driftwood, North Slope, in the northeastern Alaska, USA (including the type locality), with the following water characteristics: pH 7.4–8.4, water temperature 7°–12° C, alkalinity 310 ppm (as CaCO3), hardness 350 ppm (as CaCO3), chloride 200 ppm, and total Fe 0.06 ppm (Patrick & Freese 1961). This taxon was also found in Ellef Ringnes Island, Canada. Surirella arctica probably occurs in other freshwater localities in the high Arctic of North America (north of 68°N latitude).

Original Description

Valva lineari apicibus rotundatis, cuneatis. Axe apicali designato linea, clara, angusta. Alis 5-6 in 10 μ, angustis. Summa valva striata. Striis, 22-30 in 10 μ. Longitudo, 26-49 μ. Latitudo, 6-8 μ.

Valve linear with wedge-shaped, rounded apices. Apical axis marked by a clear narrow line. Alae 5-6 in 10 μ, narrow. Surface of valve striated. Striae, 22-30 in 10 μ. Length, 26-49 μ. Breadth, 6-8 μ. This variety is distinguished from the nominate variety, Surirella terryi Ward var. terryi, by the shape of the ends of the valve and the number of the alae. Specimen illustrated.--Station 109 (A-G.C. 8225B). Holotype. Type locality.--Alaska, Sec. Jud. Div., Driftwood. Coll. L. R. Freese, 1 August 1951.

  • Basionym
    Surirella terryi var. arctica
  • Author
    R.M.Patrick and Freese 1961
  • Length Range
    26–49 µm
  • Width
    6–8 µm
  • Striae in 10µm

Original Images

Surirella Terryi Var Arctica Orig Image  Pf1961
Surirella Terryi Var Arctica Orig Image  Vp2014
Surirella Terryi Var Arctica Orig Descript  Pf1961

Cite This Page

Veselá, J. (2017). Surirella arctica. In Diatoms of North America. Retrieved May 18, 2024, from https://diatoms.org/species/surirella_arctica


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