• Category
  • Length Range
    5-17 µm
  • Width Range
    4.5-6.2 µm
  • Striae in 10 µm
    24-34 in center of raphe valve, 20-25 in center of rapheless valve, up to 45 at apices
  • Synonyms
    Stauroneis exilis Kütz. 1844
    Achnanthes exigua Grunow in Cleve and Grunow 1880
    Achnanthidium exiguum (Grunow) Czarnecki 1994
  • Reported As
    Achnanthes exigua var. heterovalvata (Krasske 1923)
    Achnanthidium exiguum var. heterovalvum ((Krasske) Czarnecki 1994)

Identification

Description

Valves are linear-elliptic to elliptic-lanceolate with narrowly capitate, subcapitate, rostrate, or subrostrate apices. Larger valves are sometimes slightly constricted in the middle. Both raphe and rapheless valves have a narrow slightly sigmoid axial area.

The raphe valve has a distinct fascia that is often slightly wider on one side. The rapheless valve has a small, transapically rectangular, often asymmetric, central area. The raphe is straight, but deflected to opposite sides near the apices, with terminal raphe fissures strongly curved to opposite sides. The external proximal raphe ends are simple, located in slight “pin-hole” depressions, giving the appearance that they are expanded. Internally, the central raphe ends curve toward opposite sides. The striae are radiate on both valves, but almost parallel at the apices. The raphe valve has 24-34 striae in 10 µm in mid-valve, up to 40-45 in 10 µm at the apices.

The raphless valve has 20-25 striae in 10 µm at mid-valve and up to 35-40 in 10 µm at the apices. A few very small areolae may be present on the mantle of both valves. Areolae are round or transapically elongated externally, apically elongated internally, ca. 55-70 in 10 µm within the striae.

The variety Achnanthes exiguum var. heterovalvata was described as having a stria density of 34 in 10 µm. Our observations of material from the US, however, show that the nominate variety includes a gradient of stria density from 24 to 34 in 10 µm. We see that the variation of A. exiguum is quite broad, and therefore, consider Achnanthes exiguum var. heterovalvata as a subjective synonym.

The taxon was originally described as Stauroneis exilis Kützing, from the island of Trinidad (1844). It was later renamed as Achnanthes exigua Grunow 1880. Note that Grunow’s epithet for this taxon was a new name, since when he transferred it to Achnanthes, Kützing’s original epithet was already occupied by Achnanthes exilis Kützing 1833.

Czarnecki transferred Achnanthes exigua Grunow to Achnanthidium exiguum (Grunow) Czarnecki 1994 but did not justify the new combination. Later, the taxon was transferred to Lemnicola exigua (Grunow) Kulikovskiy, Witkowski and Plinski 2011. In 2020, Kulikovsky et al. recognized Gogorevia based on molecular and morphological features.

Original Description

St. minutissima, elliptico-lanceolata, breviter rostellata, Long. 1/200´´´

  • Basionym
    Achnanthes exigua
  • Author
    Grunow in Cleve and Grunow 1880
  • Length Range
    11.3 µm

Original Images

Orig Ill  Ahexig
Orig Descr002

Citations & Links

Links

Updates

May 02, 2022 - Transfer from Achnanthidium to Gogorevia

From 2010 until 2022, this taxon appeared on this website as Achnanthidium exiguum (Grunow) Czarnecki 1994. Following Kulikovsky et al. (2020), the transfer to Gogorevia was reflected on the page. - S. Spaulding

Cite This Page

Potapova, M. (2010). Gogorevia exilis. In Diatoms of North America. Retrieved August 11, 2022, from https://diatoms.org/species/gogorevia-exilis

Responses

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