• Category
  • Length Range
    5-17 µm
  • Width Range
    3-6 µm
  • Striae in 10 µm



Valves are lanceolate to elliptic with rounded or slightly drawn-out apices. The raphe valve has a linear axial area and central area that is variable in shape - from transversely rectangular to elliptic. The rapheless valve has a linear-lanceolate axial area that slightly widens in the center. The asymmetric central area on rapheless valve contains a cavum on the internal valve surface. The raphe is straight, with expanded external proximal ends. Terminal raphe fissures are curved to the secondary side of the valve. The striae are multiseriate and radiate throughout both valves.

Original Description

Valvae ellipticae finibus plerumque non protractis obtuse ad late rotundatis nonnumquam paulo protractis numquam abrupte rostrato-protractis. Longitudo 4-36 μm, latitude 2,5-6,5 μm. Raphovalva ab Achnanthes lanceolata ssp. lanceolata non differt. Areovalva nunc autem differt constructione particulare »cavum tectum« dictum nec »sinus« i.e. caverna aperta. Itaque ssp. frequentissima singulari complexione signorum typicorum est distinguenda subspeciebus lanceolata, rostrata, dubia, biporoma, robusta, apiculata, lanceolatoides

  • Basionym
    Achnanthes lanceolata subsp. frequentissima
  • Author
    Lange-Bert. 1993
  • Length Range
    4-36 µm
  • Width
    2.5-6.5 µm

Original Images

Orig Ill  Plfr
Orig Descr  Plfr

Cite This Page

Potapova, M. (2010). Planothidium frequentissimum. In Diatoms of North America. Retrieved May 29, 2024, from https://diatoms.org/species/planothidium_frequentissimum


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