• Category
  • Length Range
    25-31 µm
  • Width Range
    9.0-12.7 µm
  • Striae in 10 µm



Valves are elliptical-lanceolate with apiculate apices. The raphe valve has a large rhomboid or transversely elliptical central area. The rapheless valve has an asymmetrical central area, expanded on one side to the valve margin. This asymmetrical central area also contains a hood on the internal valve surface. The raphe is straight with expanded external proximal endings. The striae are strongly radiate on the raphe valve and slightly radiate on the rapheless valve. The striae are multiseriate.


Original Description

Valvae elliptico-lanceolatae, 28 μ longae, 10-11 μ latae, apicibus apiculatis. Valva superior ad instar soleae equinae effigiem in medio ostendens, pseudoraphe anguste lanceolata; striis radiantibus, 10-12 in 10 μ. Valva inferior aream axialem angustam et aream centralem rotundatam exhibens; striis validis radiantibus, 10 in 10 μ.

  • Basionym
    Achnanthes lanceolata var. apiculata
  • Author
    R.M.Patrick 1945
  • Length Range
    28 µm
  • Width
    10-11 µm
  • Striae in 10µm

Original Images

Orig Ill  Plapic
Orig Descr  Plapic

EMAP Assessment

EMAP Distribution

Planothidium Apiculatum 40 Copy
Map 40

Response Plots

Planothidium Apiculatum Copy

Cite This Page

Potapova, M. (2010). Planothidium apiculatum. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/planothidium_apiculatum


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