• Category
  • Length Range
    9-25 µm
  • Width Range
    4.8-7.0 µm
  • Striae in 10 µm
  • Reported As
    Planotidium haynaldii (Lange-Bertalot 1999)
    Achnanthes lanceolata var. haynaldii (Patrick and Reimer 1966)



Valves are lanceolate to elliptic-lanceolate with capitate apices. Specimens at the small end of the size range are nearly elliptic. The striae are multiseriate and radiate throughout both valves.

The raphe valve has a linear axial area. The central area varies in shape from transversely rectangular to elliptic. The raphe is straight with expanded external proximal ends. The terminal raphe fissures are curved to the secondary valve side.

The rapheless valve has a linear-lanceolate axial area that slightly widens in the center. The central area is asymmetric and contains a rimmed depression on the internal valve surface.

Note that this page was originally posted as P. haynaldii (Schaarschm.) Lange-Bert. In 2014, Wetzel et al. examined the type material of P. haynaldii. They found that P. haynaldii differs from the Northern Hemisphere species P. amphibium. Although the name was widely applied, we now know that P. haynaldii has only been verified in South America.

Planothidium amphibium is common in the Northern Hemisphere.


Original Description

  • Author
    C.E.Wetzel, Ector and L.Pfister 2014
  • Length Range
    11-21 µm
  • Width
    5-6 µm
  • Striae in 10µm

Original Images

Plamphib Or D2
Plamphib Or Ill
Plamphib Or D1


May 20, 2024 - Change of name

From 2011 to March 2020, this taxon appeared under the name Planothidium haynaldii (Schaarschm.) Lange-Bert. It was updated to conform to Wetzel et al. 2014. Note that the previous version of this page followed the concept of Achnanthes lanceolata var. haynaldii of Patrick and Reimer (1966) and many other floras. - M. Potapova

Cite This Page

Potapova, M. (2011). Planothidium amphibium. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/planothidium_amphibium


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