• Category
  • Length Range
    30-89 µm
  • Width Range
    16-26.5 µm
  • Striae in 10 µm
  • Reported As
    Cymbella muelleri ((Patrick and Reimer 1975, pl.7, fig. 1))



Valves are strongly dorsi-ventral. The dorsal margin is broadly arched, while the ventral margin is expanded. The valve apices are acute. The axial area is relatively broad in the central part, narrowing at the valve ends. The raphe branches have a slight arch towards the ventral margin. Each raphe branch is positioned nearly centrally within the axial area. Proximal raphe ends are slightly expanded and dorsally deflected. Distal raphe ends curve slightly to the dorsal margin, but are deflected ventrally near the valve apices. The dorsal striae are divergent. Externally, the rows of dorsal areolae closest to the central area are oval, and become lineolate, the length of the lineolae becoming greater towards the dorsal margin. Dorsally, central striae number 10 in 10 μm and distal striae number 5 in 5 μm. Ventrally, central striae number 8 in 10 μm, and distal striae number 6 in 5 μm. The density of areolae within a central, dorsal stria is 7-8 in 5 μm. The striae continue continue onto the mantle, but stop short of the valve margin. Internally, the striae are lineolate and positioned between thickened internal costae. The proximal raphe ends are deflected dorsally at a 90° angle. Distally, the raphe ends at a terminal nodule. A single chloroplast possesses two lobes and ventral fold.

Note that this diatom has long been reported as Cymbella muelleri Hustedt, as shown in Patrick and Reimer (1975). The species, however, was described from Africa by Hustedt. Examination of the type illustrations showed that the African taxon does not share an affinity with the taxon illustrated by Patrick and Reimer (Spaulding et al. 2010).


Colonies of Encyonema reimeri grow within mucilagious tubes.

12  Planktothrix And  Encyonema 1
Credit: Kalina Manoylov
Cells of growing within a mucilage tube, its typical growth habit. Cells of the blue-green alga Planktothrix surround the diatom colony.
Credit: Nick Schulte and the 2015 Iowa Lakeside Lab class
Sexual reproduction in E. reimeri may follow Geitler's Type IA1a (Fig C, D) or possibly Type IC (Fig. B). Two parental cells are paired ventral to ventral within a common copulation mucilage that is further covered in organic and mineral debris (Fig. A). Each parental cell appears to produce two gametangia that are released into the mucilage for pairing. The two resultant auxospores undergo expansion and silicification to become initial cells, but it was unclear if there was a distinct orientation (parallel or non-oriented) to the parental cells.
Credit: Nick Schulte and the 2015 Iowa Lakeside Lab class
Size range of population of E. reimeri collected from in the wave zone near Triboji Beach, West Lake Okoboji, Iowa on May 26, 2015.
Lw Reimeri
Credit: Nick Schulte and the 2015 Iowa Lakeside Lab class
Analysis showed E. reimeri ranges in size from 38 to 89 µm in length and 16 to 26.5 µm in breadth; these measurement extended the reported size metrics (L 30-75 µm, B 17-22 µm; Spaulding et al. 2010). Shorter valves had less attenuated ends and less tumid ventral inflations. There is a positive relationship between valve length and breadth (Fig. 2), and a weak negative relationship between striae density and cell size.

Original Description

Valvulae sunt valde dorsiventrales. Dorsualis margo ample arcuata est, sed ventralis margo inflatosa est. Valvulae longitudo 30-75 μm est; amplitudo 17-22 μm est. Valvulae terminationes acutae sunt. Axialis superficies est relative ampla in centrali valvula et astringitur in extrema valvula. Suturae ramificationes levem habent arcum ad ventralem marginem. Unaquaeque suturae ramificatio posita est fere centrali positione intra axialem superficiem. Suturae extrema proxima leviter sunt expansi et dorsualiter deflexi. Suturae extrema distalia suturae curvaminis leviter inflectuntur marginem ad dorsualem, sed ventraliter sunt deflexa prope valvulae apices. Dorsuales striae sunt in diversum vergentes. Externe, primae series sunt ovales fiuntque lineolatae, maiorque fit lineolatarum longitudo ad dorsualem marginem. Dorsualiter, striae numeris 10 sunt in 10 μm; centraliter sunt 9 in 10 μm. Striae continuantur super dorsualem marginem valvulae. Interne, striae lineolatae sunt et positae intra cubicula, cum internis costis super dorsualem marginem spissatae. Suturae extrema proxima dorsualiter sunt deflexa angulo 90 graduum. Distaliter, sutura terminali nodulo finit. Chloroplasti duas habent auriculas, ventrali plica.

  • Author
    S.A.Spauld., Pool and S.Castro 2010
  • Length Range
    30-75 µm
  • Width
    17-22 µm
  • Striae in 10µm

Original Images

Encyonema reimeri HOLOTYPE
Original text and images reproduced with permission by Proceedings of the Academy of Natural Sciences of Philadephia.


Jun 20, 2024 - Extension of size range

Prior to this date, length was documented as 30-75 µm and width as 17-22 µm. These values were revised based on the 2015 diatom class observations. which were presented in a poster at the North American Diatom Symposium (Schulte et al. 2015). See AUTECOLOGY tab for details. - S. Spaulding

Cite This Page

Spaulding, S. (2010). Encyonema reimeri. In Diatoms of North America. Retrieved June 20, 2024, from https://diatoms.org/species/encyononema_reimeri


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