• Category
  • Diameter
    22.1-50.5 µm
  • Striae in 10 µm
    6.4-7.1 based on circumferential density



Frustules are heavily silicified and aligned in short filaments of 2-10 cells adjoined face-to-face by short conical or flattened spines. The spines are regularly spaced along the face-mantle junction. Frustules are 39.7-51.1 µm long in the pervalvar axis. The base of the spines extend onto the mantle and may continue for a short distance onto the valve face. The mantle is broad. In smaller cells, the mantle height is relatively larger. Valves have a flat to slightly convex face. Valves have a small central area with 2-5 carinoportulae, a type of pore specific to the genus Orthoseira. Valve face areolae are arranged in radial striae that end in small furrows formed by adjacent spine bases near the face-mantle junction. Valve face areola density is 14.5-19.3 in 10 µm. The valve mantle has straight pervalvar striae (16.4-19.3 in 10 µm) with areola density 13.5-17.5 in 10 µm. Frustules with a broad cingulum. Girdle bands are variably ornamented with pervalvar rows of fine areolae.

The genus Orthoseira is recognized as needing monographic treatment to resolve the typification, taxonomy, and nomenclature of its common forms—roeseana, dendroteres, dendrophila, tatrica, circularis, americana, epidendron (Houk 1993, 2003, Spaulding and Kociolek 1998), which is complicated by the great morphologic variation within current taxa. Here, we follow the broad concept taxonomy for O. roeseana of Houk (2003).


Orthoseira roeseana is an aerophilic species found on wet walls and moist subaerial habitats. It is found across a broad latitudinal gradient, from small ponds in Alaska (Foged 1981) to subaerial habitats in Ohio (this material and Roemer and Rosowski 1980), the Great Lakes (Stoermer et al. 1999), the Northwest Territories (Sheath and Steinman 1982) and subtropical regions (Spaulding and Kociolek 1998).

6 486 22 1  Ortho Roes 715 A
Credit: M. Edlund
Girdle view of filament, at two levels of focus (Science Museum of Minnesota MBE 825A).
7 708 32 2  Ortho Roes 715 A
Credit: M. Edlund
Girdle view of filament, showing the silica spines that join frustules together (Science Museum of Minnesota MBE 825A).
Orthoseira  Ansp  Gc3441
Credit: S. Spaulding
Low magnification image of a large number of Orthoseira roeseana filaments (Academy of Natural Sciences of Drexel University GC3441).

Original Description

  • Basionym
    Melosira roeseana
  • Author
    Rabenh. 1853
  • Length Range
    20 µm

Original Images

Ortho Roeseana  Rabenhorst 1853 Icon
Ortho Roeseana  Rabenhorst 1853 Descrip

Citations & Links



  • Index Nominum Algarum
  • CAS
  • North American Diatom Ecological Database
    NADED ID: 74001

Cite This Page

Edlund, M, and Burge, D. (2017). Orthoseira roeseana. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/orthoseira_roeseana


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