Diatoms of North AmericaDiatoms of North America

Entomoneis ornata

(J.W.Bailey) Reimer 1975

Entomoneis Ornata Guide
  • Category
    Surirelloid
  • Length Range
    71-93 µm
  • Width Range
    23-43 (girdle view) µm
  • Striae in 10 µm
    20-24

Identification

Entomornata1 Entomornata2 Entomornata3 Entomornata4 Entomornata5 Entomornata6 Entomornata7
View image metadata
Entomoneis ornata SEM1 Entomoneis ornata SEM2

Description

Frustules almost always come to rest in girdle view, a view which is dominated by highly arched bilobate keels. The keels are strongly torsioned so that only one lobe is in focus at one time. In complete frustules in girdle view, diagonally opposing lobes lie at approximately the same level of focus. Lobes are flattened in large specimens and more rounded in smaller specimens. Several girdle bands are present, each with a linear series of short transverse dashes that appear to cross at mid-valve. The junction line between the valve and the keel is marked by a series of prominent and irregularly shaped bulges or swellings. Striae on the valve face continue onto the keel. Areolae within a stria on the valve face are very fine and number 26-30 in 10 µm. Areolae within a stria on the keel are more prominent and number 14-20 in 10 µm.

Autecology

This taxon is broadly distributed (Patrick and Reimer 1975), and has been reported with light micrographs from Alaska (Foged 1981), the Rocky Mountains, and Great Plains (Bahls 2023). This taxon has been documented in Montana from 23 lakes, marshes, large rivers, and small creeks, both east and west of the Continental Divide.

In the Great Lakes National Parks (Edlund et al. 2009, 2011, 2012, 2013), this taxon is rare (0.1-1% abundance) at Voyageurs ( Ek, Peary, and Mukooda lakes), Pictured Rocks (Grand Sable Lake), and Isle Royale (Richie and Ahmik lakes).

This taxon is known to occur in lakes, sloughs, wetlands, rivers and prairie streams (Bahls 2023). It is reported to prefer cool alkaline waters of moderately high conductivity and nutrient content (Bahls 2023). Common diatom associates of this taxon include Gomphonema turgidum, Gomphonema coronatum, Placoneis explanata, Cavinula jaernefeltii, Stauroneis heinii, and Nitzschia obtusa. Like E. alata, this taxon prefers waters with elevated concentrations of sodium and sulfate.

Several research groups consider this taxon an indicator organism and published regional environmental optima and tolerances including:

Bahls (2023): Conductivity - 2208 µS/cm, pH - 8.1, Temperature - 16.9°C, Total Nitrogen - 1.32 mg/L, Total Phosphorus - 65 µg/L.

Kintla Lake Long Knife Peak
Credit: Loren Bahls
Kintla Lake, Glacier National Park, Montana: home of Entomoneis ornata.

Original Description

AMPHIPRORA ORNATA, B. Pl. 2, figs. 15 and 23. Small, deeply constricted, ends truncated and rounded, sides marked with a longitudinal row of undulations or pinnulæ, as in Surirella. Often contorted. The ruffle-like rows of pinnulæ distinguish this species from all others. It probably has minute striæ also, but I did not have an opportunity to examine with high powers. Hab. Withlacoochee River, where it is crossed by the road from Pilatka to Tampa, Fa.

  • Basionym
    Amphiprora ornata
  • Author
    J.W.Bailey 1851

Original Images

Entomoneis ornata orig illus
Entomoneis Ornata Orig Descr

Citations & Links

Citations

Links

Updates

Feb 05, 2026 - Addition of Autecology and SEMs

From 2012 until 2026, the autecological information on this taxon page was limited. As of this update, SEMs and information on ecology, biogeography, and environmental optima have been added. - Lane Allen and Mark Edlund

Cite This Page

Bahls, L., Edlund, M., Allen, L. (2012). Entomoneis ornata. In Diatoms of North America. Retrieved March 25, 2026, from https://diatoms.org/species/48223/entomoneis_ornata

Responses

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