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Encyonema triangulum

(Ehrenb.) Kütz. 1849      Category: Asymmetrical biraphid
BASIONYM: Gloeonema triangulum Ehrenb. 1845
SYNONYM(S): Cymbella triangulum (Ehrenb.) Cleve 1894 
REPORTED AS: Cymbella triangulum (Patrick & Reimer 1975) 

Encyonema temperei


Encyonema yellowstonianum

LM scalebar = 10 µm = 40 pixels.


Contributor: Loren Bahls - January 2012
Length Range: 37-72 µm
Width Range: 16-23 µm
Striae in 10 µm: dorsal side: 8-10 center, 11-12 ends; ventral side: 9-12 center, 12-14 ends


Valves are elliptic-lanceolate and moderately asymmetric to the apical axis, with smoothly convex dorsal and ventral margins. The apices are and acute and apiculate. The axial area is variable in width, 3-6 times wider than the raphe. The central area is only slightly wider than the axial area. The raphe is lateral and arched, becoming concave toward the dorsal side. Proximal raphe ends are slightly expanded and deflected dorsally; distal raphe ends are recurved ventrally. Striae are slightly radiate, becoming parallel and then convergent at the apices, especially on the ventral side. The central one or two striae on the dorsal side are often slightly longer than adjacent striae. Areolae are very coarse and number 8-10 in 10 µm.

Original Description

Basionym: Gloeonema triangulum
Author: Ehrenb. 1845
Length Range: µm
Striae in 10 µm:

Original Description

GLOEONEMA? triangulum: Gl. corpusculis naviculaceis utrinque acutis, dorsi gibbere altiore inaequalibus et in formam a latere conspicuam triangularem abeuntibus. Diam. Naviculae 1/66”’. Vivum in Niagara. Tubulos continuos non vidi, sed Gloeonemati paradoxo associatum vidi, cujus tubuli aderant cum singnlis eodem modo sparsis corpusculis.

Original Images

Cite This Page:
Bahls, L. (2012). Encyonema triangulum. In Diatoms of the United States. Retrieved May 22, 2018, from

Species: Encyonema triangulum

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Ehrenberg, C.G. (1845). Neue Untersuchungen über das kleinste Leben als geologisches Moment. Mit kurzer Charakteristik von 10 neuen Genera und 66 neuen Arten. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlichen Preussischen Akademie der Wissenshaften zu Berlin, for 1845: 53-88.

Krammer, K. (1997). Die cymbelloiden Diatomeen. Eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema. Bibliotheca Diatomologica 36: 1-382.

Krammer, K. and Lange-Bertalot, H. (1986). Bacillariophyceae. 1. Teil: Naviculaceae. In: Ettl, H., J. Gerloff, H. Heynig and D. Mollenhauer (eds.) Süsswasserflora von Mitteleuropa, Band 2/1. Gustav Fisher Verlag, Jena. 876 pp.

Kützing, F.T. (1849). Species Algarum. Lipsiae. F.A. Brockhaus, 922 pp.

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Silva, W.J., Jahn, R., Ludwig, T.A.V. and Menezes, M. (2013). Typification of seven species of Encyonema and characterization of Encyonema leibleinii comb. nov. Fottea, Olomouc 13(2): 119–132.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Encyonema triangulum CAS

NCBI Genbank Taxonomy

Encyonema triangulum NCBI

North American Diatom Ecological Database (NADED)

NADED ID: 110016

Autecology Discussion

Encyonema triangulum is widely distributed in hardwater streams and lakes throughout the United States (Patrick & Reimer 1975). There are 39 records of this species in the Montana Diatom Collection from the Northwestern United States. Here the mean pH is 7.4 and the mean specific conductance is 2261 μS/cm (see table below for other variables). Common diatom associates of E. triangulum are Navicula subrhynchocephala, Navicula namibica, Navicula germainii, Nitzschia sigma, Plagiotropis lepidoptera var. proboscidea, Tryblionella gracilis, and Navicula amphiceropsis.


School Section Lake, Lake Metigoshe State Park, Bottineau County, North Dakota: home of Encyonema triangulum.

Credit/Source: Loren Bahls

Abundance-weighted means for selected water quality variables measured concurrently with the collection of samples that contain Encyonema triangulum.

Credit/Source: Montana Diatom Database

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Encyonema triangulum

EMAP Response Plots

Encyonema triangulum

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.