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Melosira undulata

(Ehrenb.) Kütz. 1844      Category: Centric
BASIONYM: Gallionella undulata Ehrenb. 1840

Melosira normannii


Melosira varians

LM scalebar = 10 µm = 20 pixels.


Contributor: Loren Bahls - July 2012
Diameter: 30-81 µm
Mantle Height: 28-47 µm
Rows of areolae in 10 µm: 12-16


Barrel-shaped frustules are heavily silicified. The valve faces are flat and joined together to form long, filamentous colonies. In girdle view, the mantles are unevenly thickened internally, creating an undulating appearance. A ring of evenly-spaced rimoportulae encircles the mantle, near the valve edge. Several rimoportulae are also present on the surface of the valve. Striae on the valve face are dichotomously branched and radiate from a hyaline central area. Areolae number 13-19 in 10 µm.

Original Description

Basionym: Gallionella undulata
Author: Ehrenb. 1840
Diameter: µm
Rows of areolae in 10 µm:

Original Description

Original Images

Cite This Page:
Bahls, L. (2012). Melosira undulata. In Diatoms of the United States. Retrieved May 26, 2018, from

Species: Melosira undulata

Contributor: Loren Bahls

Reviewer: Sarah Spaulding


Houk, V. (2003). Atlas of Freshwater Centric Diatoms with a Brief Key and Descriptions. Part I. Melosiraceae, Orthoseiraceae, Paraliaceae and Aulacoseiraceae. Czech Phycology Supplement, Volume 1, Czech Phycological Society, Olomouc.

Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.

Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Melosira undulata CAS

North American Diatom Ecological Database (NADED)

NADED ID: 44072

Autecology Discussion

Melosira undulata is reported to be a soil diatom, but is also found in oligotrophic lakes (Krammer & Lange-Bertalot 1991). The population of M. undulata described here was collected on 13 June 2012 at Giant Springs State Park on the Missouri River near Great Falls, Montana. Giant Springs is one of the largest freshwater springs in the world and discharges at a rate of 4.37 cubic meters per second. Water in the springs originates in the Madison limestone formation of the Little Belt Mountains, about 75 miles distant. At the point of discharge, water in the springs measures a constant 12.2 degrees C. The sample containing M. undulata was collected from rocks and concrete that line the spring pool. On the day of collection, water temperature in the pool measured 14.6 degrees C, pH measured 7.50, and specific conductance measured 580 µS/cm. A common diatom associate in this sample was another robust, colony-forming centric: Ellerbeckia arenaria.


A broken frustule of Melosira undulata with intact cytoplasm containing numerous discoid plastids. 400X

Credit/Source: Loren Bahls

Giant Springs on the Missouri River near Great Falls, Cascade County, Montana: home of Melosira undulata.

Credit/Source: Montana Department of Fish, Wildlife & Parks