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Melosira normannii

S.Arn. ex Van Heurck 1882      Category: Centric

REPORTED AS: Cyclotella fottii (Reavie and Smol 1998) | Melosira undulata var. normannii (Stoermer 1980) 

Melosira dickiei


Melosira undulata

LM scalebar = 10 µm = 20 pixels.


Contributor: Mark Edlund | David R.L. Burge - July 2017
Diameter: 33.9-62.9 µm
Mantle Height: 13.5-21.7 µm
Rows of areolae in 10 µm:


Cells are large, heavily-silicified and arranged in short filaments of 2-15 cells. The mantle height is variable, with larger cells having comparably shorter mantles. The valve face is flat to slightly convex and meets the mantle at a right angle. The valve face has a small central area, with scattered areolae. The central area is surrounded by spirally arranged and anastamosing rows of coarse areolae (areolae number 14-21 in 10 µm). Striae continue onto the valve mantle, where they are arranged in straight pervalvar rows (14.5-16.7 striae in 10 µm) with a areolae density similar to that on the valve face. The mantle has multiple, large rimoportulae which are located closer to the valve face than to the mantle margin. The rimportulae are regularly spaced. In valve view, deep focus on the inner outline of the mantle shows a characteristic polygonal outline. In girdle view, deep focus shows a thick, bullulate cell wall structure.

Original Description

Author: S.Arn. ex Van Heurck 1882
Diameter: µm
Rows of areolae in 10 µm:

Original Description

Original Images

Cite This Page:
Edlund, M., and Burge, D. (2017). Melosira normannii. In Diatoms of the United States. Retrieved May 25, 2018, from

Species: Melosira normannii

Contributor: Mark Edlund | David R.L. Burge

Reviewer: Sarah Spaulding


Reavie, E.D. and Smol, J.P. (1998). Freshwater diatoms from the St. Lawrence River. Bibliotheca Diatomologica Band 41. J. Cramer, Berlin. 137 pp.

Stoermer, E.F. (1980). Characteristics of benthic algal communities in the upper Great Lakes. U.S. Environmental Protection Agency, Ecological Research Series, EPA 600/3-80-073. Environmental Research Laboratory, Duluth, Minnesota. 72 pp.

Stoermer, E. F. and Yang, J. J. (1969). Plankton diatom assemblages in Lake Michigan. Univ. Michigan, Great Lakes Res. Div. Spec. Rep. No. 47, 168 pp.

Van Heurck, H. (1882). Synopsis des Diatomées de Belgique, Atlas. Anvers: Ducaju et Cie. Plates LXXVIII-CIII.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Melosira normannii CAS

North American Diatom Ecological Database (NADED)

NADED ID: 44062

Autecology Discussion

Melosira normannii is not regularly encountered in collections. It prefers oligo- to mesotrophic waters and seems to be more common in more northerly regions. It is a benthic diatom and seems to prefer deep, sandy or fine-grained sediments. Material illustrated here comes from northern Minnesota boreal lakes, a lake in Isle Royale National Park, and from epipsammon on the St. Croix River, Minnesota-Wisconsin. Below are living cells of Melosira undulata var. normannii showing how their short filaments produces large mucilage strands that hold cells among sand grains (St. Croix River, MN). Stoermer (1980) illustrates specimens from Lake Michigan and Lake Superior and notes that it is found in regions that are isolated from direct pollution sources and that its primary habitat is epipelon. Stoermer and Yang (1969) report in Lake Michigan that it is rare in the plankton, can be found as deepwater periphyton, and that the “var. normannii” is more northern than the nominate varety. Reavie and Smol (1998) found it rare in sediment cores from the St. Lawrence River and that it was not observed in modern material.


Live Melosira normannii with prominent mucilage stalks binding sand grains together in the St. Croix River, Minnesota.

Credit/Source: Mark Edlund

Girdle view showing pervalvar rows of areolae and ring of rimoportula. Collected from Jasper Lake drain, BWCAW, Cook County, Minnesota.

Credit/Source: Mark Edlund