Aulacoseira muzzanensis

(F.Meister) Krammer 1991      Category: Centric
BASIONYM: Melosira muzzanensis F.Meister 1912
SYNONYM(S): Aulacoseira granulata var. muzzanensis (F.Meister) Simonsen  

Aulacoseira lirata


Aulacoseira nivalis

LM scalebar = 10 µm = 40 pixels.


Contributor: Marina Potapova | Jonathan English - February 2011
Diameter: 9-24 µm
Mantle Height: 5-13 µm
Rows of areolae in 10 µm: 7-15


Frustules are cylindrical and form colonies that often consist of separation cells only. Linking valves are rare. Valves are 9-24 µm in diameter, with a mantle height of 5-13 µm. The ratio of the mantle height to valve diameter is 0.4-1.2. The mantle has straight sides and the valve face is flat or vary slightly convex or concave. The rows of areolae are almost straight and parallel to pervalvar axis in separation valves, but often curved to the right in linking valves, 7-15 in 10 µm. The mantle areolae are square, but often appear oval in LM. Areolae in some valves are coarse and disorganized. The straight rows of areolae often appear as biseriate in LM. The valve face has small scattered areolae. Linking spines are located at the end of each pervalvar costa. They are short, triangular or bifurcated. Separation spines originate from two pervalvar costae. Most separation spines are 0.5-2 µm long, but some spines are longer, and 1 -2 are almost equal in length to the valve mantle. These long spines have corresponding grooves on the mantle of sibling valves. The ringleiste is solid and moderately shallow. At least one coiled rimoportula is positioned on the mantle at the distance of 1-3 areolae from the collum, usually in the groove, and another one is positioned close to the valve face.

The structure of the frustule is essentially the same as in A. granulata with all characters overlapping between two species. Until further studies clarify the taxonomy of this species complex, we recommend differentiating these two species using an arbitrary rule: if the ratio of the mantle height to valve diameter in at least some cells in a colony is less than 0.8, or if it is between 0.8 and 1.2, but areolae are coarse and disorganized, a specimen is identified as A. muzzanensis. If this ratio in all cells is greater than 0.8, or it is between 0.8 and 1.2, but areolae are organized in regular rows, it is identified as A. granulata.

Note that Krammer (1991) provided LM and SEM images of the syntype slide from the Lago di Muzzano, Ticino (mounted by Meister 16.9.1906, coll Hustedt slide A1/50). These images include specimens that are similar to the original Meister illustration (shown below), as well as specimens that conform to North American specimens.

Original Description

Basionym: Melosira muzzanensis
Author: F.Meister 1912
Diameter: 12-14 µm
Mantle Height: 6-8 µm
Rows of areolae in 10 µm: 11-13

Original Description

Valvis circularibus, planis, laevibus, margine striolato, striis ab-breviatis; diametro disci 12—14 μ; latere connectivali late rectangu-lari, 15—24 μ alto; polis subrotundatis cum spinulis brevissimis, vix visibilibus; tunica 6—8 μ alta, punctata; punctis secus lineas 11—13 in 10 μ obliquas ordinatis; margine commissurali angusto, sulcis paulo exaratis; frustulis in filamenta elongata, recta conjunctis.

Original Images

Cite This Page:
Potapova, M., and English, J. (2011). Aulacoseira muzzanensis. In Diatoms of the United States. Retrieved April 20, 2018, from

Species: Aulacoseira muzzanensis

Contributor: Marina Potapova | Jonathan English

Reviewer: Sarah Spaulding


Krammer, K. (1991). Morphology and taxonomy in some taxa of the genus Aulacoseira Thwaites (Bacillariophyceae). II. Taxa in the A. granulata-. italica- and lirata-groups. Nova Hedwigia 53: 477-496.

Meister, F. (1912). Die Kieselalgen der Schweiz. Beiträge zur Kryptogamenflora der Schweiz, 4/1, 1–254.

Stoermer, E.F. and Andresen, N.A. (1990). Aulacoseira agassizii in North America. Nova Hedwigia, Beiheft 100: 217-223.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Aulacoseira muzzanensis CAS

North American Diatom Ecological Database (NADED)

NADED ID: 10031

Autecology Discussion

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

Aulacoseira muzzanensis

EMAP Response Plots

Aulacoseira muzzanensis

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.