Aulacoseira italica

(Ehrenb.) Simonsen  1979      Category: Centric
BASIONYM: Gaillonella italica Ehrenb. 1838
SYNONYM(S): Melosira italica  (Ehrenb.) Kütz. 
REPORTED AS: Aulacoseira crenulata (Thwaites 1848) 

Aulacoseira islandica


Aulacoseira lirata

LM scalebar = 10 µm = 40 pixels.


Contributor: Marina Potapova | Jonathan English | Mark Edlund - December 2010
Diameter: 4-24 µm
Mantle Height: 9-20 µm
Rows of areolae in 10 µm: 17-25


Frustules are cylindrical and are connected face-to-face to form filamentous colonies. Valves are 4-24 µm in diameter, with a mantle height of 9-20 µm. The ratio of the mantle height to valve diameter usually ranges from 0.7 to 5. The mantle has almost straight sides, and the valve face is flat with slightly convex margins. The straight or slightly sinuous rows of mantle areolae are inclined to the left (sinistrorse) or almost parallel to the pervalvar axis, 17-25 rows in 10 µm. The mantle areolae vary in shape from circular to slit-like. Spines are large, spatulate or anvil-shaped and originate from two to four costae. One or more pervalvar rows of areolae terminate at the base of the spine. Separation valves are rare and have thinner, pointed spines than linking valves. The number of rimoportulae is most often two, but may be one or more per valve. Externally, the rimoportula openings are not distinguishable from areolae. The ringleiste is solid, shallow, and thick. Resting spores are often observed and produced as semi-endogenous pairs. Spore frustules superficially resemble those of vegetative cells, but conspicuously lack visible spines, have thicker cell walls, may have a convex valve face, and often have incomplete rows of mantle areolae. Not all populations of A. italica appear to form resting spores; spores are especially common in fossil deposits and in populations from shallow polymictic lakes.

There has long been confusion surrounding the identity of Aulacoseira italica. Crawford et al. (2003) studied type material of both A. italica (Gallionella italica) and A. crenulata, confirmed that they represented the same taxon, and that A. italica was the earlier and correct name. Note that in the type material, the rimoportulae (illustrated in Crawford et al. 2003) are positioned along a stria about 4-5 areolae from the ringleiste and appear internally as long, straight tubes integral with the valve wall. In material from Florida, rimoportulae appear internally as short, sessile processes. The spore forms have also been separately named as Melosira laevis and M. semilaevis (Van Heurck 1882)

Original Description

Basionym: Gaillonella italica
Author: Ehrenb. 1838
Diameter: 6 µm
Rows of areolae in 10 µm:

Original Description

Sie unterscheidet sich durch einen gekerbten Cirkelrand von G. distans, könnte aber, da ich nur wenige, nicht völlif deutliche, Exemplare sah, zum Jugendzustand der G. varians gehören. – Grösse 1/384 Linie.

Original Images

Cite This Page:
Potapova, M., English, J., and Edlund, M. (2010). Aulacoseira italica. In Diatoms of the United States. Retrieved April 26, 2018, from

Species: Aulacoseira italica

Contributor: Marina Potapova | Jonathan English | Mark Edlund

Reviewer: Sarah Spaulding


Crawford, R.M., Likhoshway, Y.V. and Jahn, R. (2003). Morphology and identity of Aulacoseira italica and typification of Aulacoseira (Bacillariophyta). Diatom Research 18: 1-19. 10.1080/0269249X.2003.9705569

Ehrenberg, C.G. (1838). Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben de Natur. erlag von Leopold Voss, Leipzig. pp. 1-xvii, 1-548, pls. 1-64.

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

Simonsen, R. (1979). The diatom system: ideas on phylogeny. Bacillaria 2: 9-71.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Aulacoseira italica CAS

North American Diatom Ecological Database (NADED)

NADED ID: 10019

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 italica

EMAP Response Plots

Aulacoseira italica

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.