• Category
  • Diameter
    9-24 µm
  • Width Range
    5-13 µm
  • Striae in 10 µm
  • Synonyms
    Aulacoseira granulata var. muzzanensis (F.Meister) Simonsen



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

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.

  • Basionym
    Melosira muzzanensis
  • Author
    F.Meister 1912
  • Length Range
    12-14 µm
  • Width
    6-8 µm
  • Striae in 10µm

Original Images

Melosira muzzanensis orig illus
Melosira muzzanensis orig illus

Cite This Page

Potapova, M., English, J. (2011). Aulacoseira muzzanensis. In Diatoms of North America. Retrieved July 15, 2024, from https://diatoms.org/species/aulacoseira_muzzanensis


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Aulacoseira muzzanensis from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.