• Category
  • Length Range
    26.9-59.6 µm
  • Width Range
    9.5-12.3 µm
  • Striae in 10 µm
    13-18 at valve center, 20-24 at the apices

Identification

Description

Valves are lanceolate in smaller specimens to linear-lanceolate with slightly gibbous central margins in the largest specimens. Valve margins are convex and apices are broadly rounded. The raphe is straight and lies between two longitudinal canals. The axial area is narrow and the central area is small and elliptic. Proximal raphe ends are unilaterally deflected. Internally, a rectelevatum is present between the proximal raphe ends; distal raphe ends terminate in helictoglossae. Striae are distinctly curved and strongly radiate throughout. Striae are more distantly spaced in the valve center than in the rest of the valve. Areolae in the central striae appear larger and more distinct than areolae in more distal striae. Under SEM, external areolae openings are complex and highly variable in shape. Terminal raphe fissures are bifurcate and the two branches separate at a very wide angle of almost 180 degrees.

Autecology

Muelleria agnellus has been collected from mossy pools in the alpine zones of the Mission Mountains in Montana and the Wind River Mountains in Wyoming (photos below). These pools lie at elevations of 7,940 feet and 12,319 feet, respectively.

Sample516601 Felsenmeer  Horse Ridge
Credit: Beverly Boynton, Adventurers and Scientists for Conservation.
Mossy pools on Horse Ridge in the Wind River Range, Fremont County, Wyoming: home of Muelleria agnellus.
Sample516601 Samplesite
Credit: Beverly Boynton, Adventurers and Scientists for Conservation.
Closeup of mossy pool on Horse Ridge where Muelleria agnellus was collected.
Missions Sample4 508001
Credit: Bill Agnew, Adventurers and Scientists for Conservation
Mossy pool in the Mission Mountains, Missoula County, Montana: home of Muelleria gibbula.

Original Description

Valves are lanceolate to linear-lanceolate with slightly gibbous central margins in the largest specimens. Valve margins are convex and apices are broadly rounded. Valve length 26.9-59.6 μm; valve width 9.5-12.3 μm. The raphe is straight and filiform between two thickened longitudinal ribs, which occupy a narrow axial area. Proximal raphe ends are bent to the same side within a small elliptic central area. Striae are distinctly curved and strongly radiate throughout. Curved radiate striae meet short parallel striae that border the axial area at an obtuse angle, creating a criss-cross pattern near the valve apices. Areolae in the central striae appear larger and more distinct than areolae in more distal striae. Striae number 13-18 in 10 μm at valve center, 20-24 in 10 μm at the apices.

  • Author
    L.L.Bahls 2014
  • Length Range
    26.9-59.6 µm
  • Width
    9.5-12.3 µm
  • Striae in 10µm
    13-18 at valve center, 20-24 near the apices

Original Images

Figures 98 112

Cite This Page

Bahls, L. (2015). Muelleria agnellus. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/muelleria_agnellus

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Muelleria agnellus 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.