• Category
  • Length Range
    5.4-23.8 µm
  • Width Range
    2.6-4.4 µm
  • Striae in 10 µm
    19-25 in the middle of raphe valve, 19-28 in the middle of the rapheless valve

Identification

Description

Valves are linear-elliptic, with rounded or slightly protracted apices. The raphe valve is concave with a linear-lanceolate axial area, widening slightly in the middle portion of the valve. Externally, the terminal raphe fissures are hooked toward the same side of the valve. The central raphe ends are teardrop-shaped externally, while internally, they curve to opposite sides of the valve. The rapheless valve is convex with a narrow, linear axial area widening slightly in the middle portion of the valve. Striae are parallel throughout most of both valves, becoming slightly convergent or parallel near apices of the raphe valve and slightly radiate near apices of the rapheless valve. Stria density is 19-25 in 10 µm at valve center and up to 55 in 10 µm near the apices of the rapheless valve. Areolae have small round or slightly transversely elongated external openings and transversely elliptic internal openings occluded by hymenes. Each stria in the middle part of the valve contains 5-6 (occasionally 7) areolae on the valve face and one areola on the mantle.

Autecology

Although formation of mucilaginous stalks was never observed in A. rivulare, this species might be able to produce stalk as other Achnanthidium species.

In the Appalachian region of the US (Ponader and Potapova 2007), A. rivulare was widespread and had a pH optimum of around 7.3, although in previous analysis carried out on the scale of continental US, its pH optimum was around 6 (Potapova and Ponader 2004) . Compared to other species of Achnanthidium in Appalachia, A. rivulare has a greater tolerance for elevated nutrient concentrations. Modeling results indicate that the distribution of this species is related to ionic composition. For example, A. rivulare has an affinity for relatively low calcium and high chloride concentrations.

Original Description

Valves linear-elliptical, 5.4-21.3 µm long, 2.6-4.4 µm wide, with rounded or slightly protracted apices. Raphe valve concave with linear-lanceolate sternum widening slightly only in the middle portion of the valve. Terminal raphe fissures externally hooked toward the same side of the valve. Central raphe endings teardrop-shaped externally, curved to opposite sides internally. Rapheless valve convex, with narrow linear sternum widening slightly in the middle. Striae parallel throughout most of both valves, slightly radiate near apices of rapheless valve and slightly convergent or parallel near apices of raphe valve. Striae density 19-25 in 10 µm at valve center and up to 55 in 10 µm near apices of rapheless valve. Areolae have small round or slightly transversely elongated external openings and transversely elliptical internal openings occluded by hymenes. Each stria in the middle part of the valve contains 5-6 (occasionally 7) areolae on the valve face and one areola on the mantle.

  • Author
    Potapova and Ponader 2004
  • Length Range
    5.4-21.3 µm
  • Width
    2.6-4.4 µm
  • Striae in 10µm
    19-25 in the center raphe valve, 19-28 in the center of the rapheless valve

Original Images

Achnanthidium rivulare orig illus
Achnanthidium rivulare orig descr
Original text and images reproduced with permission by Biopress Ltd..

EMAP Assessment

EMAP Distribution

A Rivulare 10
Map 10

Response Plots

A Rivulare

Cite This Page

Potapova, M. (2009). Achnanthidium rivulare. In Diatoms of North America. Retrieved July 20, 2018, from https://diatoms.org/species/achnanthidium_rivulare

Responses

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