Rossithidium pusillum

(Grunow) Round et Bukhtiyarova 1996      Category: Monoraphid
BASIONYM: Achnanthes pusilla Grunow 1880
SYNONYM(S): Achnanthes pusilla Grunow in Cleve & Grunow 

Rossithidium petersenii

 

Sellaphora bacilloides
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LM scalebar = 10 µm = 80 pixels.

Observations

Contributor: Marina Potapova - May 2009
Length Range: 10–16 µm
Width Range: 3.1-4.1 µm
Striae in 10 µm: 20-24

Description

Valves linear or linear-elliptical with rounded ends, 3.1-4.1 µm wide, 10-16 µm long. Raphe valve with narrow axial area and with small round or irregular central area. Terminal raphe fissures absent. Raphe straight, filiform. Central raphe endings curved to opposite sides internally. Rapheless valve with narrow linear axial area without a central area or with a very small asymmetrical central area. Striae uniseriate, slightly radiate, one or two striae in the middle portion of the raphe valve are thicker than the rest, 20-24 in 10 µm. External openings of areolae are isodiametric or slightly elongated transapically. Each stria in the middle part of the valve contains 4-5 areolae. The valve mantle bears one row of areolae.

Original Description

Basionym: Achnanthes pusilla
Author: Grunow 1880
Length Range: 13-17 µm
Width Range: 3–4 µm
Striae in 10 µm: 18-23 in 10 µm

Original Description

Schaalen linear mit abgerundeten Enden. Querstreifen der Overschaale fast parallel, der Unterschaale schwach radial, die mittelsten entfernter und starker, 18-23 in 0.01 mm. Schaalen 0,013-0,017 mm. lang, 0.003-0,004 mm breit. Finshoe, Norwegen. Nordstedt.

Original Images

Cite This Page:
Potapova, M. (2009). Rossithidium pusillum. In Diatoms of the United States. Retrieved May 23, 2013, from http://westerndiatoms.colorado.edu/taxa/species/Rossithidium_pusillum

Species: Rossithidium pusillum

Contributor: Marina Potapova

Reviewer: Sarah Spaulding

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Image Credit: Marina Potapova

  1. Valve linear to linear-elliptical
  2. Raphe straight, without distinct terminal raphe fissures
  3. Striae unseriate, slightly radiate throughout both valves
  4. One or two striae in the center of the raphe valve more broad than the other striae

Valves are linear to linear-elliptical or linear-lanceolate with rounded ends. The terminal raphe fissures are not distinct. The striae are uniseriate, with 4-5 areolae per stria, and slightly radiate throughout both valves.

Compare

Rossithidium pusillum is similar to A. rivulare in valve shape, but the terminal raphe fissures of R. pusillum are not distinct. Achnanthidium minutissimum valves are more linear or linear-elliptical in shape. Rossithidium nodosum has coarser striae but lacks the two irregularly broad striae in the center of the raphe valve.

Achnanthidium rivulare

Achnanthidium minutissimum

Rossithidium nodosum

Citations

Cleve, P.T. and Grunow, A. (1880). Beiträge zur Kenntniss der Arctischen Diatomeen. Kongliga Svenska-Vetenskaps Akademiens Handlingar, Vol: 17, Issue: 2, 121 pp., 7 pls.

Round, F. E. and Bukhtiyarova, L. (1996). Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11: 345-361.

Links & ID's

Index Nominum Algarum (INA)

Transfer INA
Original INA

California Academy of Sciences (CAS)

Rossithidium pusillum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 189003

Autecology Discussion

As other monoraphid diatoms, Rossithidium pusillum is only slightly motile. Coldwater, oligotraphentic species.

Habits

Size Range

11-100 µm3 (ie Achnanthidium)

Motility

slightly motile (e.g. Cocconeis)

Attachment

prostrate (e.g. mucilage pad)

Habitat

benthic

Colony

EMAP Assessment

Sampling for 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). Streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming). Over 1200 sites on 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

Rossithidium pusillum

Distribution

The distribution map represents the relative abundance of this Rossithidium pusillum in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Rossithidium pusillum was not recorded, or with a red circle indicating the relative abundance of Rossithidium pusillum.

Note that the size of the proportional symbols varies between species to help show both abundant and rare species.

Scale for the map to the left

EMAP Response Plots

Rossithidium pusillum

Responses

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

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.