Navicula subrhynchocephala

Hustedt 1935      Category: Symmetrical biraphid
BASIONYM: Navicula subrhynchocephala Hustedt 1935

Navicula subminuscula

 

Navicula subrostellata
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LM scalebar = 10 µm = 80 pixels.

Observations

Contributor: Marina Potapova - March 2011
Length Range: 29-42 µm
Width Range: 7.5-8.9 µm
Striae in 10 µm: 12-14

Description

Valves are linear-lanceolate with variable apices, from subrostrate to capitate. The axial area is narrow and straight. The central area is rounded and slightly asymmetrical. The raphe is straight, with dilated external proximal raphe ends that are hooked towards the secondary side of the valve. The terminal raphe fissures are hooked to the secondary valve side. Striae are radiate, becoming parallel then convergent at the apices. The striae near the center are straight or very slightly bent. The areolae are clearly visible under LM, and number appoximately 24-25 in 10 μm.

Original Description

Basionym: Navicula subrhynchocephala
Author: Hustedt 1935
Length Range: 35-45 µm
Width Range: 6-8 µm
Striae in 10 µm: 13-16

Original Description

Navicula subrhynchocephala nov. spec. Schalen lanzettlich mit vorgezogenen, schwach kopfig gerundeten Enden, 35-45 μ lang, 6-8 μ, breit. Raphe gerade, Endspalten nach gleichen Seiten abgebogen. Axialarea sehr eng, linear, Zentralarea quer elliptisch, ziemlich groß. Transapikalstreifen im mittleren Teil der Schale wenig radial, an den Enden konvergent, 13-16 in 10 μ, zart liniert (Taf. I, Fig. 11) .

Original Images

Cite This Page:
Potapova, M. (2011). Navicula subrhynchocephala . In Diatoms of the United States. Retrieved May 25, 2013, from http://westerndiatoms.colorado.edu/taxa/species/navicula_subrhynchocephala

Species: Navicula subrhynchocephala

Contributor: Marina Potapova

Reviewer: Mark Edlund

Reviewer: Rex Lowe

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Image Credit: Marina Potapova

  1. Valves linear-lanceolate with variable apices
  2. Proximal raphe endings hooked to secondary side
  3. Central striae radiate and straight, or slightly bent
  4. Areolae 24-25 in 10 μm

Valves are linear-lanceolate with subrostrate to capitate apices, 29-42 µm long, 7.5-8.9 µm wide. The central area is rounded and slightly asymmetrical. The raphe is straight, with external proximal raphe ends hooked towards the secondary side of the valve. Striae are radiate, becoming parallel, then convergent at the apices. The central striae are radiate and are straight or very slightly bent. The areolae are clearly visible under LM, approximately 24-25 in 10 μm.

Compare

Navicula subrhynchocephala differs from N. rostellata by straight or very slightly bent central striae, lower areola density and proximal raphe endings hooked to secondary valve side. In N. rostellata, the central striae are bent, the areola density is higher and proximal raphe ends are hooked to the primary valve side.

Navicula rostellata

Citations

Hustedt, F. (1935). Die fossile Diatomeenflora in den Ablagerungen des Tobasees auf Sumatra. "Tropische Binnengewasser, Band VI". Archiv für Hydrobiologie, Supplement 14:143-192.

Lange-Bertalot, H. (2001). Navicula sensu stricto, 10 genera separated from Navicula sensu lato, Frustulia. Diatoms of Europe 2: 1-526.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Navicula subrhynchocephala CAS

North American Diatom Ecological Database (NADED)

NADED ID: 46560

Autecology Discussion

Habits

Size Range

101-1000 µm3 (ie Amphora veneta)

Motility

moderately motile (e.g. Navicula tripunctata)

Attachment

unattached

Habitat

benthic

Colony

solitary

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

Navicula subrhynchocephala

Distribution

The distribution map represents the relative abundance of this Navicula subrhynchocephala 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 Navicula subrhynchocephala was not recorded, or with a red circle indicating the relative abundance of Navicula subrhynchocephala.

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

Navicula subrhynchocephala

Responses

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