Pseudostaurosira parasitica

(W.Sm.) E.Morales      Category: Araphid
BASIONYM: Odontidium parasiticum W.Sm. 1856
SYNONYM(S): Fragilaria parasitica (W.Sm.) Grunow in Van Heurck | Synedra parasitica (W.Sm.) Hust. | Synedrella parasitica (W.Sm.) Round in Maidana 

Pseudostaurosira neoelliptica


Pseudostaurosira pseudoconstruens

LM scalebar = 10 µm = 80 pixels.


Contributor: Eduardo A. Morales - October 2010
Length Range: 9-18 µm
Width Range: 4.5-5 µm
Striae in 10 µm: 19-21


Valves are lanceolate, 4.5-5 µm wide by 9-18 µm long. Valves with subrostrate to subcapitate ends in larger specimens, cuneate in smaller specimens. Valve face flat or slightly undulate due to raised costae. The valve face/mantle junction forms a sharp angle. In girdle view, frustules are rectangular, solitary and often attached to other diatoms by a mucilage stalk. The axial area is widely lanceolate. Striae are distinct, composed of wide, round to oval areolae, 19-21 in 10 µm. Striae vary from parallel to radiate in the central area to slightly radiate toward the valve ends and extend onto the valve mantle. The costae are broad. Spines are absent. Well-developed apical pore fields with round poroids are present on the transition between valve face/mantle and are recessed into the valve ends.

Specimens from samples in the US sites show at least two morphological variants, often mixed in material from a single locality. One variant has slender, protracted and rostrate ends, while the other has wider more subcapitate ends.

Original Description

Basionym: Odontidium parasiticum
Author: W.Sm. 1856
Length Range: µm
Striae in 10 µm:

Original Description

Frustules rarely cohering, attached by their extremities; valves direct, elliptical, and acute. Length of frustule .0005” to .0009”. v.v

Original Images

Cite This Page:
Morales, E. (2010). Pseudostaurosira parasitica. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Pseudostaurosira parasitica

Contributor: Eduardo A. Morales

Reviewer: Sarah Spaulding


Morales, E.A. (2003). On the taxonomic position of the Belonastrum and Synedrella, two new fragilarioid genera described by Round and Maidana (2001). Cryptogamie Algologie 24: 277-288.

Round, F.E. and Maidana, N.I. (2001). Two problematic freshwater araphid taxa re-classified in new genera. Diatom. The Japanese Journal of Diatomology 17: 21-28.

Smith, W. (1856). Synopsis of British Diatomaceae. John Van Voorst, London 1856. 2: 107pp., pls. 32-60, 61-62, A-E.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Pseudostaurosira parasitica CAS

North American Diatom Ecological Database (NADED)

NADED ID: 73010

Autecology Discussion

EMAP Assessment

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). Over 1200 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

Pseudostaurosira parasitica

EMAP Response Plots

Pseudostaurosira parasitica

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.