Staurosira stevensonii

Manoylov, E.Morales and Stoermer 2003      Category: Araphid

REPORTED AS: Fragilaria sp. 2 NAWQA EAM (NADED 34179) 

Staurosira construens var. venter


Staurosirella leptostauron

LM scalebar = 10 µm = 80 pixels.


Contributor: Gina LaLiberte - December 2015
Length Range: 18-21 µm
Width Range: 6.9-8.5 µm
Striae in 10 µm: 13.7-19.2


Valves are cruciform and strongly symmetrical. Valves abruptly narrow and extend more than the length of the swollen central area to capitate or subcapitate ends. Striae are alternate and slightly radial at the center to radial at the ends. The axial area is narrow and linear. Marginal spines are present and are particularly visible in girdle view. Spines are longer at the center of cells, resulting in gaps between adjacent cells which are visible in girdle view. Spines are spatulate. Lacks a central area, apical pore field, and rimoportula.

Frustules grow in short chains of a few cells. The colonies may be joined face to face, or joined at only one end of a frustule.

Original Description

Author: Manoylov, E.Morales and Stoermer 2003
Length Range: 18-21 µm
Width Range: 7-9 µm
Striae in 10 µm: 14-19

Original Description

DESCRIPTION: Frustules rectangular in girdle view, often arranged in chains (Figs 5, 6, 11) with the aid of spatulate solid spines (Figs 10, 11). Spines longer at the central area resulting in the separation of the apices of contiguous cells (Figs 5, 11). Valve surface flat (Figs 7, 8, 11). Valves swollen in the central area, elegantly cruciform (Figs 1 - 4, 7, 8), and very symmetrical in valve view (widest in the centre, same as valve width). Ends of the valve rounded or slightly capitate, 1.5 ± 1.8 μm wide. Pseudoraphe distinct with a linear and very narrow central sternum (Figs 1-4, 7, 8). Areolae vary from round along the apical axis to slightly linear along the valve margins, 6 in 1 μm. Striae alternate along the sternum and continue onto the valve mantle (Figs 7 ± 11). Apical pore fields absent or very reduced. Girdle bands open and valvocopulae narrow (Fig. 12). Rimoportulae not present (Figs 9, 11). Chloroplast plate-like and large. Valve length 18 ± 21 μm, width 7 ± 9 μm, and stria density 14 ± 19 per 10 μm.

Original Images

Cite This Page:
LaLiberte, G. (2015). Staurosira stevensonii. In Diatoms of the United States. Retrieved April 23, 2018, from

Species: Staurosira stevensonii

Contributor: Gina LaLiberte

Reviewer: Eduardo A. Morales


Manoylov, K.M., Morales, E.A. and Stoermer, E.F. (2003). Staurosira stevensonii (Bacillariophyta) a new species from Florida, USA. European Journal of Phycology 38: 65-71.

Stoermer, E.F., Andresen, N.A. and Schelske, C.L. (1992). Diatom succession in the recent sediments of Lake Okeechobee, Florida, USA. Diatom Research 7: 367-386. 10.1080/0269249X.1992.9705225

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Staurosira stevensonii CAS

North American Diatom Ecological Database (NADED)

NADED ID: 172014

Autecology Discussion

This taxon was observed in the sediments of Lake Okeechobee, Florida (Stoermer et al. 1992). Frustules are joined in short chains of several cells. In many colonies, adjacent cells are separated near the apices.


Separation between cells as seen in girdle view. Specimens from the holotype population. Academy of Natural Sciences GC 57564

Credit/Source: Gina LaLiberte

Separation between cells as seen in girdle view. Specimens from the holotype population. Academy of Natural Sciences GC57564

Credit/Source: Gina LaLiberte