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Gomphonema amerhombicum

E.Reichardt 2007      Category: Asymmetrical biraphid

Gomphonema acuminatum


Gomphonema americobtusatum

LM scalebar = 10 µm = 80 pixels.


Contributor: Ian Bishop | Marina Potapova - November 2017
Length Range: 23-60 µm
Width Range: 5.6-7.7 µm
Striae in 10 µm: 13-15 at mid-valve, up to 17 at headpole


Valves are clavate with rounded poles. Raphe is lateral throughout, becoming filiform at proximal ends, where it slightly deflects unilaterally toward an isolated stigmoid. Under SEM multiple isolated puncta are found near the stigmoid at the central area. Axial area is large, mostly rhombic, but expands at mid-valve where it is more circular in shape. Striae are weakly radiate throughout, becoming parallel to convergent at the headpole and increasingly radiate at the foodpool. Stria density increases slightly at headpole. Under SEM, striae are found to be biseriate, composed of two rows of circular to slightly elliptic areolae. Areaolae are not visibly distinct under LM, they are only visible with SEM. A bifurcated apical pore field is present at the footpole. In some specimens, multiple isolated “ghost” puncta are found near the stigmoid at the central area. In girdle view, frustules are rectagular to trapezoidal, and 1-2 rows of pores are present per valve, mostly toward the poles and less so at mid-valve.

This taxon has been confused with the European species, Gomphoneis rhombica (Fricke) Merino, García, Hernández-Mariné and Fernández 1994 (= Gomphonema rhombicum (Fricke) M.Schmidt 1904). Gomphoneis rhombica has dimensions of length as 36-53 µm, width 4.5-7.5 µm and striae of 9.5-12 in 10 µm (Iserentant and Ector 1996). Reports of G. rhombicum from Spain indicate a striae count up to 14 in 10 µm (Reichardt 2007).

Original Description

Author: E.Reichardt 2007
Length Range: 22.0-58.7 µm
Width Range: 5.5-7.6 µm
Striae in 10 µm: 14-16 in the center valve, 16-28 at the ends

Original Description

Frustula aspectu cingulari leviter cuneata serie punctorum distinctorum in prolongatione striarum in partibus distalibus limborum interrupta in media parte.

Valve minime gomphonemoideae-clavatae, lanceolatae verticibus obtuse vel paene late rotundatis plis basalibus angustius rotundatis. Longitudo 22.0-58.7 um, latitudo 5.5-7.6 um (cellulae primae usque ad 8.2 um). Raphe conspicue lateralis fissuris externis paene rectis fissuris internis distincte arcuatis non undulantibus. Extrema interna centralia declinata unilateraliter conspicue curtiora quam extrema externa apparentia. Area axialis modice lata lanceolata in media parte valvarum aream centralem late rhombicam formans. Stigma solitarium unilateraliter in nodulo centrali positum. Striae transapicales radiantes, 14-16 in 10 um sub vertices densiores,, 16-18 in 10 um. Striae seriebus duabus areolarum compositae, puncta in striis non aspectabilia in microscopio photonico.

Original Images

Cite This Page:
Bishop, I., and Potapova, M. (2017). Gomphonema amerhombicum. In Diatoms of the United States. Retrieved May 25, 2018, from

Species: Gomphonema amerhombicum

Contributor: Ian Bishop | Marina Potapova

Reviewer: Rosalina Stancheva


Ector, L., Coste, M. and Iserentant, R. (1995). Taxonomie et ultrastructure de Gomphonema rhombicum Fricke, 1904. Comparaison avec Gomphonema clevei Fricke, 1902 et Gomphonema brevistriata Héribaud, 1903. Vie et Milieu 45: 339.

Iserentant, R. and Ector, L. (1996). Gomphonema rhombicum M. Schmidt (Bacillariophyta): typification et description en microscopie optique. Bull. Ft. Peche Piscic 341/342: 115-124.

Ponader, K.C., Potapova, M.G., Desianti, N., Hamilton, P.B., Lavoie, I., and Campeau, S. (2017). Gomphonema caperatum sp. nov., G. obstipum sp. nov. and similar taxa from rivers of North America. Diatom Research 32 (1): 59-73.

Reichardt, E. (2007). Neue und wenig bekannte Gomphonema-Arten (Bacillariophyceae) mit Areolen in Doppelreihen. Nova Hedwigia 85: 102-137. 10.1127/0029-5035/2007/0085-0103

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Gomphonema amerhombicum CAS

North American Diatom Ecological Database (NADED)


Autecology Discussion

Gomphonema amerhombicum appears to be common across the western United States. The type population is from Oak Creek, Arizona. Several more populations have been examined (see below). This taxon is relatively common in rivers, as sampled by the US Geological Survey National Water Quality Assessment (NAWQA) program from California, Washington and Oregon. The species was original described from New Mexico (Reichardt 2007).


Two distinct Gomphonema amerhombicum populations from two samples collected in the Sierra Nevada Mountains in California. Scale bars = 10 um.

Credit/Source: Ian Bishop

Two distinct Gomphonema amerhombicum populations from two samples collected in the Willamette Valley in Oregon. Scale bars = 10 um.

Credit/Source: Ian Bishop

Two distinct Gomphonema amerhombicum populations from two samples collected in the Puget Sound Basin in Washington. Scale bars = 10 um.

Credit/Source: Ian Bishop