Eunotia papilioforma

Furey, Johansen and Lowe 2011      Category: Eunotioid

Eunotia panda


Eunotia pectinalis

LM scalebar = 10 µm = 80 pixels.


Contributor: Paula Furey - March 2011
Length Range: 13-35 µm
Width Range: 3.3-4.8 µm
Striae in 10 µm: 13-16


Valves are asymmetric to the apical and transapical axes, with one apex wider than the other. The ventral margin is straight to weakly concave, and the dorsal margin is convex. The apices are rounded, tapered and slightly delimited by a change in the slope of the dorsal margin. These characteristics of the apices, combined with the inset position of the helictoglossa on the ventral margin of each apex, give the apices a ‘nose-like’ appearance. Helictoglossae are set in at different distances from each apex (asymmetry to the transapical axis). One apical rimoportula is present at the wider apex, at the center of that apex. The distal raphe ends curve onto the valve surface. The striae are slightly radiate. Areolae approximately 50 in 10 µm.

Specimens of E. papilioforma are variable in the width of the valve apices and the relative position of the helicotoglossae. Some of this variation is a result of the plane of focus in the microscope; optical dissection is critical to observe valve morphology. Some specimens of E. papilioforma have one more attenuated apex and the helictoglossa is more removed, relative to the opposite end. The shape of the apex with the inset helictoglossa is more characteristic of E. incisa. These valves, however, are dissimilar to the overall E. incisa morphology, which lacks a strong heteropolar variation in apex width and position of the helictoglossae. Specimens of E. papilioforma are similar in morphology to the more asymmetric valves of E. rhomboidea. Eunotia papilioforma, however, is consistently wider than E. rhomboidea (as shown by Camburn et al. 1978; Krammer & Lange-Bertalot 1991). Figures 1-12 (Wuthrich 1975) were classified as E. rhomboidea but are likely more than one taxon. These illustrations show some of the variability discussed here, including variation in the width of the valve apices, position of the helicotoglossae and valve width.

In some specimens of E. rhomboidea, one apex is rounded and the other end is more shaped like the “snout of a shark”. Some specimens possess a small pseudoseptum. The pseudoseptum prevents observation of the base of the rimoportula (in SEM). The rimoportula of E. papilioforma also consistently occurS on the wider end of the valve.

Original Description

Author: Furey, Johansen and Lowe 2011
Length Range: 13-35 µm
Width Range: 3.3- 4.8 µm
Striae in 10 µm: 13-16 , areolae 50

Original Description

Frustules asymmetric to the apical and transapical axes, with one end wider than the other. Valves straight to weakly concave on the ventral margin, convex on dorsal margin, 13 – 35 μm long, 3.3 – 4.8 μm wide. Apices rounded, tapered, slightly delimited by a change in the slope of the dorsal margin, appearing nose-like. Helictoglossae set in from ends, often positioned at different distances from each end, giving appearance of an indentation in the light microscope. Rimoportula at the wider valve end, at the center of the apex. Raphe with distal ends curved onto the valve surface. Striae slightly radiate, 13 – 16 in 10 μm. Puncta 50 in 10 μm.

Original Images

Cite This Page:
Furey, P. (2011). Eunotia papilioforma. In Diatoms of the United States. Retrieved April 19, 2018, from

Species: Eunotia papilioforma

Contributor: Paula Furey

Reviewer: Sam Rushforth


Camburn, K.E., Lowe, R.L., and Stoneburner, D.L. (1978). The haptobenthic diatom flora of Long Branch Creek, South Carolina. Nova Hedwigia 30: 149-279.

Furey, P.C., Lowe, R.L. and Johansen, J.R. (2011). Eunotia Ehrenberg (Bacillariophyta) of the Great Smoky Mountains National Park, USA. Bibliotheca Diatomologica 56: 1-134.

Krammer, K. and Lange-Bertalot, H. (1991). Bacillariophyceae. 3. Teil: Centrales, Fragilariaceae, Eunotiaceae. In Ettl, H., Gerloff, J., Heynig, H. & Mollenhauer, D. (Eds.). Süsswasserflora von Mitteleuropa. 2(3): 1-576. Gustav Fisher Verlag, Stuttgart, Germany.

Wuthrich, M. (1975). Contribution à la connaissance de la flore algologique du Parc National Suisse. Le Diatomées. [Résultats des recherches scientifiques au Parc National suisse]. Druck Lüdin, AG Liestal. Band XIV: 273-369.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

Eunotia papilioforma is widespread on bryophyte substrates in streams throughout the Great Smoky Mountains National Park.


Type locality. Samples collected from bryophytes in Steeltrap Creek, Forney Creek watershed, Swain County, North Carolina, Great Smoky Mountains National Park.

Credit/Source: Paula C. Furey