Halamphora acutiuscula

Kützing 1844      Category: Asymmetrical biraphid
BASIONYM: Amphora acutiuscula Kützing 1844
SYNONYM(S): Amphora coffeaeformis var. acutiuscula (Kützing) Hustedt 1930 | Amphora coffeaeformis var. acutiuscula (Kützing) Rabenhorst 1864 

Gyrosigma attenuatum


Halamphora coffeaeformis

LM scalebar = 10 µm = 80 pixels.


Contributor: Ian Bishop - November 2015
Length Range: 16-50 µm
Width Range: 4.1-7.9 µm
Striae in 10 µm: 9-13 in the middle (dorsal); 15-18 at the apices (dorsal); 19-20 on the ventral side


Valves are semi-lanceolate, with rounded dorsal margins and nearly straight ventral margins that vary from slightly concave to slightly convex. Apices are distinctly protracted, round and subcapitate to capitate. Dorsal striae are radiate throughout, increasing from 9-13 in 10 µm near the center to 15-18 in 10 µm at the apices. Ventral striae are shortened and radiate to parallel. The ventral striae are interrupted at the center and vary little from 19-20 in 10 µm across the valve. The axial area is linear. On the dorsal side, the axial area is narrow. On the ventral side, the axial area expands near the central area. The raphe is filiform. The proximal raphe ends are inflated and deflect slightly to the dorsal side of the valve. Areolae not visible in LM.

The morphology and size range presented here conforms to the concept presented in Patrick and Reimer (1975).

In contrast, a population from Germany imaged in Levkov (2009, Figs 96: 10-18) differs from the concept of Patrick and Reimer. Specifically, those specimens have a wider ventral area with no striae interruption, visibly punctate dorsal striae, and a silicious internal thickening in the dorsal central area. This last feature is noted by Patrick and Reimer as belonging to Halamphora sabiniana, a closely related species.

The original type material of Kützing will need to be examined resolve the identity of H. acutiscula.

Original Description

Basionym: Amphora acutiuscula
Author: Kützing 1844
Length Range: µm
Striae in 10 µm:

Original Description

AMPHORA ACUTIUSCULA. Taf. 5. Fig. XXXII. (420/1). A. lanceolata, apicibus acuminatis acutiusculis l. obtusiusculis, striis, longitudinalibus marginalibus validis. - Long. 1/48”. Im Busen von Genua!

Original Images

Cite This Page:
Bishop, I. (2015). Halamphora acutiuscula. In Diatoms of the United States. Retrieved November 29, 2015, from http://westerndiatoms.colorado.edu/taxa/species/halamphora_acutiuscula

Species: Halamphora acutiuscula

Contributor: Ian Bishop

Reviewer: Rex Lowe


Kützing, F.T. (1844). Die kieselschaligen Bacillarien oder Diatomeen. Nordhausen. 152 pp., 30 pls.

Levkov, Z. (2009). Amphora sensu lato. In Diatoms of Europe, Volume 5. (H. Lange-Bertalot, ed). A.R.G. Gantner Verlag K.G. 916pp.

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Links & ID's

Index Nominum Algarum (INA)

Original INA
Transfer INA

California Academy of Sciences (CAS)

Halamphora acutiuscula CAS

North American Diatom Ecological Database (NADED)

NADED ID: 9098002

Autecology Discussion

The specimens shown on this page were collected from an epipsammic sample of the Sabine River, Texas.