• Category
  • Length Range
    16-50 µm
  • Width Range
    4.1-7.9 µm
  • Striae in 10 µm
    9-13 at dorsal center; 15-18 at dorsal apices; 19-20 ventral
  • Reported As
    Amphora acutiuscula (Patrick and Reimer 1975, pg. 77, Pl. 14, Figs. 9-10)
    Halamphora acutiuscula (ANSP Image Database (IM000479, IM002259, IM002260))



Valves are semi-elliptical, 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 are not visible in LM.

Patrick and Reimer (1975) used the name Amphora acutiuscula in their volume, Diatoms of the United States, for a taxon conspecific with the specimens shown on this page. Like these illustrated specimens, the Patrick and Reimer material was also collected from the Sabine River, Texas. Patrick and Reimer did not, however, examine Kützing's original material. Kützing's type material was revisited by Levkov (2009, Pl. 265), but the type of Amphora acutiuscula varies considerably from the Patrick and Reimer concept. The species Halamphora latecostata described by Stepanek and Kociolek (2013) conforms to the taxon illustrated here, and also to the taxon to which Patrick and Reimer misapplied the name A. acutiuscula.

While Levkov (2009) imaged Kützing's type material (Pl. 265, Figs. 12-15), he did not refer to this plate in his recombination of Halamphora acutiuscula, but instead referred to a Venezuelan population (Pls. 96, 109, 234) dissimilar to Kützing's type. The comparison of H. latecostata to H. acutiuscula found on this page refers to the type images only (Pl. 265).


The specimens shown on this page were collected by Ruth Patrick in 1952, from the epipsammon of the Sabine River, Texas.

Original Description

  • Author
    Štěpánek and Kociolek 2013
  • Length Range
    25-40 µm
  • Width
    5.5-7.5 µm
  • Striae in 10µm
    10 in the center (dorsal), 14-15 at the apices (dorsal), 18-22 on the ventral side

Original Images

Hal Latecostata Orig Desc Plate
Hal Latecostata Orig Desc Text


Dec 11, 2015 - Correction to identification

This page was originally posted as Halamphora acutiuscula sensu Patrick and Reimer 1975. After this page was opened, however, the contributor became aware that this taxon conforms to H. latecostata Stepanek and Kociolek (2013). The name was changed as of the current date from Halamphora acutiuscula to Halamphora latecostata. - I. Bishop and S. Spaulding

Cite This Page

Bishop, I. (2015). Halamphora latecostata. In Diatoms of North America. Retrieved August 19, 2018, from https://diatoms.org/species/halamphora_latecostata


The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Halamphora latecostata from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.