Diatoms of North AmericaDiatoms of North America

Gomphonema apuncto

J.H.Wallace 1960

Gomphonema Apuncto Guide
  • Category
    Asymmetric Biraphid
  • Length Range
    21.0-30.7 µm
  • Width Range
    3.0-4.1 µm
  • Striae in 10 µm
    13-16

Identification

Gomphonema apuncto LM4 Gomphonema apuncto LM1 Gomphonema apuncto LM3 Gomphonema apuncto LM2 Gomphonema apuncto LM5
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Description

Valves are nearly linear, with a rounded headpole and narrowly rounded footpole. The axial area is lanceolate and relatively broad. A stigmoid is absent. The raphe is lateral and straight. The external proximal raphe ends are expanded and are placed close to one another. The external distal raphe ends are deflected in the same direction. The internal proximal raphe ends are sharply recurved and distinct. The central nodule is thickened and distinct. Striae are radiate, becoming nearly parallel at the headpole and more strongly radiate at the footpole.

The specimens shown here are from the type slide. Gomphonema apuncto appears to be a rare taxon, restricted to rivers of the southeast states. Many of the records of G. apuncto appear to be misidentifications. This taxon may be confused with small valves of G. christenseni and perhaps other, as yet undescribed, species.

Autecology

Gomphonema apuncto appears to be a rare taxon in rivers, restricted to the southeast states. In the original description (Wallace 1960), it was described from the Flint River, Georgia. That publication also reported it from the North Fork of the Holston River, Smyth County, Virginia.

Original Description

Gomphonema apuncto nov. sp.

Valvis angustis, sublinearibus, medio paullo tumidis, apicubus obtusis, 15-28, μ longis, 4-4.5 μ latis, striis abbreviatis, marginalibus, 13-15 in 10 μ, radiantibus.

This species is very similar to Gomphonema tenuissimum Fricke, A. Schmidt's Atlas, pl. 248, fig. 7, 1904, except that G. tennuissimum has a punctum or stigma, which is lacking in this species. Since the absence or presence of this stigma is the character on which Grunow founded his subgenera, it seems more feasible to make this a new species rather than a variety of Fricke's species.

In the collection from which the type slide was made, this species occurred as an almost complete dominant. In other collections from the same station where it occurred with less frequency, Anomoeoneis exilis (Kütz.) Cl. and Achnanthes minutissima Kütz. were the dominants. It also occurred in the North Fork of the Holston River, Smyth County, Virginia.

Type.--Flint River, Worth County, Georgia, Coll. R. Patrick, September, 1952

  • Author
    J.H.Wallace 1960
  • Length Range
    15-28 µm
  • Width
    4-45 µm
  • Striae in 10µm
    13-15

Original Images

Gomphonema apuncto orig illus
G Apunctoorigdesc

Citations & Links

Citations

Links

Cite This Page

Polaskey, M., Vaccarino, M. (2016). Gomphonema apuncto. In Diatoms of North America. Retrieved December 03, 2024, from https://diatoms.org/species/gomphonema_apuncto

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Gomphonema apuncto 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.