• Category
  • Length Range
    35.0-53.9 µm
  • Width Range
    6.5-7.5 µm
  • Striae in 10 µm
    12.1-14.5 at valve center, 14.2-16.2 at headpole, 11.7-15.4 at footpole

Identification

Description

Valves are clavate-lanceolate, broadest at the central area, which is positioned slightly toward the headpole. Valve ends are unprotracted. The headpole end of the valve has convex margins. The headpole is rounded, more acutely in smaller specimens. The footpole end of the valve has straight margins, which narrow to an acutely rounded footpole. A small pseudoseptum is evident at the footpole. The valve face-mantle junction appears to be rounded. The axial area is lanceolate, about 1/3 breadth midway toward the valve ends, expanded to a broader apically elliptic central area that is bounded by short, evenly spaced striae. A single stigmoid is located in an oval depression in the central area, distant from and unassociated with the striae, positioned close to the proximal raphe ends. Raphe is filiform and straight. The headpole raphe terminus initially deflected toward stigmoid side of valve before returning to a medial position. Proximal raphe ends are closely spaced, proximal ends are sharply reflexed toward the stigmoid in deep focus. At the valve center, striae are subparallel. Toward the footpole, striae become slightly radiate.Toward the headpole, striae become slightly radiate before becoming subparallel to slightly convergent. Areolae are relatively coarse, apically elongate, usually discernible in LM, 25.6-32.8 in 10 µm. A large apical pore field split by raphe end is evident at the footpole.

There are several problems with determining the identity of this taxon. In the original description (Lowe & Kociolek 1984, p 472, Figs 21-22): 1) no scale bar is provided on the illustrated specimens; 2) the illustrated specimens do not correspond to the holotype specimen that is circled on ANSP GC-53921; 3) the circled type specimen (identified above) does not closely correspond to the description (circled type is only 37 µm long); 4) the population of specimens on the type slide differs from the original description by having smaller size (35-54 µm rather than 45-70 µm) and higher stria density (12-1-14.5 in 10 µm rather than 10-11 in 10 µm). Because ANSP GC-53921 is clearly designated as the type we must defer to the circled type specimen and use the range of taxa on the type slide as a starting point to define this taxon. Other reports of this taxon (e.g., Thomas & Kociolek 2009, Figs 106-108) appear to more closely follow the illustrated specimens in Lowe & Kociolek (1984) rather than the type material.

Autecology

This species was originally described from the Abrams Creek watershed (Great Smoky Mountains National Park, Tennessee) as an epiphyte on the aquatic moss Fontinalis.

Original Description

Valve linear, being only slightly tumid and the valve center. Valves 45-75 µm long, 7-8 µm wide. Axial area small at the ends, becoming expanded towards mid-valve. Central area more heavily silicified than the rest of the valve, possessing an isolate punctum. Striae parallel throughout, 10-11 in 10 µm. Raphe filamentous.

  • Author
    R.L.Lowe and Kociolek 1984
  • Length Range
    45-75 µm
  • Width
    7-8 µm
  • Striae in 10µm
    10-11

Original Images

Lowe Et  Koceiolk1984  Gomph Freesei
Gomph Freesei Type Slide  Gc53921
Lowe   Kociolek 1984 Orig Descrip  Gomph Freesei

Cite This Page

Edlund, M, and Lee, S. (2016). Gomphonema freesei. In Diatoms of North America. Retrieved July 22, 2018, from https://diatoms.org/species/gomphonema_freesei

Responses

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