• Category
  • Length Range
    18.8-25.1 µm
  • Width Range
    5.5-5.9 µm
  • Striae in 10 µm
    14-16 at midvalve; 19-21 toward the apices

Identification

Description

Valves are linear to linear-lanceolate, with protracted, rostrate to sub-capitate, broadly rounded apices. Striae are radiate and curved, becoming nearly parallel at the apices. Striae are considerably less dense at mid-valve, and striae here are occasionally shortened. Areolae are dense and difficult to visualize under LM, except along the axial area at mid-valve, where individual areolae are less dense and can be discriminated. The axial area is very narrow and expands slight to a small, round central area. The raphe is straight with inflated proximal ends.

The specimens shown above conform to the type illustration and dimensions of Navicula genovefae Fusey 1951. Unfortunately, however, we were unable to obtain Fusey material (it was either lost or destroyed).

This taxon should be compared to Prestauroneis protractoides (Hust.) Liu and Kociolek 2015, as the two taxa have been confused in surveys in North America. The identity of this taxon, however, is also problematic to resolve. The lectotype specimen of N. protractoides Hust. is difficult to reconcile with the type illustration. Hustedt mentions an expanded mid valve ("Schalen linear in der Mitte konvexen Rändern” OR "medio convexis”) that is not present in the lectotype specimen. It appears that the illustration is not representative of the specimen, or the specimen selected as the lectotype is not of the taxon Hustedt intended. Alternatively, one could argue that there are two similar taxa on the Hustedt slide; resolution requires further work.

Note that a Parlibellus protractoides (Hust.) Witkowski and Lange-Bertalot 2000 is a homotypic synonym of P. protractoides.

Autecology

To date, this taxon has only been reported from California, Oregon and Washington. It may have a broader distribution, as it has been reported also as Prestauroneis protractoides (Hust.) Liu and Kociolek 2015.

In Oregon, it was found in Fanno Creek, a nearly completely urban, and highly impacted watershed of the Portland metropolitan area.

Fanno  Creek  Durham  Oregon
Credit: Wikimedia Commons
Fanno Creek, Durham OR

Original Description

N. Genovefae sp. nov. (Pl. I, fig. 30) 8, 9, 18.

Valve linéaire, parfois légèrement constricteé au centre, longuement rostrée aux extrémités, pôles arrondis parfois très légèrement subcapités. 20-30 µ. * 5-7 µ. Raphé droit, aréa axial lináire étroit, aréa central arrondi petit, plus ou moins régulier. Stries radiales, les 2 ou 3 derniéres parallèles aux pôles, peu distinctement lignées-ponctuées au centre, assez fortes et écartées; souvent une des stries centrales est écourtée; plus fines et serrée vers lés pôles.

Au centre 10-12 en 10 µ. 20-22 aux pôles.

  • Author
    Fusey 1951
  • Length Range
    20-30 µm
  • Width
    5-7 µm
  • Striae in 10µm
    10-12 at center valve, 20-22 at poles

Original Images

N Genovefae Orig Illus
N Genovefae Orig Descr

Cite This Page

Bishop, I, and Stancheva, R. (2017). Navicula genovefae. In Diatoms of North America. Retrieved July 21, 2018, from https://diatoms.org/species/navicula_genovefae

Responses

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