• Category
  • Length Range
    61.8–77.1 µm
  • Width Range
    13.3–15.2 µm
  • Striae in 10 µm



Valves are lanceolate with rounded rounded apices. Striae are radiate at the center, to parallel and slightly convergent at the apices. The central area is asymmetrically rounded, while the axial area is narrow and straight. Striae on one, or both, sides of the central area are irregularly spaced. The raphe is lateral and straight. The distal raphe fissures form curved hooks onto the mantle. The proximal raphe ends form an elongated central poroid. Areolae are distinct and linear, 22-24 in 10 µm. A thickened central nodule is evident. Girdle bands are not yet defined.


Original Description

Navicula freesei sp. nov. Pl. 2, Fig. 14

Valva lanceolata valide, attenuata ad apices rotundatos. Haec species attenuata apicum dat valvae formam propriam. Area axiali angusta, distincta. Area media rotundata, asimili aliquantulum. Striis translineatis, radiatis per maximam partem valvae, apicibus leniter sed definite convenientibus. Striis sepositis plus procul circum aream mediam. Striis 5 in 10 µ ad aream mediam, 8-10 in 10 µ in reliqua valva. Longitudo, 52-78 µ. Latitudo, 12-15 µ. Valve strongly lanceolate, attenuated to the rounded ends. This attenuated appearance of the ends gives the valve a characteristic shape. Axial area narrow, distinct. Central area rounded, more or less asymmetrical. Striae cross-lineate, radiate throughout most of the valve, at the ends slightly but definitely convergent. Striae more distantly spaced about the central area. Striae 5 in 10 µ at central area, 8-10 in 10 µ. in rest of the valve. Length, 52-78 µ. Breadth, 12-15µ.

This taxon is similar to Navicula hasta var. gracilis Sky. (Philippine Jour. Sci., 61: 275, pl. 7, fig. 9, 1936) in shape of valve, structure of axial and central areas, and number of striae. It differs in the striae which in this taxon are slightly convergent at the ends whereas in Skvortzow's taxon they are radiate throughout the valve, and the length-to-breadth ratio is a little less in this taxon. This taxon is also similar to N. peregrina var. peregrinoides (A. Cl.) Cl.-Eul. (K. Svenska Vet.-Akad. Handl., ser. 4, 4 (5) : 149, 1953) from which it differs by its smaller size and shape of the central area. Occurrence in collection fairly numerous.

This taxon is named in honor of Dr. Leonard R. Freese who collected most of the diatoms considered in this paper and is co-author of the paper. Specimen illustrated.-Station 72 (A-G.C. 8188A) . Holotype.

Type locality.−Alaska, Sec. Jud. Div., pool on edge of Saltwater Lake, Pt. Barrow Camp. Coll. L. R. Freese, 14 July 1951.

Distribution.—GEOGRAPHICAL—In addition to the type locality, found also at Stream No. 2, Station 46, Coll. L. R. Freese, 30 June 1951 (A-G.C. 8162) ; Stream No. 2, Station 77, Coll. L. R. Freese, 14 July 1951 (A-G.C. 8193) . ECOLOGICAL-Fresh to brackish water. Holotype from pool on edge of Saltwater Lake. pH, 7.8; temp., 6° C. Other specimens from pool in bed of stream and from edge of stream flowing into lagoon. pH, 6.8; alk., 20 ppm (as CaCO3) ; hardness, 27 ppm (as CaCO3) ; Cl, 14 ppm; total Fe, 0.21 ppm.

  • Author
    R.M.Patrick and Freese 1961
  • Length Range
    52–78 µm
  • Width
    12–15 µm
  • Striae in 10µm
    5 in the center valve, 8–10 in the rest of valve

Original Images

Nfreesei  Orig Ill
Nfreesei  Orig Descr Sm

Cite This Page

Hamilton, P. (2011). Navicula freesei. In Diatoms of North America. Retrieved June 20, 2024, from https://diatoms.org/species/navicula_freesei


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