Diatoms of North AmericaDiatoms of North America

Navicula hodgeana

R.M.Patrick and Freese 1961

Navicula Hodgeana Guide
  • Category
    Symmetric Biraphid
  • Length Range
    15–19 µm
  • Width Range
    5–7 µm
  • Striae in 10 µm
    16–20

Identification

Navicula hodgeana LM3 Navicula hodgeana LM2 Navicula hodgeana LM1
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Description

Valves are linear to elliptic-linear with rounded apices. Striae are parallel at the center becoming slightly radiate at the apices. The central area is an indistinct part of the axial area. The lateral areas (a set of depressed surface ridges) are tightly associated with the axial area, forming a narrow straight to slightly curved “H”. Immediately adjacent the axial area, there is a longitudinal row of areolae. The axial area is raised above the valve surface and the raphe forms a continuous curve from apex to center. There is a separation in the raised axial ridge between the proximal raphe ends. The proximal raphe ends are small tear-drop pores and the fissures are indistinct. Areolae are round and number 3–5 within each stria, from the mantle to the axial area. In LM, a fine hyaline line is present next to the valve margin.

Only two specimens were observed in the type material. This species needs to be transferred to Fallacia, or possibly Pseudofallacia, but it is very rare at the type locality. Further clarification of the valve morphology is required.

Autecology

Original Description

Navicula hodgeana sp. nov. Pl. 2, Fig. 2

Valva lineari-elliptica, apicibus rotundatis. Ordo distinctus punctorum limitat aream, axialem, angustam. Area clara adest inter ordinem punctorum et strias. Area media conjungit cum area clara in media parte valvae. Apicibus mediis raphis proximis. Striis punctatis tenuiter et definite. Punctis formantibus lineas longitudinales, obscuras aliquantulum. Striis parallelis per maximam partem valvae sed Bunt radiatae leniter ad apices. Striis, 15-18 in 10 µ. Longitudo, 12-17 µ. Latitudo, 5-7 µ.

Valve linear-elliptic with rounded ends. A distinct row of puncta delimits the narrow axial area. A clear area is present between the row of puncta and the striae. The central area unites with this clear area in the central portion of the valve. The median ends of the raphe are proximate. The striae are distinctly and finely punctate. The puncta form more or less indistinct longitudinal lines. The striae are parallel throughout most of the valve, but are slightly radiate at the ends. Striae, 15-18 in 10 µ. Length, 12-17 µ. Breadth, 5-7 µ.

This species is related to Navicula dissipata Hust. (Ber. Deutsch. Bot. Ges., 61 (5) : 273, 1944; A.S., Atlas Diat., pl. 403, figs. 7-8, 1936) . The length-to-breadth ratio is similar although N. dissipata is a larger taxon. The striae frequency is the same. The clear central area is narrower in our taxon and the striae are composed of many fine puncta instead of a few large ones. The median ends of the raphe are close together as in N. dissipata. Occurrence in collection fairly numerous. This species is named after Dr. Charles Hodge, IV, who has helped in many ways in the preparation of this work.

Specimen illustrated. Station 133 (A-G.C. 8249A) . Holotype.

Type locality. Alaska, Sec. Jud. Div., Rogers-Post Monument, Barrow. Coll. L. R. Freese, 15 August 1951.

Distribution.—GEOGRAPHICAL—In addition to the type locality, found also at U. S. Geodetic Station, Station 25, Coll. L. R. Freese, 23 June 1951 (A-G.C. 8141A) ; Stream No. 1, Station 37, Coll. L. R. Freese, 25 June 1951 (A-G.C. 8153C) ; Freshwater Lake, Pt. Barrow Camp, Stations 40, Coll. L. R. Freese, 29 June 1951 (A-G.C. 8156) and 43, Coll. L. R. Freese, 29 June 1951 (A-G.C. 8159E) ; and Freshwater Lake, Barrow Village, Station 148, Coll. L. R. Freese, 18 August 1951 (A-G.C. 8262A) . ECOLOGICAL Fresh to brackish water. Holotype from scrapings of small rock submerged at edge of lagoon. pH, 7.0-7.9; temp., 4°-15° C; alk., 23-110 ppm (as CaCO3) ; hardness, 50-68 ppm (as CaCO3) ; Cl, 52-82 ppm; total Fe, 0.34-0.35 ppm. Other specimens collected from tundra pools, scrapings from pebbles in stream, algae in lake overflow, lake plankton. pH, 7.0-7.8; temp., 4°-8° C; alk., 23-110 ppm (as CaCO3) ; hardness, 50-130 ppm (as CaCO3) ; Cl, 58-82 ppm; total Fe, 0.15-0.34 ppm.

  • Author
    R.M.Patrick and Freese 1961
  • Length Range
    12–17 µm
  • Width
    5–7 µm
  • Striae in 10µm
    15–18

Original Images

Nhodgeana Orig Ill 1
Nhodgeana Orig Descr Sm 1

Cite This Page

Hamilton, P., Manoylov, K. (2012). Navicula hodgeana. In Diatoms of North America. Retrieved November 23, 2024, from https://diatoms.org/species/navicula_hodgeana1

Responses

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