• Category
  • Length Range
    15.2-42 µm
  • Width Range
    4.4-7 µm
  • Striae in 10 µm



Valves are linear-lanceolate with a narrowly rounded headpole and footpole. The axial area is lanceolate and wide. Internally, the proximal raphe ends are deflected toward a single stigmoid. Striae becomr more radiate toward the apices. In SEM, the axial area is characterized by shallow depressions (round or elongate) on the valve face.

This species has only been confirmed from Hawaii.

The striae count observed here was higher than in the original reported description, and our population covered a more narrow size range. In measuring the original plate and its scalebar, we were able to count 13-16 striae in 10 µm. We concluded discrepancy in stria measurements was due to different methods of measurement.


Gomphonema insularum is currently only known from Hawaii. This species was described from Kauai, Waimea River at junction of Kukui and Waimea Canyon trails, coll.11 January, 2012.

Original Description

Gomphonema insularum, sp nov. Figs 1–16, figure 1 is of the holotype

Valves linear with slightly convex margins. Footpole rounded in larger specimens, narrow in smaller specimens. Headpole rounded. Length 15.5–42.0 µm, breadth 4.5–7.0 µm. Striae not evidently punctate, radiate to slightly radiate from the center to the headpole, radiate to strongly radiate from the center to the footpole 9–13/10 µm. Raphe weakly undulate, proximal ends curve toward the single stigma. Axial area is broad and lanceolate, slightly tumid at midvalve, narrow at poles. Apical pore field (APF) distinct. Septa and pseudosepta present at poles.

In the SEM, striae appear composed of variously shaped areolae, including c-shaped, s-shaped, m-shaped, and apically-elongate slit-like areolae (Figs 9–11). Areolae closest to the axial area are primarily c-shaped. At the center of the valve, the axial area has a few shallow depressions, and transapically-elongate depressions appear at the internal end of most striae (Figs 9–11). Proximal raphe ends are dilated, and terminate close to one another (Figs 9, 11). Distal raphe ends are deflected away from the stigma-bearing side and extend onto the valve mantle (Figs 9, 10, 12). The raphe bisects an APF that extends onto the valve, the APF is composed of round porelli (Fig. 12). Internally, pseudosepta and helictoglossae are evident at the poles (Figs 13, 14, 16), with a flange evident on the footpole pseudoseptum (Fig. 16, compare with headpole in Fig. 14). Areolae are consistently shaped as seen through the foramina. Interstriae are robust, and a relatively wide axial area is visible (Fig. 13). Proximal raphe ends are strongly recurved, and have a flap that extends over the proximal curve (Figs 13, 15). On the slightly-raised central nodule, a transapically-elongate stigmal opening is present (Fig. 15).

Holotype: Holotype slide deposited in Bernice P. Bishop Museum, Honolulu (BISH 764122). Isotypes: JPK Collection 8304 at the University of Colorado (COLO) Type locality: Kauai, Waimea River at junction of Kukui and Waimea Canyon trails, coll.11 January, 2012. Etymology: Named for occurring on islands.

  • Author
    Kociolek, Woodward and Graeff 2016
  • Length Range
    15.2-42 µm
  • Width
    4.5-7 µm
  • Striae in 10µm

Original Images

Gomphonema Insularum  Kociolek  Woodward  Graeff 2016 Plate  Lm
Gomphonema Insularum  Kociolek  Woodward  Graeff 2016  Sem
Gomphonema Insularum  Kociolek  Woodward  Graeff 2016

Cite This Page

Polaskey, M., Vaccarino, M. (2016). Gomphonema insularum. In Diatoms of North America. Retrieved May 20, 2024, from https://diatoms.org/species/gomphonema_insularum


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