Gomphonema insularum

Kociolek, Woodward and Graeff 2016      Category: Asymmetrical biraphid

Gomphonema incognitum


Gomphonema johnsonii

LM scalebar = 10 µm = 80 pixels.


Contributor: Meredith Tyree | Melissa Vaccarino - December 2016
Length Range: 15-42 µm
Width Range: 4.4-7 µm
Striae in 10 µm: 13-16


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.

Original Description

Author: Kociolek, Woodward and Graeff 2016
Length Range: 15.2-42 µm
Width Range: 4.5-7 µm
Striae in 10 µm: 9-13

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.

Original Images

Cite This Page:
Tyree, M., and Vaccarino, M. (2016). Gomphonema insularum. In Diatoms of the United States. Retrieved April 21, 2018, from http://westerndiatoms.colorado.edu/taxa/species/gomphonema_insularum

Species: Gomphonema insularum

Contributor: Meredith Tyree | Melissa Vaccarino

Reviewer: Marina Potapova


Kociolek, J., Woodward, J. and Graeff, C. (2016). New and endemic Gomphonema C.G. Ehrenberg (Bacillariophyceae) species from Hawaii. Nova Hedwigia 102 (1-2): 141-171.

Links & ID's

Index Nominum Algarum (INA)


California Academy of Sciences (CAS)

North American Diatom Ecological Database (NADED)


Autecology Discussion

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.