Gomphonema gibba

Wallace 1960      Category: Asymmetrical biraphid

Gomphonema freesei

 

Gomphonema incognitum

LM scalebar = 10 µm = 80 pixels.



Observations

Contributor: Sylvia Lee | Mark Edlund - December 2016
Length Range: 22-40 µm
Width Range: 7-8 µm
Striae in 10 µm: 10-12 in the center valve, 12-14 at the ends

Description

Valves are lanceolate-clavate and slightly asymmetric to the apical axis. The valve tapers evenly from the center to the headpole, but more markedly to the footpole. The footpole is often slightly bent. The apices of the headpole and footpole are similar in width. The axial area is narrowly lanceolate. Striae are weakly radiate at the center valve, becoming nearly parallel at the headpole and strongly radiate at the footpole. A single stigmoid is present in line with the median stria on one side of the valve. The raphe is lateral. An apical porefield is present at the footpole. Girdle bands have a single to double row of poorly arranged areolae. Length:width is 4.4 (n=17).

The specimens presented here are of the holotype population from the Escambia River, Florida. This slide was examined by Patrick and Reimer (1975) and illustrated in a line drawing. The illustration appears to have more marked tapering from the center of the valve to the headpole and more protracted apices than the specimens we observed on the holotype slide. By examining a number of specimens on the slide, we extended the size range of G. gibba previously reported by Wallace (1960, 36 μm) and Patrick and Reimer (1975, 36-39 μm).

Specimens with protracted apices at the headpole and lower length to width ratio have been reported as G. gibba. Further analysis is needed to understand the variability in valve shape and ultrastructure, as well as the distribution of this taxon.



Original Description

Basionym:
Author: J.H. Wallace 1960
Length Range: 36 µm
Width Range: 8 µm
Striae in 10 µm:

Original Description

Valvis angusti rhombeo-lanceolatis, 36 μ longis, 8 μ latis, raphe oblique. Striis medii-puncto unilaterali; central nodula distincto.

This species differs from Gomphonema ventricosum Greg. in that it lacks the orbicular central area of G. ventricosum and has instead a lanceolate axial area. The apex of G. ventricosum is broader than the base, while the apex and the base in this species are similar. In G. ventricosum the stigma is near the center of the valve and in this species the stigma approximates the end of the stria.

Original Images


Cite This Page:
Lee, S., and Edlund, M. (2016). Gomphonema gibba. In Diatoms of the United States. Retrieved June 25, 2017, from http://westerndiatoms.colorado.edu/taxa/species/gomphonema_gibba

Species: Gomphonema gibba

Contributor: Sylvia Lee | Mark Edlund

Reviewer: Sarah Spaulding

Citations

Patrick, R.M. and Reimer, C.W. (1975). The Diatoms of the United States, exclusive of Alaska and Hawaii, V. 2. Monographs of the Academy of Natural Sciences of Philadelphia 13.

Wallace, J. (1960). New and variable diatoms. Notulae Naturae 331: 1-8.

Links & ID's

Index Nominum Algarum (INA)

Original INA

California Academy of Sciences (CAS)

Gomphonema gibba CAS

North American Diatom Ecological Database (NADED)

NADED ID: 37048

Autecology Discussion

Gomphonema gibba was collected from Escambia River, Santa Rosa County, Florida in October 1952 by Wallace, who described the sample locality as “a typical coastal plain, meandering river, bordered by swamps” and noted the presence of a salt tongue at a depth of 7 feet at the time of collection (Wallace 1960).

Similar specimens from rivers in Georgia and Virginia could not be confirmed as Gomphonema gibba because of consistently more protracted ends and lower length:width.

Images

Gomphonema gibba specimens from the holotype slide GC 4356A observed in this study.

Credit/Source: Sylvia Lee and Mark Edlund

Gomphonema gibba specimen in girdle view showing pores on girdle band (holotype slide GC 4356A).

Credit/Source: Sylvia Lee and Mark Edlund