Gomphonema mexicanum

Grunow in Van Heurck 1880      Category: Asymmetrical biraphid
BASIONYM: Gomphonema mexicanum Grunow in Van Heurck 1880

Gomphonema mehleri

 

Gomphonema montezumense
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LM scalebar = 10 µm = 40 pixels.

Observations

Contributor: Pat Kociolek - March 2011
Length Range: 26-55 µm
Width Range: 9-13 µm
Striae in 10 µm: 9-11

Description

Valves are elliptical-clavate with the headpole produced slightly and broadly rostrate and footpole rounded. Axial area is straight, expanded slightly due to a shortened stria on either side of the central area. A single stigma is present in the central area. The internal opening of the stigma opening is offset from the external opening. The raphe is lateral and weakly undulate. External proximal raphe ends are dilated slightly. Striae are punctate, parallel to radiate, number 9-11 in 10 µm and are strongly radiate at the footpole. An apical pore field is present at the footpole. Septa and pseudosepta are present at the poles.

There is no evidence to support Krammer and Lange-Bertalot”s (1986) inclusion of this species within “Gomphonema clavatum Ehrenberg” (compare the forms in plate 163, Fig. 9 for G. mexicanum in that reference).

Original Description

Basionym: Gomphonema mexicanum
Author: Grunow in Van Heurck 1880
Length Range: µm
Striae in 10 µm:

Original Description

Original Images

Cite This Page:
Kociolek, P. (2011). Gomphonema mexicanum. In Diatoms of the United States. Retrieved September 18, 2017, from http://westerndiatoms.colorado.edu/taxa/species/gomphonema_mexicanum

Species: Gomphonema mexicanum

Contributor: Pat Kociolek

Reviewer: Marina Potapova

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Image Credit: Pat Kociolek

  1. Valves elliptical-clavate
  2. Headpole slightly produced, broadly rostrate
  3. Axial area straight
  4. Stigma offset

Valves are elliptical-clavate. The headpole is slightly produced and broadly rostrate, while the footpole is rounded. The stigma opening on the inside is quite offset from the external opening. Striae are punctate, parallel to radiate and strongly radiate at the footpole. Septa and pseudosepta are present at the poles.

Compare

Gomphonema mexicanum can be distinguished from G. affine by its elliptical-clavate valve shape and distinctive stigma.

Gomphonema affine

Kutzing

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.

Links & ID's

Index Nominum Algarum (INA)

California Academy of Sciences (CAS)

Gomphonema mexicanum CAS

North American Diatom Ecological Database (NADED)

NADED ID: 37163

Autecology Discussion

Habits

Size Range

1001-10,000 µm3 (ie Diatoma vulgaris)

Motility

moderately motile (e.g. Navicula tripunctata)

Attachment

prostrate (e.g. mucilage pad)
vertical (e.g. stalks)

Habitat

benthic

Colony

colonies common

EMAP Assessment

The Environmental Protection Agency (EPA) western Environmental Monitoring and Assessment Program (EMAP) study was completed during the years 2000-2004 (see citations at bottom of this page). Over 1200 streams and rivers in 12 western states (Arizona, California, Colorado, Idaho, Montana, Nevada, North Dakota, Oregon, South Dakota, Utah, Washington and Wyoming) were selected for sampling based on a stratified randomized design. This type of design insures that ecological resources are sampled in proportion to their actual geographical presence. Stratified randomized design also allows for estimates of stream length with a known confidence in several “condition classes” (good or least-disturbed, intermediately-disturbed, and poor or most-disturbed) for biotic condition, chemistry and habitat.

EMAP Distribution

Gomphonema mexicanum

Distribution

The distribution map represents the relative abundance of this Gomphonema mexicanum in the western EMAP study. Relative abundance is a measure of the proportion of cells of this species based on a "fixed count" of 300 total diatom cells counted and identified. Each of the western EMAP sample sites is shown, either with a black dot for sites where Gomphonema mexicanum was not recorded, or with a red circle indicating the relative abundance of Gomphonema mexicanum.

Note that the size of the proportional symbols varies between species to help show both abundant and rare species.

Scale for the map to the left

EMAP Response Plots

Gomphonema mexicanum

Responses

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

EMAP citations

Results are published in:

Johnson, T., Hermann, K., Spaulding, S., Beyea, B., Theel, C., Sada, R., Bollman, W., Bowman, J., Larsen, A., Vining, K., Ostermiller, J., Petersen, D. Hargett, E. and Zumberge, J. (2009). An ecological assessment of USEPA Region 8 streams and rivers. U.S. Environmental Protection Agency Region 8 Report, 178 p.

Stoddard, J. L., Peck, D. V., Olsen, A. R., Larsen, D. P., Van Sickle, J., Hawkins, C. P., Hughes, R. M., Whittier, T. R., Lomnicky, G. A., Herlihy, A. T., Kaufman, P. R., Peterson, S. A., Ringold, P. L., Paulsen, S. G., and Blair, R. (2005). Environmental Monitoring and Assessment Program (EMAP) western streams and rivers statistical summary. U.S. Environmental Protection Agency Report 620/R-05/006, 1,762 p.

Stoddard, J. L., Peck, D. V., Paulsen, S. G., Van Sickle, J., Hawkins, C. P., Herlihy, A. T., Hughes, R. M., Kaufman, P. R., Larsen, D. P., Lomnicky, G. A., Olsen, A. R., Peterson, S. A., Ringold, P. L., and Whittier, T. R. (2005). An ecological assessment of western streams and rivers. U.S. Environmental Protection Agency Report 620/R-05/005, 49 p.