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Kansas Geological Survey, Bulletin 202, pt. 1, originally published in 1971

Preliminary Report: Morphological Variation of Ostracoda from the Yankee Tank Creek Drainage Basin, Douglas County, Kansas

by Roger L. Kaesler

Department of Geology, The University of Kansas

Originally published in 1971 as part of Kansas Geological Survey Bulletin 201, pt. 1, p. 5-7. This is, in general, the original text as published. The information has not been updated. An Acrobat PDF version of the complete bulletin (7 MB) is also available.


Thirty-three samples that contained ostracodes were collected by weekly sampling of each of nine ponds for a four-week period in June and July of 1969. Measurements of eight characters from the right valves of 317 specimens of Cypridopsis vidua were analyzed with a two-level nested analysis of variance. Statistically significant (P < 0.001) geographic variation was shown by all eight characters, whereas only one character showed significant temporal variation. Samples from ponds at higher elevations contributed most to the variation, and it is suggested that ponds with high elevations may have more heterogeneous environments.

The ostracode species Cypridopsis vidua is abundant in farm ponds in the Yankee Tank Creek drainage basin of Douglas County, Kansas, where the Environmental Geology Section of the Kansas Geological Survey is coordinating a survey of many aspects of the environment. The purpose of the research described herein is to begin investigation of the hypothesis that carapace morphology of C. vidua varies consistently with environmental parameters and thus may be developed as an indicator of long-term environmental changes. The first phase of the research involves establishing patterns of geographic and temporal variation. The Yankee Tank Creek drainage basin (Fig. 1) is well suited for such a study, not only because of the work of the Kansas Geological Survey there, but also because it includes more than 30 farm ponds that are likely habitats for C. vidua. The watershed is also the site of the upland sanitary landfill of the City of Lawrence and thus may be subjected to pollution at some time in the future.

Figure 1--Map of the Yankee Tank Creek drainage basin showing the locations of the ponds sampled, the location of the sanitary landfill (SLF), permanent and intermittent streams, and the 900- and 1000-foot contours. Pond 27 was sampled, but no Cypridopsis vidua were found presumably because effluent from the sanitary landfill had polluted the pond.

Map of the Yankee Tank Creek drainage basin showing the locations of the ponds sampled, the location of the sanitary landfill, permanent and intermittent streams, and the 900- and 1000-foot contours.

Cypridopsis vidua was selected for study because of its nearly ubiquitous distribution in ponds and streams of the drainage basin and because, as a species with very broad geographic distribution, it has been included in many environmental studies both in North America and Europe. It is hoped that relationships between carapace morphology and environment will be found as a result of later phases of this research and that they will be applicable to the species wherever it occurs. Furthermore, C. vidua reproduces entirely parthenogenetically, and no males of the species have ever been found. Thus, statistical study of carapace morphology is facilitated by the absence of sexual dimorphism, which is pronounced among many species of ostracodes.

In the four-week period from June 6 to July 3, 1969, 33 samples that contained Cypridopsis vidua were collected from nine ponds (Fig. 1). Ponds were sampled each week. From these samples, 317 ostracodes were measured for each of the eight characters listed in Table 1 and illustrated in Figure 2. Where possible, ten specimens were measured from each sample. These specimens have been deposited with The University of Kansas Museum of Invertebrate Paleontology as specimens 1,007,570 through 1,007,886.

Table 1--Characters measured (see Fig. 1).

Character 1 Length of right valve
Character 2 Height of right valve
Character 3 Radius of curvature of posterior outline
Character 4 Radius of curvature of anterior outline
Character 5 Radius of curvature of anterior inner margin
Character 6 Radius of curvature of posterior inner margin
Character 7 Distance from venter to top of muscle scar pattern
Character 8 Distance from anterior margin to front of top adductor muscle scar

Figure 2--Right valve of Cypridopsis vidua showing the eight characters measured.

Right valve of Cypridopsis vidua showing the eight characters measured.

Data for each character were analyzed by a two-level nested analysis of variance in which level one was variance among samples collected each week and level two was variance among weeks for all samples (Table 2). Because not all the assumptions of analysis of variance were tested and because the assumption of normally distributed error terms was not met in every instance, results must be regarded as approximate. However, the analysis of variance is fairly insensitive to non-normality (Sokal and Rohlf, 1969, p. 377). All characters showed highly significant differences (P < 0.001) among samples collected during the same week, indicating that morphology of the carapaces of Cypridopsis vidua varies geographically among ponds in the drainage basin. Only character 5, diameter of the anterior inner margin, showed significant difference of morphology (P < 0.01) from week to week, that is, temporal variation.

Table 2--Two-level nested analysis of variance tables.

Character Level Sum of
Degrees of
F-test Variance
1 2 0.00 3.0 0.00 0.11 N.S.  
1 0.12 29.0 0.00 13.40 *** 60.48
    28.9 0.00    
0 0.09 284.0 0.00   46.74
2 2 0.00 3.0 0.00 0.36 N.S.  
1 0.04 29.0 0.00 7.30 *** 41.16
    28.9 0.00    
0 0.05 284.0 0.00   62.62
3 2 0.00 3.0 0.00 0.20 N.S.  
1 0.01 29.0 0.00 2.62 *** 14.78
    28.6 0.00    
0 0.02 284.0 0.00   87.58
4 2 0.00 3.0 0.00 2.16 N.S. 6.12
1 0.00 29.0 0.00 7.11 *** 36.53
    28.9 0.00    
0 0.00 284.0 0.00   57.35
5 2 0.01 3.0 0.00 4.92 ** 9.07
1 0.02 29.0 0.00 2.24 *** 10.40
    28.6 0.00    
0 0.08 284.0 0.00   80.53
6 2 0.00 3.0 0.00 1.76 N.S. 2.31
1 0.01 29.0 0.00 2.91 *** 16.24
    28.7 0.00    
0 0.03 284.0 0.00   81.45
7 2 0.00 3.0 0.00 0.28 N.S.  
1 0.02 29.0 0.00 6.30 *** 36.99
    28.8 0.00    
0 0.03 284.0 0.00   66.90
8 2 0.00 3.0 0.00 0.91 N.S.  
1 0.00 29.0 0.00 5.68 *** 32.94
    28.8 0.00    
0 0.07 284.0 0.00   67.50

Details of the results of Student-Newman-Keuls (SNK) a posteriori tests will be presented in a later paper. Results for character 1, length, are shown in Table 3 and more or less summarize results from all tests. Note that all samples from pond 4 are in nonsignificant subsets that do not include samples from pond 3 and pond 17. The differences cannot be easily interpreted. It was originally hypothesized that elevation of the ponds might correlate highly with environmental and, hence, morphological differences.

Table 3--Results of Student-Newman-Keuls a posteriori test. Sample numbers indicate the pond number followed by the week during which the sample was collected.

Results of Student-Newman-Keuls a posteriori test.

Geological formations in the area comprise alternating, nearly horizontal limestone and shale members all with maximum thickness of less than 15 feet. Ponds at lower elevations would in general receive (1) runoff from streams crossing a greater variety of substrates, and (2) groundwater from more members, thus representing greater lithologic variety. Insofar as environmental conditions in the ponds are affected by surface and ground water, ponds with low elevation could be expected to show greater homogenization because they receive runoff and ground water from similar but more heterogeneous areas than ponds at high elevations. This idea is supported by the fact that ponds 17 and 31 have the highest elevations in the drainage basin and pond 4 is among the highest. Other factors are no doubt operative as is shown in part by the fact that shortly after sampling for this study was completed, living ostracodes became very rare in pond 4 and soon after disappeared altogether. Study of geochemistry of the pond water and its relationships to ostracode morphology is now underway. For character 5, both pond 4 and pond 20 contributed to the significant temporal variation. This is shown by the fact that samples 4-2 and 20-2 do not belong to the same nonsignificant subsets as samples 4-5 and 20-4 in the SNK test of character 5 (not shown here).

This research was supported by the Kansas Geological Survey and by research grants from The University of Kansas Research Fund, Biomedical Sciences Support Grant No. FR-07037 to The University of Kansas, and the Wallace E. Pratt Research Fund of the Department of Geology. I am indebted to Richard B. Koepnick, Robert Evans, and John C. Waters for their help with the research. H. Meade Cadot read the manuscript and contributed to its improvement.


Sokal, R. R., and Rohlf, F. J., 1969, Biometry: W. H. Freeman and Company, San Francisco, 776 p.

Kansas Geological Survey, Ostracoda from the Yankee Tank Creek Drainage Basin
Placed on web May 7, 2009; originally published in May 1971.
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