Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

The scales of both the right and left eyes were measured for each specimen and the results
averaged. A few specimens had only one useful spectacle scale in the shed, so measurements in these
cases include only the one.
3.2.3 Spectacle thickness measurements
The thickness of spectacle scales were determined using a thickness gauge designed for measuring the
thickness of hard contact lenses. Some samples, including the 3 elapids, were omitted due to having
undergone biochemical analysis (presented in Chapter 4) prior to thickness measurements.
3.2.4 Analytical methods
Spectral transmittance curves were plotted for visual inspection of the spectra. The 50% cutoff
wavelengths (λ50%) were determined from the raw data of each sample. To test for species and family
differences in λ50%, Kruskal-Wallis analysis of variance on ranks was used due to potential non
normality of the data (the number of Elapid samples was too low to test for normality). Differences
between families were assessed with Dunn’s multiple comparisons. Spectacle scale thicknesses were
compared between families using the same methods. Correlations between thickness and λ50% values
was assessed with Spearman’s R correlation coefficient on ranks. For all analyses, the threshold for
statistical significance was set to a Type I error probability of 0.05. Analyses were done using the
Statistica 10 software package.
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