Results

Figure 1

Figure 1 shows the mean number of L. obtusata in the various habitats provided for them in the lab, with the error bars showing the standard deviation of the data.  Here the delineation between side and bottom habitats is demonstrated.  

        The data were broken down into L. obtusata residing on the sides or the bottom of the tank.  In the dark treatment there were more L. obtusata on the sides of the tank than on the bottom, but the numbers were more even for the light treatment.  More dark periwinkles settled on dark substrates and light periwinkles on light substrates on the light treatments on the side of the tank.  In the dark treatment, there were 11.9±2.1 dark periwinkles on dark backgrounds on the sides of the tank and 5.9±1.8 on the bottom.  There were 6.2±1.7 light periwinkles on dark backgrounds on the side of the tank and 5.4±1.8 on the bottom of the tank.  There were 5.7±1.8 light periwinkles on dark backgrounds on the side of the tank and 4.4±1.7 on the bottom of the tank.  There were 10.7±1.2 light periwinkles in light backgrounds on the side of the tank and 6.5±2.3 on the bottom.  For the light treatment, there were 7.3±1.6 dark periwinkles on dark backgrounds on the side of the tank and 6.7±1.9 on the bottom.  There were 3.4±1.6 dark periwinkles on light backgrounds on the side of the tank and 3.7±0.8 on the bottom.  There were 3.8±1.3 light periwinkles on dark backgrounds on the side of the tank and 4.1±1.5 on the bottom.   Finally, there were 6.5±1.9 light periwinkles on light backgrounds on the side of the tank and 6.7±2.6 on the bottom. 

 Figure 2

Figure 2 shows the total numbers of L. obtusata and their habitat selection.  The error bars represent the standard deviation.  Here, the delineation between groups of L. obtusata on similar backgrounds is clear along with the increase in means with the dark treatment. 

       The mean for the light treatment was 10.6 with an average standard deviation of 2.5 and the dark treatment had a mean of 14.2 with an average standard deviation of 2.5.  Overall more L. obtusata were on the walls of the tank during the dark treatment rather than on the black rims.  For both treatments, there are more dark and light L. obtusata on dark and light backgrounds, respectively than dark and light L. obtusata on light and dark backgrounds, respectively.  In the light treatment, there are an average of 14.1 ± 2.6 dark L. obtusata on dark backgrounds, 7.2 ± 1.8 dark L. obtusata on light backgrounds, 8 ± 1.8 light L. obtusata on dark backgrounds, and 13.2 ± 3.7 light L. obtusata on light backgrounds.  In the dark treatment, there are an average of 17.7 ± 2.5 dark L. obtusata on dark backgrounds, 11.6 ± 2.9 dark L. obtusata on light backgrounds, 10 ± 2.1 light L. obtusata on light backgrounds, and 17.2 ± 2.5 light L. obtusata on light backgrounds. 

Figure 3

Figure 3 shows the total number of L. obtusata taken in the field.  The error bars represent standard deviation. 

       The field data proved to be more significant.  There were 133 ± 3.5 dark colored L. obtusata on dark backgrounds, 6 ± 0.6 dark colored L. obtusata on light background, 15 ± 0.7 light colored L. obtusata on dark backgrounds, and 65 ± 2.0 light colored L. obtusata on light backgrounds.  A one-tailed chi-squared distribution was used in Excel (CHIDIST option) to determine significance.  The resulting p value was 1.10689E-31.  If the CHITEST option is used, the result is 1.08914E-29 since three degrees of freedom are used instead of one. 

Table 1 shows the field data and results for the chi squared test. 

Table 2 shows the lab data for the light treatment and results of the chi squared test.

Table 3 shows the lab data for the dark treatment and results of the chi squared test.

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