Effects of Humidity on Locomotion in the common garden snail ( Helix aspersa )

1. Effects of Humidity on Locomotion in the common garden snail (Helix aspersa) Marissa Hackman, Hannah Kienzle, Alanna MacDonald & Jessica Browne

2. Introduction • Taxis vs. Kinesis • Dry vs. Humid environments for snails • Strategies for water conservation • epiphragm • reducing mucus production (i.e. moving less)

3. Introduction Purpose • To determine how humidity affects the locomotion of the land snail (Helix aspersa)

4. Hypothesis • The snails should show a preference for the moist environment due to the dangers of being in arid conditions • More arid environments should result in slower speeds for snails due to lower mucus production and the possible formation of the epiphragm

5. Methods • Two main experimental set-ups: 1. Preference Test 2. Kinesis Test • Snails soaked in warm water

6. Test Snails

7. Methods • Eight 30 minute trials • Moist, neutral, dry • Cleaned between trials • Direction of chambers reversed • Location recorded every minute Preference Test

8. Four set-ups 1. Low Humidity 2. Medium 3. High 4. Control • Three 20 minute trials • Snail path recorded Methods Kinesis Test

9. Results - Preference Test Figure 1. Mean ± standard error of average time spent Helix aspersa (N=8) spent in each environment (Moist, neutral, desiccant) • Significance determined using a chi-square test • df=2 • Significant difference between conditions was detected (p< 0.05) • Spent more time in the neutral environment • Often stationary when the desiccant section of the chamber • Epiphragm

10. Results - Kinesis Test Figure 1 – mean ± standard error of Helix aspersa velocity (N=3) in environments of varying levels of moisture (control, low, moderate, and high). • Kruskal-Wallis test • Not significantly different (p=0.183) • t-test • Dry and control (p=0.0093) • Moderate moist and control (p= 0.915) • Very moist and control (p=0.539) • Dry condition: completely stopped movement - epiphragm • Cheesecloth complications

11. Discussion Why would the snails prefer neutral and dry conditions? • This was not consistent with other findings • Inherent flaws with the “preference” test • Inactivity is more energetically favorable than moving away in poor conditions • Suggests differences in kinesis depending on humidity

12. Discussion Kinesis experiment • Snails in low humidity supported our hypothesis and the results of previous studies However: • High and moderate humidity did not increase speed • Favorable conditions give no incentive to change behaviour

13. Conclusions and Implications • Snails do not move faster in more humid environments, although they are more likely to be active than in drier environments • Suggests that desiccant could be an effective means of pest control

14. Avenues of Further Research • Testing movement over a soil substrate • Comparing slug and snail behaviour in these conditions