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

Marissa Hackman, Hannah Kienzle, Alanna MacDonald & Jessica Browne

Introduction

• Taxis vs. Kinesis

• Dry vs. Humid environments for snails

• Strategies for water conservationo epiphragmo reducing mucus production (i.e. moving less)

IntroductionPurpose• To determine how humidity affects the locomotion of the

land snail (Helix aspersa)

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

Methods● Two main experimental set-ups:

1. Preference Test

2. Kinesis Test

• Snails soaked in warm water

Test Snails

Methods

Preference Test

● Eight 30 minute trials● Moist, neutral, dry● Cleaned between

trials● Direction of chambers

reversed● Location recorded

every minute

Methods

Kinesis Test

● Four set-ups1. Low Humidity2. Medium3. High4. Control

● Three 20 minute trials● Snail path recorded

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

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

DiscussionWhy 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

DiscussionKinesis 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

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

Avenues of Further Research

• Testing movement over a soil substrate

• Comparing slug and snail behaviour in these conditions