Effects of Humidity on Locomotion in the common garden snail (Helix aspersa) Marissa Hackman, Hannah...

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