Transcript Alanna, Jessica, Hannah, Marissa

Effects of Humidity
on Locomotion in the
common garden snail
(Helix aspersa)
Marissa Hackman, Hannah Kienzle,
Alanna MacDonald & Jessica Browne
Introduction
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Taxis vs. Kinesis
Dry vs. Humid environments for snails
Strategies for water conservation
o
o
epiphragm
reducing mucus production (i.e. moving less)
Introduction
Purpose
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To determine how humidity affects the locomotion of the
land snail (Helix aspersa)
Hypothesis
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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
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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-ups
1. Low Humidity
2. Medium
3. High
4. Control
● Three 20 minute trials
● Snail path recorded
Results - Preference Test
● 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
Figure 1.
Mean ± standard error of average time spent Helix aspersa (N=8) spent
in each environment (Moist, neutral, desiccant)
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Often stationary when the
desiccant section of the chamber
Epiphragm
Results - Kinesis Test
● 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)
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Figure 1 – mean ± standard error of Helix aspersa velocity (N=3) in
environments of varying levels of moisture (control, low, moderate, and high).
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Dry condition: completely stopped
movement - epiphragm
Cheesecloth complications
Discussion
Why would the snails prefer neutral and dry
conditions?
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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
Discussion
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Kinesis experiment
Snails in low humidity supported our hypothesis and
the results of previous studies
However:
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High and moderate humidity did not increase speed
Favorable conditions give no incentive to change
behaviour
Conclusions and Implications
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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
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Avenues of Further Research
Testing movement over a soil substrate
Comparing slug and snail behaviour in these
conditions