Introduction

1. The Effects of Geotropic Excitation in Behavioural Orientation Mechanisms in Helix aspersaRussell Gibson, Jens Herzog, and Tony Vaillancourt

2. Introduction • Helix aspersa are negatively Geotaxic • Attempted to find re-orientation mechanism • Rarely documented in modern studies • Tested various levels of excitation • Hypothesis: H. aspersa are able to determine changes in direction relative to gravity and are capable of readjusting accordingly

3. Test Subjects • Helix aspersa: common garden snail • Same individuals used in previous lab • Found across globe • Wild individuals • Negatively geotaxic (travel against gravity) for foraging

4. H. ApsersaMovement • Many factors • Humidity • Nutritional needs • Predator evasion • Reproductive condition (include chemoreception) • Length of laboratory housing • Often negative to travel upwards on plants • Acquire as much food as possible • Negative during day, indifferent at night

5. Previous Literature • Cole 1926 • First real study of gastropod movement • Change in gravitational force acts on foot, which alters direction • Crozier 1935 • Further detail on movement • Hyman 1967 • Large review of many mollucs including gastropods • Clarke 1970 • General geotactic responses in several species • Iglesias and Castillejo 1999 • More modern field study of Helix aspersa

6. Follow-Up from Previous Material • Modification of lab design earlier in course • Used findings from earlier results to determine study parameters • e.g. slope of board • e.g. previous literature analysis

7. Materials and Methods • Limited supply of materials for geotaxis testing • Materials used • Protractors • Packing tape • Plexiglas board • String • Lab clamps and stands • Though this apparatus was constructed crudely, it served our purpose flawlessly.

8. Construction of the Apparatus • This apparatus was set up so that the surface of the Plexiglas plate remained at a constant 25° incline. • Optimal angle based on previous experiment • Protractors were placed on the under side of the plate and used to measure the angle of the snails path. • Snails placed on center of plate and allowed to move freely for a maximum of 300 seconds. • A predetermined threshold of 5cm from the origin had to be reached before the plate was rotated.

9. Methods • Goal to measure the angle travelled by the snail across the surface of the plate • Keep 25° incline at the same time • Rotate the entire surface of the Plexiglas plate clockwise without disturbing the animal. • Rotating without disturbing the animal was crucial • Clockwise rotation was consistent and optimal due to the fact that these snails all had dextral shells.

10. Methods continued... • Ten snails per angle group • String one: measure distance and positional angle from the origin. • String two: plumb-line to measure the angle of plate rotation. • 0° test served as a control to the other 9 manipulated groups. • Once the snail hit the threshold the board was rotated 0 – 90°, measured in 10° intervals.

11. Methods Cont. • All testing occurred in a climate controlled room. • Each individual snail was placed in warm shallow water prior to testing. • To eliminate trail following behaviours we wiped down the Plexiglas plate with paper towels and water. • No heavy disinfectants were used during wipe downs between testing individuals. • Testing occurred over a one week duration and every attempt was made to ensure that the same times were consistent between settings.

12. We had constructed two models to double our testing to reduce our overall lab time.

13. Results

14. Results

15. Results Significant Significant N.S. N.S.

16. Results

17. Discussion Factors for H. aspersamovement Factor Control in Study Climate-controlled lab, warmed snails in water prior to testing All individuals well fed No possible predator risk Boards wiped down with paper towel and water between trials* Snails were all recovered from wild territory (Newfoundland) • Humidity • Nutritional needs • Predator evasion • Reproductive condition (include chemoreception) • Length of laboratory housing *Not fully disinfected*

18. Reasons for moving • Therefore – H. aspersa were acting normally, responding to gravity changes we imposed • Gravitational forces act on 8 major foot muscles • Excitation causes shell/visceral mass shift, pulling on foot – snail readjusts • H. aspersawere able to determine changes in direction relative to gravity and readjusted accordingly

19. Study Errors – what possible cause?

20. 60 degree • Experiments conducted around 5:00pm-6:00pm in early November in New Brunswick • Dark outside • Cole (1926): Helix aspersaare indifferent with geotaxis at night • May have affected individual circadian rhythms

21. Similar pattern

22. 90 Degrees • Snails are travelling in a circular pattern, travelled with gravity initially before adjusting • Individuals departed from right side

23. In Conclusion • Helix aspersa travel in negatively geotaxic patterns and have mechanisms that allow them to re-orient themselves when exposed to geotaxic excitation • Estimate mechanisms are response of sensitivity to weight and pressure in foot musculature • Extreme excitation = more response

24. Future Studies and Repeat Experimentation • For repeating study • Keep trail testing times at same time every day • Thoroughly disinfect board between trials • Repeat change in response differences • Future study considerations • How do the other factors explained earlier impact re-orientation i.e. are they more influential? • Attempt same study at different incline slope angle • Analyze behaviour patterns after 90 degrees

25. Bean, B. (1984). Microbial geotaxis. Membranes and sensory transduction. pp. 163-198. Springer US. Boyle, P. R., & Boyle, P. R. (1981). Molluscs and man (pp. 26-35). London: Edward Arnold. Clarke, A. M. (1970), Geotactic responses in infra-human animals: A note on a new relationship between gravitational variables. Australian Jnl of Psychology, 22: 67–70. doi: 10.1080/00049537008255213 Cole, W. H. (1926). Geotropism and muscle tension in Helix. The Journal of General Physiology, 8(3), 253-263. Crozier, W. J. (1935). On the geotropic orientation of Helix. The Journal of General Physiology, 18(5), 659-667. Farkas, S. R., & Shorey, H. H. (1976). Anemotaxis and odour-trail following by the terrestrial snail Helix aspersa. Animal Behaviour, 24(3), 686-689. Gibson, R. and Herzog, J. (2013). Geotaxis observtions in H. aspersa. Unpublished. Guiller, A., Coutellec‐Vreto, M. A., Madec, L., & Deunff, J. (2001). Evolutionary history of the land snail Helix aspersa in the Western Mediterranean: preliminary results inferred from mitochondrial DNA sequences. Molecular Ecology, 10(1), 81-87. Hoagland, H., & Crozier, W. J. (1931). Geotropic excitation in Helix. The Journal of general physiology, 15(1), 15-28. Hyman, L. H. (1967). The Invertebrates: Volume VI, Mollusca 1. Pulmonata: Habits and Behaviour (pp 627-631). McGraw-Hill, New York Ierusalimsky, V. N., Zakharov, I. S., Palikhova, T. A., & Balaban, P. M. (1994). Nervous system and neural maps in gastropodHelixlucorum L. Neuroscience and Behavioral Physiology, 24(1), 13-22. Iglesias, J., & Castillejo, J. (1999). Field observations on feeding of the land snail Helix aspersa Müller. Journal of Molluscan Studies, 65(4), 411-423. Purchon, D. R. (1968). The biology of the Mollusca. Form and Function of the Mantle Cavity: Pulmonata. (pp 29-33) Pergamon Press. London. Stephens, G. J., & McGaugh, J. L. (1972). Biological factors related to learning in the land snail Helix aspersaMüller). Animal Behaviour, 20(2), 309-315.

26. Questions?