1. The effect of light wavelength on hermit crab activity levels
Brendan Phillips, Adele Doucet, Andrew Mosher BIOL 3401
Mount Allison Unversity

2. Background information
Coenobita sp.
Terrestrial species
Crustaceans that inhabit empty snail shells
Possess compound eyes that vary in visual abilities
Can detect different light intensities and light wavelengths
Add picture of hermit crab

3. Previous Research Cronin and Forward 1988 Shaw and Stowe 1982
Photoreceptors typically absorbed wavelengths between 473 nm (blue light) and 515 nm (green light)
Shaw and Stowe 1982
Photoreceptors that are primarily tuned to red wavelengths
Cronin, T. W., & Forward, R. B The visual pigments of crabs. Journal of Comparative Physiology A, 162,

4. Purpose
Examine whether different light wavelengths will affect activity levels in hermit crabs
Light treatment groups
No Light
White Light
Blue Light
Red Light
Talk about shell research being main concern/gap in knowledge

5. Hypotheses
Ho: Different light wavelengths will not affect hermit crab activity
Ha: Different light wavelengths will affect hermit crab activity
Also say our prediction

6. Predictions
Activity levels rise in the late afternoon (Ball 1968) and then peak during evening and night (Turra and Denadai 2003)
Sunset and sunrise
sun’s rays pass through more atmosphere = red-orange light rays
We predict hermit crabs will be most active under no visible light and least active under white light
Ball, E. E Activity Patterns and Retinal Pigment Migration in Pagurus (Decapoda, Paguridea). Crustaceana, 14,
Turra, A., and Denadai, M.R Daily activity of four tropical intertidal hermit crabs from Southeastern Brazil. Brazilian Journal of Biology, 63,

7. Methods Identification Light Intensity Test Activity Levels Procedure
Statistical Analysis

8. Identification
Five hermits crabs labelled with different nail polish colours

9. Light intensity
Light intensity of each colour was measured in candle/feet with light intensity measuring instrument

10. Activity Level Procedure
30 second acclimation period in new tank
Counted lines crossed for 5 minutes and noted behaviour
Each crab was subjected to each light treatment (No light, white light, blue light and red light)

11. Statistical Analysis Tested for normality and homogeneity of variances
Student’s T-test
Comparison of white and low light
One-Way ANOVA
Activity levels at different lights
Chi-Square Test
Behaviours

12. Results

13. Average number of lines crossed

14. Average number of lines crossed

16. Discussion Do not reject our null hypothesis
Overall trend was consistent with previous studies (Shaw and Stowe 1982, Frank et al. 2002)
slightly higher activity levels at blue and red light
Tendency for hermit crabs to walk around perimeter
Inconsistent with previous research (Szabo 2011)
Frank, T. M., Johnsen, S., & Cronin, T. W Light and vision in the deep-sea benthos: II. Vision in deep-sea crustaceans. Journal of Experimental Biology, 215,
Szabó, Katherine Terrestrial hermit crabs (Anomura: Coenobitidae) as taphonomic agents in circum-tropical coastal sites. Journal of Archaeological Science, 4,

17. Limitations Small sample size Introduction to novel environment
Increase in anxiety = influence activity levels
Say that large sample size will reduce variability

18. Implications
Different cues to regulate activity levels (Turra and Denadai 2003)
Tidal rhythms, temperature, circadian rhythm, and air humidity
Reduce cost of owning a hermit crab
Lower activity = lower metabolism
Save on food expenses
Turra, A., and Denadai, M.R Daily activity of four tropical intertidal hermit crabs from Southeastern Brazil. Brazilian Journal of Biology, 63,

19. Questions or comments?