The effect of light wavelength on hermit crab activity levels Brendan Phillips, Adele Doucet, Andrew...
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Transcript of The effect of light wavelength on hermit crab activity levels Brendan Phillips, Adele Doucet, Andrew...
The effect of light wavelength on hermit crab activity levels
Brendan Phillips, Adele Doucet, Andrew Mosher
BIOL 3401Mount Allison Unversity
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
Previous Research
• Cronin and Forward 1988– 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
Purpose
• Examine whether different light wavelengths will affect activity levels in hermit crabs
• Light treatment groups– No Light–White Light– Blue Light– Red Light
Hypotheses
• Ho: Different light wavelengths will not affect hermit crab activity
• Ha: Different light wavelengths will affect hermit crab activity
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
Light intensity
• Light intensity of each colour was measured in candle/feet with light intensity measuring instrument
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)
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
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)
Limitations
• Small sample size• Introduction to novel environment– Increase in anxiety = influence activity
levels
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