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Roderita Mitchell - Benthic Ecology

Albany State University, Georgia

Temperature Effect on Physiological Color Change of Fiddler Crabs

Fiddler crabs change color following their circadian rhythm; crabs are dark during the day and pale at night. The neurosecreted hormone that regulates color change is located in the eyestalks of fiddler crabs; when the eyestalks are removed no color change takes place. Endotherms have the ability to regulate their own body temperature whereas ectotherms have little control of internal body temperatures. Furthermore, fiddlers live in the intertidal, where they experience extreme changes in temperature. Therefore, I explored the possibility that fiddlers change color to regulate body temperature. Here, I studied temperature effect on the physiological color change on the fiddler crab Uca minax. 
I collected forty crabs from Point Lookout State Park. Then the fiddler crabs were placed in a 10oC treatment for ten minutes and photographed again. The following day crabs were exposed to 35oC temperature for ten minutes then photographed. I quantified the number of pixels from dark to light to compare differences between normal and cold, normal and hot, as well as large and small crabs. Results showed under cold conditions males get darker and females become lighter. However, under hot conditions females get darker and males become lighter. Color changes differ between size for males and females. Therefore, color change is also a product of thermoregulation in U. minax.

Funding was provided by the National Science Foundation – Research Experience for Undergraduates