Term of Award

Summer 1999

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)


Department of Biology

Committee Chair

Jonathan Copeland

Committee Member 1

Wayne Krissinger

Committee Member 2

Alan Harvey

Committee Member 3

Patricia Humphrey


Animals are in the business of turning calories into gametes. Reproductive success depends on energetic intake. A net gain in calories to carry out everyday function and maintain a homeostatic internal environment is the fundamental basis for the survival of a species. To obtain these calories, an organism must be efficient in extracting the available nutrients from its surroundings. The fiddler crab, Uca pugilator. has adaptations on its minor claw and mouth parts which make it an efficient deposit feeder. It possesses the ability to sense where and in what concentration these calories exist.

To test what effect increasing the concentration of calories in the environment has on Uca pugilator's foraging, three types of experiments were done. The first two involved increasing the concentration of sucrose while the order of presentation was changed, these two experiments gave a feeding rate based on minor claw movements to the buccal region (the "single" dose vs. "increasing" dose experiments). In the third type of experiment, the sand crab was presented with an option to feed on different caloric sediments impregnated with sucrose (the "preference" experiment). I found that Uca pugilatoradjusts its feeding rate according to the amount of stimulus present, and chooses to feed on a more energetically favorable sediment when given the option in experiment three. Changing the concentration of the stimulant, sucrose, did alter the behavioral feeding rate. The feeding rate increased with concentration but, I observed the rate dramatically decreased at relatively high concentrations (between 2.0 and 3.0M sucrose). When a crab was presented to more than one dose, the following feeding response at the next concentration was much higher than predicted. This heightened feeding behavior from more than one presentation of stimulus is due to a post-adaptive response called sensitization.


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