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Publication Date

2013

Document Type

Honors Project

Department

Biological Sciences

Keywords

Carcinus maenas-Geographical distribution, Carcinus maenas-Variation, Claws-Measurement, Cuticle-Measurement, Invasive crab, Breakage resistance, Genetic variation, Claw

Abstract

In the last 100 years, the invasive European green crab has made a northern expansion into colder waters of the Gulf of Maine. Cold water temperature limits the deposition and sequestration of calcium carbonate in the shells of many marine organisms (Vermeij, 1993). Whether water temperature similarly affects the thickness and strength of crustacean cuticles however, is not known. A thinner cuticle could limit crushing ability of the crab's claws and therefore the organism's ability to forage. In this study, I tested for morphological (claw size and cuticle thickness) and functional differences in claw resistance to breakage and genetic variation among populations of an invasive crab over a latitudinal temperature gradient. This study revealed within individual, between individual, and regional differences in claw size, cuticle thickness and claw resistance to breakage across the introduced range of Carcinus maenas in the Gulf of Maine. In general, claw dimensions, cuticle thickness, and resistance to breakage scaled differently for crushers and cutters as the individual's size increased, as to be expected in dimorphic claw species. Crusher claws of crabs from the northern Gulf of Maine possessed smaller claw sizes, thinner cuticles and less resistance to breakage than their southern counterparts. Asymmetric dispersal of haplotypes introduced from a recent secondary invasion in the Canadian Maritimes, has contributed to increased genetic variation in the Gulf of Maine. Regionally specific haplotypes were recovered, yet C.maenas populations in the Gulf of Maine were relatively homogeneous. Both the regional differences in claw morphology and performance and genetic homogeneity among sampled populations, support that such biogeographic patterns are the result of ecophenotypic responses to diet and temperature.

Language

English

Comments

114 p. : ill. (some col.), maps. Honors project-Smith College, 2013. Includes bibliographical references (p. 85-91)

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