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dc.contributor.advisorDeWitt, Thomas J.
dc.creatorGarza, Mark Isaac
dc.date.accessioned2006-04-12T16:06:20Z
dc.date.available2006-04-12T16:06:20Z
dc.date.created2005-12
dc.date.issued2006-04-12
dc.identifier.urihttp://hdl.handle.net/1969.1/3309
dc.description.abstractPhenotypic plasticity is an environmentally based change in phenotype and can be adaptive. Often, the change in an organism's phenotype is induced by the presence of a predator and serves as a defense against that predator. Defensive phenotypes are induced in freshwater physid snails in response to both crayfish and molluscivorous fish. Alternative morphologies are produced depending on which of these two predators snails are raised with, thus protecting them from each of these predators' unique mode of predation. Snails and other mollusks have been shown to produce thicker, differently shaped shells when found with predators relative to those found without predators. This production of thicker, differently shaped shells offers better protection against predators because of increased predator resistance. The first study in this thesis explores costs and limits to plasticity using the snailfish- crayfish system. I exposed juvenile physid snails (using a family structure) to either early or late shifts in predation regimes to assess whether developmental flexibility is equally possible early and late in development. Physid snails were observed to produce alternative defensive morphologies when raised in the presence of each of the two predators. All families responded similarly to the environment in which they were raised. Morphology was found to be heritable, but plasticity itself was not heritable. Morphology was found to become less flexible as snails progressed along their respective developmental pathways. In the second study, I raised physid snails with and without shell-crushing sunfish and examined the differences in shell thickness, shell mass, shell size and shell microstructural properties between the two treatment groups. Shells of snails raised with predators were found to be larger, thicker and more massive than those raised without predators, but differences in microstructure were found to be insignificant. I conclude that the observed shell thickening is accomplished by the snails' depositing more of the same material into their shells and not by producing a more complex shell composition.en
dc.format.extent1318382 bytesen
dc.format.mediumelectronicen
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherTexas A&M University
dc.subjectinducible defensesen
dc.subjectshell morphologyen
dc.subjectPhysaen
dc.subjectLepomis microlophusen
dc.subjectmorphometricsen
dc.titlePredator induced defenses in prey with diverse predatorsen
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentWildlife and Fisheries Sciencesen
thesis.degree.disciplineWildlife and Fisheries Sciencesen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberCoganto, Anthony I.
dc.contributor.committeeMemberFitzgerald, Lee
dc.type.genreElectronic Thesisen
dc.type.materialtexten
dc.format.digitalOriginborn digitalen


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