Item – Theses Canada

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OCLC number
54906337
Link(s) to full text
LAC copy
LAC copy
Author
Smith Brillant, Martha,1971-
Title
Postingestive sorting of particles within the sea scallop Placopecten magellanicus (Gmelin).
Degree
Ph. D. -- University of New Brunswick, 2001
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [2003]
Description
2 microfiches.
Notes
Includes bibliographical references.
Abstract
Suspension-feeding bivalves feed on a mixture of particles which fluctuate dramatically in quality and quantity over time. Bivalves are adapted to deal with such a diet by sorting particles both before and after ingestion to increase the energy value of the food ingested and to reduce energy losses associated with digestion. Preingestive selection has been well studied but postingestive sorting in intact bivalves has been confirmed for only a few species. Theoretically, postingestive selection may occur by preferentially directing certain particles to the digestive gland for intracellular digestion or by retaining certain particles within the gut longer than others to enhance extracellular digestion. However, the role of particle characteristics in postingestive selection has not been established. The objectives of this research were to determine if the sea scallop, 'Placopecten magellanicus' (Gmelin), has the ability to sort particles within the gut and to determine the effects of particle characteristics (both physical and chemical properties) on particle processing. Experiments with radiolabelled algae and beads were used to confirm the ability of scallops to sort particles within the stomach. The role of particle characteristics was examined by feeding scallops mixtures of particles of different sizes, densities or chemical properties and comparing their gut retention times. Scallops retained larger beads (20 [mu]m) longer than smaller beads (5 [mu]m), and lighter beads (1.05 g ml-1) longer than denser beads (2.5 g ml-1). Furthermore, beads coated with protein were retained longer than uncoated beads and live algae were retained longer than dead algae. The ability of scallops to pass small, dense particles through the gut quickly may be beneficial as most suspended inorganic material is small and dense. Also, the ability to distinguish between particles on the basis of subtle chemical cues would enable scallops to preferentially retain particles of higher food quality longer than those of poor quality. These abilities would work in concert in the natural environment to allow scallops to increase the amount of energy derived from their food supply while minimizing energetic costs associated with digestion. This research constitutes the first quantitative analysis of the effects of particle size, density and chemical composition on particle processing within intact bivalves.
ISBN
0612681645
9780612681644