Dynamics of symbiont populations in the facultative chemosymbioses of thyasirid bivalves

Laurich, Jason R. (2014) Dynamics of symbiont populations in the facultative chemosymbioses of thyasirid bivalves. Masters thesis, Memorial University of Newfoundland.

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Within the family Thyasiridae, symbioses between hosts and sulphur-oxidizing bacteria are not present in all species. Bacteria that associate with thyasirids are extracellular, digested by host cells, and presumed to be facultatively symbiotic. Here, the dynamic and unstable nature of thyasirid-symbiont associations is characterized. We first describe a Thyasira cf. gouldi cryptic species complex in which some species possess symbionts, while others have lost them. Within symbiotic T. cf. gouldi species, both symbiont abundance and the nutritional importance of symbiont-derived nutrients fluctuate over yearly cycles. T. cf. gouldi symbionts are environmentally acquired, and association with host bivalves appears to result in the loss of both flagella and magnetosome chains. Finally, we show that hosts may control symbiont populations by mediating their access to reduced sulphur: exposing thyasirids to a constant source of reduced sulphur results in increased bacterial division which can result in host cell overgrowth and host mortality.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/8218
Item ID: 8218
Additional Information: Includes bibliographical references.
Department(s): Science, Faculty of > Biology
Date: October 2014
Date Type: Submission
Library of Congress Subject Heading: Symbiosis; Bivalves; Marine bacteria; Sulfur bacteria

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