Chloroplast retention in Elphidium excavatum (Terquem).
Item
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Title
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Chloroplast retention in Elphidium excavatum (Terquem).
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Identifier
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AAI9997084
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identifier
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9997084
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Creator
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Correia, Maria Jose Serol de Brito.
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Contributor
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Adviser: John J. Lee
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Date
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2001
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Microbiology | Biology, Oceanography
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Abstract
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Chloroplast retention by mollusks and several groups of protozoa has sparked the interest of several researchers in the last 3 decades. One of the protozoa groups found to retain chloroplasts from algae they partially digest are the foraminifera. Elphidium excavatum (Terquem) an abundant species of foraminifer in salt marsh areas was studied. Feeding experiments were done in the laboratory using several algae present in the foraminifer's natural habitat in order to ascertain the selectivity of the retaining process. Foraminifera were fed algae belonging to the diatoms, green algae and dinoflagellate groups. Results show a preferential retention of chloroplasts originating from diatoms (especially Amphora coffaeformis ). Further feeding experiments were done with the aim of testing whether "survival" time of the isolated plastids within the foraminifera was dependent on the type of chloroplast ingested. Foraminifera were fed, in the laboratory, monoalgal diets of Amphora coffaeformis (a diatom), Dunaliella salina (a green alga) and Amphidinium sp. (a dinoflagellate). Feeding was allowed to continue for a weeks after which the foraminifera were cleaned and kept in medium without any algal food particles. Weekly samples of the foraminifera were observed using a confocal laser scanning microscope (CSLM) and the number of chloroplasts retained by individual counted. Isolated chloroplasts were retained inside the foraminifer for at least 8 weeks and possibly up to 20 weeks. When compared to green algae (6 weeks) or dinoflagellate (4 weeks), diatom chloroplasts (9 weeks) were retained for longer periods of time under starvation of the foraminifera. Fine structure analysis of individuals fed different algal groups and of individuals fixed immediately after collection from the field were also performed. Transmission Electron Microscopy shows that the only chloroplasts retained belong probably to diatoms and that chloroplasts of green algae and dinoflagellates are not retained. The results from these three sets of experiments suggest that, just as has been shown for the ascoglossan mollusk Elysia chlorotica, chloroplasts from chromophitic algae are better suited for survival in a symbiotic host away from the algal nucleus.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
