Biochemical composition, gametogenesis and reproductive ecology of the marine gastropod Crepidula convexa Say.
Item
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Title
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Biochemical composition, gametogenesis and reproductive ecology of the marine gastropod Crepidula convexa Say.
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Identifier
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AAI8801677
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identifier
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8801677
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Creator
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Aitken-Ander, Pamela A.
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Contributor
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Adviser: David R. Franz
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Date
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1987
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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, General
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Abstract
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Crepidula convexa is a filter-feeding, protandric hermaphrodite which produces large, yolky eggs. During the reproductive season (May-October) at Breezy Point, New York, females can lay 4-5 egg masses.;The male gonad is inactive from January-March. In April, mitotic activity increases as the spermatogonia enter the multiplication phase. Spermatogenesis does not begin until May. Although meiotic activity decreases by November, residual spermiogenesis may continue through the winter. There is no evidence of cytolysis of "old" sperm before onset of spermatogenesis. Small oocytes are found in the gonad of functional males. Eupyrene and apyrene sperm are produced by male C. convexa.;There is little change in the female gonad between November and February. Proliferation of oogonia and follicle cells begins in February with the onset of mitotic activity. Vitellogenesis begins between late March and early April and probably continues until November. Large, yolky oocytes, many of spawnable size, are found in the gonad all year. At the end of the reproductive season, yolky oocytes not spawned are retained in the gonad through the winter.;Seasonal and year-to-year variations occur in the protein, lipid and carbohydrate content of C. convexa. These fluctuations are correlated with the reproductive cycle. Protein, lipid and carbohydrate levels tend to increase during gonadal ripening and to decrease toward the end of the reproductive season. There is a post-reproductive feeding period in the fall during which the biochemical components tend to increase followed by a decline over the winter.;Fecundity increases with female weight, and females grow throughout the period of oviposition. Although fecundity is weight-specific, egg output per unit body weight decreases as the animals become larger. As they grow, females derive less benefit for each allocation of energy to growth. Regression analysis of data for egg output and net production indicates that females of approximately 21-21.5 mm must allocate all net production to egg output and as a consequence cannot continue to grow. C. convexa larger than 22 mm have not been collected at this site. The maximum size attained by C. convexa at a particular geographic location may be determined by energetic constraints.
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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.
