dc.contributor.advisor |
Morton, J. E. |
en |
dc.contributor.advisor |
Bullivant, S. |
en |
dc.contributor.author |
Nelson, Elizabeth Lynn |
en |
dc.date.accessioned |
2007-08-11T10:37:14Z |
en |
dc.date.available |
2007-08-11T10:37:14Z |
en |
dc.date.issued |
1976 |
en |
dc.identifier |
THESIS 76-166 |
en |
dc.identifier.citation |
Thesis (PhD--Zoology)--University of Auckland, 1976 |
en |
dc.identifier.uri |
http://hdl.handle.net/2292/1402 |
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dc.description |
Full text is available to authenticated members of The University of Auckland only. |
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dc.description.abstract |
The structure and function of the digestive gland of a marine gastropod, Maoricrypta monoxyla (family Calyptraeidae), were studied by light and electron microscopy. There were three cell types present in the epithelium of the tubules of the gland. Feeding experiments were carried out using blood, a digestible food material, and trypan blue, an indigestible dye. These experiments established that the main cell type, the digestive cell, was involved in the uptake of material from the tubule lumen by endocytosis. Ultrahistochemistry for acid phosphatase identified the components of an extensive lysosomal system in these cells. The intracellular digestion of ingested material occurred within this system in heterolysosomes, while indigestible material (as shown by trypan blue) accumulated in residual bodies containing lipofuscin pigment. The Golgi complex was shown to be involved in the production of lysosomal enzymes. The ultrastructure of the crypt cell strongly suggested that it was secreting a proteinaceous product which was synthesised in the extensive rough endoplasmic reticulum, and was packaged by the Golgi complex. A vacuolated cell was also described, and the possible functions of secretion and excretion were discussed. The dynamic state of the digestive gland epithelium was emphasised in this study, as the tubules were found to occur in several different morphological stages. These stages could be logically arranged to show a complete cycle of digestive activity and were as follows: Stage I immature tubules composed of low epithelial cells; Stage II absorbing tubules with columnar cells which were mainly involved in the uptake of food material; Stage III mature tubules with tall cells filled with heterolysosomes in which there was intracellular digestion of the food material; Stage IV tubules with elongated cells which were constricted to produce fragmentation spherules; Stage V tubules which were disintegrating through cell degeneration. This cycle was not related to the tidal cycle, as occurs in some bivalves. Simpler functional cycles in crypt and vacuolated cells were apparently not related to the digestive cell cycle. The numbers of dividing cells in the tubule epithelium were counted, and 80% of the divisions occurred in the crypts. The crypts were, therefore, considered to be the main sites for epithelial renewal, and for regenerative growth to replace breakdown tubules. Possible methods for this were outlined. After starvation experiments, ultrastructural changes were observed in crypt and digestive cells which were related to a cessation of, or decrease in, normal activity. Depletion of residual bodies led to a reinterpretation of some aspects of their function. As a basis for future functional studies the components of the connective tissue surrounding the gland were identified and described and included smooth muscle cells, a vascular and nervous supply, pore cells, vesicular connective tissue cells and amoebocytes. The lateral membranes of all epithelial cells exhibited a junctional complex at their apex comprising belt desmosomes, septate and gap junctions. These were studied by freeze fracture. |
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dc.language.iso |
en |
en |
dc.publisher |
ResearchSpace@Auckland |
en |
dc.relation.ispartof |
PhD Thesis - University of Auckland |
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dc.relation.isreferencedby |
UoA9921785914002091 |
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dc.rights |
Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. |
en |
dc.rights |
Restricted Item. Available to authenticated members of The University of Auckland. |
en |
dc.rights.uri |
https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm |
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dc.title |
Structure and function of a gastropod digestive gland |
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dc.type |
Thesis |
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thesis.degree.discipline |
Zoology |
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thesis.degree.grantor |
The University of Auckland |
en |
thesis.degree.level |
Doctoral |
en |
thesis.degree.name |
PhD |
en |
dc.subject.marsden |
Fields of Research::270000 Biological Sciences::270700 Ecology and Evolution::270702 Marine and estuarine ecology (incl. marine ichthyology) |
en |
dc.rights.holder |
Copyright: The author |
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dc.identifier.wikidata |
Q112839308 |
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