The structure and function of septate junctions have been studied by ultrastructural techniques in a wide range of invertebrate phyla. Techniques have included conventional and tracer impregnated tissue thin sectioning, and freeze-fracture of both fixed and unfixed tissue. Standard and goniometer stage transmission electron microscopy has been used. Work in this study has been concentrated mainly on the lower invertebrate phyla in which the simplest forms of junction might be seen, and on the higher invertebrate phyla. This latter group is of special interest in the transition region between the invertebrate and vertebrate phyla. Six new types of septate junction and a form of tight junction have been found in invertebrate phyla and are described. Two of these new septate junctions occur in each of the phyla Coelenterata, Echinodermata and Hemichordata. The tight junction occurs in the phylum Tunicata. Further data has also been obtained on five of the six previously described types of septate junction. The distribution of all twelve types within the invertebrates and their phylogenetic relationships are discussed. Work with the goniometer stage has aided in interpreting junctional structures. The results have revealed several features of the septate junction that support the idea that it has a mainly occluding function analogous to that of the vertebrate tight junction. In addition, an anastomosing septate junction has been found in the Echinodermata which is postulated to be a structural intermediate between the invertebrate septate junction and the vertebrate tight junction. A hypothesis is proposed suggesting how the septate junction might have evolved into the vertebrate tight junction. Tricellular junctional regions of most of the septate junction types are noted and briefly described.
| Identifer | oai:union.ndltd.org:ADTP/275272 |
| Date | January 1980 |
| Creators | Green, Colin Richard |
| Publisher | ResearchSpace@Auckland |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated., http://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm, Copyright: The author |
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