Structure, development and taxonomy in the genus Pyramimonas (Prasinophyceae, Chlorophyta)
Typescript (photocopy) Thesis (PhD)-- University of Melbourne, Faculty of Science, 1984 Bibliography: leaves 114-128. A new species of Pyramimonas, P. gelidicola, isolated from Antarctic sea ice, is described. The general cytological features of this species are used to illustrate the typical struct...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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University of Melbourne
1984
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| Online Access: | http://hdl.handle.net/11343/341073 |
| Summary: | Typescript (photocopy) Thesis (PhD)-- University of Melbourne, Faculty of Science, 1984 Bibliography: leaves 114-128. A new species of Pyramimonas, P. gelidicola, isolated from Antarctic sea ice, is described. The general cytological features of this species are used to illustrate the typical structure of the genus. Reconstruction of the mitochondrion and associated organelles in P. gelidicola reveals the presence of a single reticulated mitochondrion closely associated with the chloroplast. It is proposed that a single mitochondrion may be a constant feature of species of Pyramimonas, and indeed all members of the Prasinophyceae. Examination of the fine structure of periplast scales in P. gelidicola by thin section and freeze-fracture/etch electron microscopy shows that this species has six varieties of scales arranged in tiers on the cell and flagellar surface. The attainment of a more natural image of the scales by freeze-etch of unfixed material reveals that the box scale layer adjacent the plasmalemma forms a contiguous covering over the surface of the cell. A previously unknown scale type (here termed footprint scales) was found. Observations on the regeneration of mechanically amputated flagella are used as a convenient system for studying the associated deposition of flagellar scales. The observations suggest that the layer of scales adjacent the flagellar membrane are always attached to their membrane; right from the point of sysnthesis in Golgi cisternae. The scales and the subtending membrane accumulate to form a scale reservoir in which the pentagonal scales interact forming the tesselate pattern also observed on the flagellum. The reservoir and contents are probably extruded in toto as a raft of membrane with attached scales that are transported onto the developing flagellun in the manner suggested by the "labile plate domain hypothesis" of biomembranes. It is proposed that scale-scale interactions are probably responsible for the organisation into tiers of the scales not attached directly to ... |
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