School of Botany - Theses

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End date: 1999 × Type: Masters Research thesis × Subject: algae ×

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    Aspects of the biology and ultrastructure of prorocentrum spp. (pyrrhophyta)
    Malcolm, Stacey, M. ( 1987)
    Ultrastructural characteristics were evaluated as taxonomic determinants for several species of dinoflagellates in the Prorocentrales (Pyrrhophyta). Five species of Prorocentrum from several localities were examined using the techniques of light and electron microscopy. The organisms were described and identified by light microscopy, and certain internal features of Prorocentrum spp. cells were described using transmission electron microscopy. Specifically, the.ultrastructure of the nucleus, cytoplasm, vesicles, pusules, trichocysts, mitochondria, chloroplasts, pyrenoids, cortex (cell wall) and flagellar apparatus was examined in these organisms. The structure of the cortex in P. gracile was also examined by the technique of freeze fracture/deep etch. Most organelles were found to vary little between taxa. The ultrastructure of a few organelles, namely the pyrenoids and some features. of the cortex, varied considerably between species and are therefore considered taxonomically more useful than others. The morphology of the chondriome (mitochondrial complement) of P. minimum was established using the technique of serial sectioning. It was found to consist of a major reticulated mitochondrion and several smaller satellite mitochondria. During cytokinesis, the major portion of the chondriome is split by the cleavage furrow and approximately half of the chondriome is passed to each daughter cell. The significance of this structure and the division mechanism is discussed (Chapter Three). Aspects of the processes of mitosis (karyokinesis) and cell division (cytokinesis) are described in P. gracile and P. minimum. Both species were found to have a closed mitosis, the nuclear membrane being strongly associated with the chromosomes, and microtubules traversing channels through the nucleus, as observed for other members of this group. Kinetochore-like structures may occur in these organisms. A cell of P. gracile undergoing division is also illustrated (Chapter Four).