Browsing by Author "Waldron, M"

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    Annual ring validation of the South African sardine Sardinops sagax using daily growth increments.
    (Taylor & Francis, 1998) Waldron, M
    A total of 21 sardine Sardinops sagax otoliths, collected in winter and spring 1994, were examined with a scanning electron microscope to validate growth zones using daily growth increments. Increment numbers and widths for the first, second and third annual growth zones served to back-calculate hatching dates and to validate the assumption that the identified annual rings were deposited in annual intervals. Fish appeared to have hatched throughout 1992. Annual ring deposition periods depended on the individual cases and did not correspond to exactly one year, with some fish estimated to be older than one year at the first annual ring deposition. The second growth zone contained a mean of 266 daily increments, with the second annual ring deposited between November 1993 and June 1994. The third annual ring was visible on six otoliths, and appeared to have been deposited in August and September 1994.
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    Comparison of two scanning electron microscope techniques for examining daily growth increments on fish otoliths.
    (Wiley, 1997) Waldron, M; Gerneke, D
    With a secondary detector and a backscatter detector, total primary increment counts on the same otoliths were similar, but more samples could be counted using the backscatter detector and the percentage of unreadable area was consistently lower with this technique.
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    Evidence of reduced growth rates of anchovy recruits off South Africa in 1989 and 1991.
    (Taylor and Francis, 1995) Waldron, M
    The ages of anchovy recruits sampled during winter recruitment surveys in 1985, 1989 and 1991 were determined by counting the daily growth rings on their otoliths. The growth coefficients K calculated for recruits in 1989 (1,040) and 1991 (1,180) demonstrate substantially slower growth rates for these two year-classes than for the 1985 year-class (K = 1,745). Individual variation of length-at-age was highest in 1991 and lowest in 1989. As a result of the slower growth, fish of the same length were markedly older in 1989 and 1991 than in 1985. The results are discussed with reference to environmental conditions in the three years.
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    An ultrastructural investigation of the surface microbiota present on the leaves and reproductive structures of the resurrection plant Myrothamnus flabellifolia
    (Elsevier, 2011) Moore, J P; Waldron, M; Lindsey, G G; Farrant, J M; Brandt, W F
    The leaves, flower and stems of the southern African angiosperm resurrection plant Myrothamnus flabellifolia were investigated at the ultrastructural level to determine the source of previously reported fungal contamination. Fungal mycelia and hyphae of the genera Aspergillus and Penicillium were found localized to the hydathodes of the leaves and stigmatic surfaces of the female flowers in both desiccated and hydrated specimens. A waxy bacterium of the genus Bacillus was found to colonise the waxy epidermal surfaces of the leaves and flowers which was also where fungal cells were found to be absent. It is suggested that the wax like deposits within the leaves and stems as well as over the epidermal surface prevent the growth of the fungal organisms. These fungi opportunistically invade moist surfaces, such as the floral stigmas, during periods of moisture availability and may thus negatively impact plant development.
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    An ultrastructural investigation of the surface microbiota present on the leaves and reproductive structures of the resurrection plant Myrothamnus flabellifolia
    (Elsevier, 2011) Moore, J P; Waldron, M; Lindsey, G G; Farrant, J M; Brandt, W F
    The leaves, flower and stems of the southern African angiosperm resurrection plant Myrothamnus flabellifolia were investigated at the ultrastructural level to determine the source of previously reported fungal contamination. Fungal mycelia and hyphae of the genera Aspergillus and Penicillium were found localized to the hydathodes of the leaves and stigmatic surfaces of the female flowers in both desiccated and hydrated specimens. A waxy bacterium of the genus Bacillus was found to colonise the waxy epidermal surfaces of the leaves and flowers which was also where fungal cells were found to be absent. It is suggested that the wax like deposits within the leaves and stems as well as over the epidermal surface prevent the growth of the fungal organisms. These fungi opportunistically invade moist surfaces, such as the floral stigmas, during periods of moisture availability and may thus negatively impact plant development.