Research Articles (Biodiversity and Conservation Biology)

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Browsing by Subject "Agulhas Bank"

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    Genetic and morphological variation of the lanternfish lampanyctodes hectoris (myctophiformes: myctophidae) off Southern Africa
    (Taylor and Francis Group, 2001) Florence, W. K.; Hulley, P. A.; Stewart, B. A.
    Genetic and morphological variation within the southern African population of Lampanyctodes hectoris was analysed. A total of 15 enzymes, encoding 22 isozyme loci, was examined (n = 327); seven were polymorphic. The percentage of polymorphic loci ranged from 13.6 to 27.3%. The mean heterozygosity was generally low and ranged from 0.003 to 0.005. Genetic divergences between specimens from four areas along the west coast of southern Africa were negligible, genetic distance values (D) ranging from 0 to 0.00011. The results showed the population of L. hectoris to be genetically invariant. Principal Component Analysis was performed separately on ratios of 13 morphometric and 6 meristic variables (n = 446), and there was evidence of extensive overlap between fish from all areas. However, discriminant analysis suggested some morphological variability within this population. Although genetically the population of L. hectoris seems to be homogenous, morphologically it appears to be variable. A combination of these results suggests that there is no clear genetic basis for the slight morphological differentiation within the population.
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    Observations on euphausiid communities of the south coast of South Africa
    (NISC (Pty) Ltd and Taylor& Francis, 1995) Gibbons, Mark J.
    A total of 24 species of euphausiid was collected during a survey along the South African south coast during January 1992. Communities over the Agulhas Bank were of low diversity and abundance and were dominated by Nycliphanes capensis. Those at the shelf-edge were of high diversity and abundance and were dominated by Euphausia recurI'll and Thysalloessa gregaria. Such high diversity may be maintained by vertical scgregation at night. Few species displayed obvious diel vertical migration, although N. capen sis may be able to maintain itself on the shelf by means of this behaviour. E. recurl'Cl appeared to feed on phytoplankton throughout the water column at night, reflecting the distribution of food.