Thesis (M. Phil.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 336-368).

Using an experimental pressure chamber the rates of descent and the maximum depths of buoyancy equilibrium of some cichlid fishes were tested. Tilapia mossambica juveniles could descend to depths greater than 30 metres very rapidly. At 22°C small sub adult male fish (length ± 160 mm) could descend to a maximum buoyancy depth of 20 metres, small sub adult females to 13 metres while large adults (length ± 200 mm) of both sexes could descend to 11 metres. The fish generally take 4 to 5 days to reach their maximum equilibration depth. At 30°C mature adult male and female T.mossambica increased their maximum equilibration depth to 20 metres and at 15°C showed a decrease to a maximum depth of 6.7 metres. Temperature affects the rates of descent in a similar manner. T.rendalli can descend to 7.5 metres at 22°C. T.sparmanii can descend to 15 metres at 22°C. Hemihaplochromis philander fry and young juveniles are not affected by pressure. Adult males can descend to 16 metres at 22°C and 20 metres at 30°C. Adult females can descend to 26 metres at 22°C and 27 metres at 30°C. In T.mossambica oxygen appears to be the only gas secreted into the swimbladder to compensate for buoyancy loss. The haemoglobin of T.mossambica showed a marked Bohr and Root effect. Increased rates of descent with increased temperature are believed to be due to increased O₂ uptake, heart output etc. rather than as a direct effect of blood chemistry. The swimbladder wall of T.mossambica is extremely thin (2.8 ∕∪ m) and consequently a large amount of gas is lost through passive diffusion. Diffusion is not affected by temperature, consequently the increased secretory rates at higher temperatures are not balanced by a proportionately higher diffusion loss, thus enabling the fish to maintain a deeper buoyancy equilibrium at higher temperatures. Summary, p. 62-63.

Using a pooled panel data set from nine developing countries within the SADC region from 1992 to 2004, this paper empirically examines; firstly, the relationship between stock market development and long-term economic growth, and secondly, the macroeconomic determinants of stock market development, particularly market capitalisation as a percentage of GDP. The results suggest that there is a strong link between stock market development and economic growth, particularly through the liquidity provided by the market. The evidence obtained lends support to the view that a well-developed and functioning stock market can boost economic growth by enhancing faster capital accumulation and allowing for better resource allocation, particularly in developing countries. In terms of the macroeconomic determinants of stock market development, the results support those of Garcia and Liu (1999), in that we found the indicators of financial intermediary development, the value of shares traded as a percentage of GDP and the macroeconomic instability variable to be important determinants of stock market development.

D.Sc. (Zoology) / Please refer to full text to view abstract

International peacekeeping has gained a high profile in international relations and more so, in the post cold war era. The profound increase in the occurrence of civil wars globally and the consequent high demand for the UN to intervene has compelled the world body to delegate its peacekeeping powers to regional organisations. SADC is one of many regional organisations around the world which are faced with the challenge of developing peacekeeping capacities to resolve local conflicts. This thesis endeavours to investigate the prospects of peacekeeping in Southern Africa with specific reference to the involvement of South Africa as a regional power with the wherewithal to play a leadership role in this regard. This is done within the theoretical framework that is provided by the Realist school of thought in international relations. Furthermore, the concept of national interest as defined by Realism will be utilised to explain why countries in Southern Africa in general and South Africa in particular become involved in regional peacekeeping initiatives. The issue of whether the Republic should be involved and how much it should be involved has provoked an intense debate within the country. This debate will therefore be instructive in understanding the dynamics that influence the country's foreign policy behaviour towards the region in relation to playing a leadership role in regional peacekeeping initiatives. The central issue implicit in the debate is the fact that most of the SADC member states that are expected to contribute towards these initiatives have weak economies. This economic weakness in turn leads to the thorny issue of having to seek foreign assistance from western countries from which the region is trying to gain greater independence. This presents the region with a paradox because foreign assistance has serious implications for the SADC countries' sovereignty. It is in this context therefore, that this thesis examines economic development in individual SADC countries and in the region as a whole to establish whether they are in a position to develop a sustainable regional peacekeeping capacity. The contention of the thesis is that economic development is closely related to peacekeeping because without a sound economic base Southern Africa or any other region for that matter, will not be able to develop a viable peacekeeping capacity. On the other hand, keeping the peace in the region is itself important for economic development because it is only in a peaceful environment that economic development can take root.

Trite as it may sound, the end of the Cold War is a landmark event in the history of human-kind. As such, this thesis was motivated by some of the international and local events that have taken place since the end of the 1980s. At the international level, the end of the Cold War has encouraged the re-examination of the concept of security. In Southern Africa too, this process has been strengthened by the demise of apartheid in South Africa. Initially challenged by a few academics, the traditional conception of security which perceived the threat to 'national' security primarily in the form of external military aggression no longer enjoys the primacy it was accorded during the Cold War era. A 'new' security discourse has emerged, and even though it has not yet made inroads into many governments' policy papers, there is some realisation that people's security concerns go beyond external military aggression to the state. Proponents of this 'new' thinking make reference to people-centred or human security - the notion that people and not the state, must be the objects of security. Arising from that, they point to the existence of many phenomena which should also be accorded security status especially in developing countries where people are confronted by life-threatening challenges such as disease, poverty, famine, and other challenges which do not necessarily threaten life, but if not tackled with urgency could transform themselves into the more conventional military threats. Here reference is made to the proliferation of small arms, political instability, mass migr?tions, and so on. In a region besotted by many of the challenges mentioned above, a security conception informed by the 'new' approach seems more appropriate. The outcome of the traditional approach to security is well known to the region many millions of lives were lost and it is estimated that billions of dollars in revenue were also lost, all in the name of maintaining the security of the South African state. Seeing neighbouring states as threats to its security because they accommodated liberation movements who occasionally instigated military attacks against Pretoria, the former apartheid state through its policy of 'Total Strategy' terrorised the entire region, including the majority of citizens within South Africa. However, since the end of apartheid in 1994, the new democratically elected South African government has committed itself to help build a politically stable, more secure, economically prosperous and integrated region. Through its accession to the Southern African Development Community (SADC), a body which it once tried to undermine, South Africa has further demonstrated a commitment to tackle some of the region's problems in unison with its former adversaries. Throughout the Southern African region there is a realisation that there are more long-term benefits to be gained by working together to tackle the challenges that confront almost all the countries in the region than trying to solve problems independently. Therefore through SADC, primarily a development-oriented body, Southern African states will also seek to address the region's security concerns. Many of the region's governments seem to show an understanding that security and development are intertwined - that they are two sides of the same coin whereby one cannot be attained without the other. Much as this understanding is laudable, in practice it does not seem as if it will translate to the prominence of so-called development issues or marginal security issues. Accepting the 'new' thinking on security also implies an acceptance of a wider range of security agents. It does not mean that by widening the agenda of security to include nonmilitary threats, more tasks will follow for the 'men' in uniform. What it means is that, the military establishment should no longer be the sole agent of security. Instead, where there is no military threat, resources should be channeled to other establishments such as those of health and research in order to fight the spread of AIDS. Furthermore, departments of water, environmental affairs, and so on, should be part of the security policy-making process. In addition, civil society should also be included in the policy-making process. Notwithstanding its limitations, and without undermining inter-governmental projects, civil society can at best promote security by serving as a watch-dog over policies adopted by governments. South Africa during the era of apartheid is a classic example of how governments cannot always be entrusted with the security of ordinary citizens. However, an examination of the structure and terms of reference of the newly created SADC Organ for Politics, Defence and Security (from henceforth referred to as the Organ) reflects a preponderance of the traditional/realist approach to addressing security concerns. It was conceived by, and is primarily constituted by the traditional establishments of security, that is, the military and the police. Some of the Organ's objectives include; security and defence cooperation through conflict prevention, management and resolution and mediation of disputes and conflicts. Nowhere is it evident that others besides those from a military/police background were involved in the formation of this important body. There is also no indication as to how other dimensions of security will be attained through the Organ. All this casts doubt regarding SADC's actual commitment to a development-oriented, people-centred and people-driven security. Nonetheless, current debates on security give hope to the notion that in the future, people's overall security needs will be addressed.

The blue stingray, Dasyatis marmorata capensis is an important recreational shore angling species, especially amongst tournament anglers, in South Africa. The taxonomy and aspects of the biology of this species were investigated from specimens collected between March 1987 and May 1989, from various localities along the southern African coastline. Morphological comparisons were made between Dasyatis pastinaca, Dasyatis marmorata and the local variety. The results indicated that the local variety is different to D. pastinaca in colouration, disc length size, and vertebral and radial counts. The proposed new sub-species Dasyatis marmorata capensis is closest to Dasyatis marmorata of the north-eastern Atlantic coast, but differs in snout angle, disc length and snout to vent length. Analysis of catch per unit of effort data revealed that the blue stingray exhibits distinct seasonality. Adult and sub-adult fish undertake an annual onshore/offshore migration and invade the inshore region between spring and summer, while juveniles remain offshore and utilize this zone as a nursery area. Length-at-age and growth rates for both sexes were estimated from bands formed seasonally in the vertebral centra. The derived von Bertalanffy growth parameters indicated that females reach a greater asymptotic size (913.8 mm DW) and have a slower growth rate (K = -0.07) than males (531.8 mm DW, K = -0.17). Growth rates of juvenile captive specimens compared favourably with back calculated values, at approximately 65 mm/year, for the first year of growth. Dasyatis marmorata capensis is an aplacental viviparous elasmobranch with a well defined annual breeding cycle. Young are released , at a size of 170-200 mm DW, from October to December after a gestation period of approximately nine months. An average fecundity of 3.07 was calculated . Examination of gonadal development indicated that sexual maturity is first attained at a size of 408 and 500 mm DW in males and females, respectively, corresponding to ages 4.5 and 7 years. Size-related food habits were determined independently from three depth zones. The major prey items for each size class were directly related to the abundance of the infauna of the different depth zones. Polychaeta, amphipoda and stomatopoda were the major prey items in the offshore zone. In the nearshore zone, the dominant prey species were Balanoglossus capensis and Callianassa spp .. The high incidence of empty stomachs and the presence of prey items which occur in greatest abundance beyond the surf zone indicated that this zone is not utilized for the purposes of feeding.

The eight Lower Group chromitite layers of the Ruighoek Pyroxenite in the area west of the Pilanesberg (LGl - LG7), on the farm Zandspruit 168 JP, were sampled in borehole cores drilled through the succession. The stratigraphic succession faIls within Cameron's (980) units B to E of the Critical Zone. The lowermost layer of the Lower Group, the LG 1 chromitite, is located some 440 metres below the MG 2 (Middle Group) chromitite layer, above which the first appearance of cumulus plagioclase in the Complex is seen. By convention, this horizon is designated the top of the Ruighoek Pyroxenite in the Western Bushveld Complex. Homogeneous units of chromite-bearing orthopyroxenite (bronzitite), exhibiting inconspicuous layering defined in terms of variations in orthopyroxene grain-size host all but one of the Lower Group layers; the LG 4 chromitite layer is exposed within an olivine-rich subunit 23 metres in thickness (C₃ subunit). The cumulative thickness of chromitite is 2,92 metres or 0,8 per cent of the studied section, which is 381 metres in thickness. Minimum and maximum thicknesses of the LGl - LG7 layers exposed in drill core are 17 and 81 centimetres, respectively, with minor chromitite layers ranging between 2 and 5 centimetres in thickness. Weighted mean Cr₂0₃ contents of units B to E vary between 1,17 and 3,22 per cent, with the latter estimate representative of the D₂ subunit which hosts the LG 6 chromitite layer. The LG 6 is correlated with the Steelpoort layer of the Eastern Bushveld Complex, and varies between 76 and 81 centimetres in thickness under a large portion of the farm Zandspruit. An undisturbed succession striking N15°E and dipping 12 - 15°E is depicted within the studied area, which is bounded on the eastern side by the north-striking Frank fault. Major folding of the layered succession is evident to the north of the area, where the layering adjacent to the trace of the fault dips 35° to the southwest. Particular attention is paid in the present study to (a) the nature of chromitite layers and their host rocks, (b) the contrast between the mineral chemistry of weakly disseminated chromite and grains within massive ore layers, (c) concentrations of Cr, V, Ni, Co, Sc and Ti in orthopyroxene in relation to stratigraphic height, and levels of Sr, Ba and Zr associated with hypothetically pure, intercumulus plagioclase feldspar, and (d) possible mechanisms which induce crystallization of chromitite layers containing 50 per cent Cr₂0₃ from magma with a Cr content of less than 1 000 ppm. Electron microprobe studies of chromite in relation to mineralogical and textural environment clearly reveal that (a) the proportions of Cr and Al cations are linked to paragenesis: higher Al/Cr ratios characterize olivine-bearing domains, whereas grains intergrown with plagioclase feldspar exhibit low AI/Cr ratios, and (b) Al contents rise with a decline in Mg/(Mg + Fe²⁺) from high values to a value of 0,450, then decrease with a further decline in Mg/(Mg + Fe²⁺). The paragenetically later trend is emphasized in a large population of chromite grains which escaped early encapsulation in orthopyroxene crystals and continued to grow in the environment of intercumulus plagioclase. Within-and between-sample compositional variation of grains in silicate-rich domains is modelled in terms of in situ growth increments, diffusive homogenization of zonal structures, and residence time within interstitial melt. Fractionation trends, as measured by Mg/(Mg + Fe²⁺) ratios in whole-rock and/or microprobe studies of orthopyroxene, are reversed in relation to stratigraphic height towards the top of the B unit and in the overlying C unit. These data are supported, for example, by lower vanadium contents and higher Ni/Sc ratios in hypothetically pure orthopyroxene. Small olivine crystals in chromite-rich domains are enriched in Ni relative to coarse-grained olivine in adjacent dunite: a feature attributed to early isolation of primocrysts from magma in the former case, and in situ equilibration between olivine crystals and Ni-depleted residual melt in the latter case . Similarly, rising Ni contents and Mg/(Mg + Fe²⁺) ratios of orthopyroxene with increasing stratigraphic height in the footwall of the LG 6 chromitite layer, linked to a progressive decline in orthopyroxene grain-size, are effects which may arise out of early separation of interstitial melt from orthopyroxene cumulates. A model is thus proposed which (a) links the thickness of chromitite layers to the vertical separation between successive layers or the thickness of fine-grained orthopyroxenite in the footwall, (b) ascribes copious nucleation of chromite to liquid mixing of this footwall derived, Cr - depleted contaminant with influxes of hot, primitive magma, and (c) tenders the notion that the present modal proportion of mesostasis in the footwall of a chromitite layer serves as a reciprocal measure of the volume of fractionated exudate

The biology of southern African Myrmeleontidae and Nemopteridae (Neuroptera, Myrmeleontoidea) was studied with special emphasis on the nemopterid subfamily Crocinae. The superfamily Myrmeleontoidea is considered to be a monophyletic group derived from ancestors similar to the family Nymphidae. The Myrmeleontidae and Nemopteridae are the most highly evolved families, and the Nemopteridae have a sistergroup relationship with the other four myrmeleontoid families. Within the Nemopteridae, the Crocinae are considered more advanced than the subfamily Nemopterinae. An account of previous work on the two families is presented: literature relating to the Myrmeleontidae is catalogued in appendix 2 and publications dealing with the Nemopteridae are surveyed in the text . Biological and morphological information derived from the immature stages as well as the adults was used in the systematic study of the two families. The geographical distribution and phylogeny of the Myrmeleontoidea is discussed with particular reference to the Myrmeleontidae and Nemopteridae. The Myrmeleontidae have a world wide distribution whilst the Nemopteridae are more restricted, being limited to the arid and semi-arid regions of the world. It is concluded that the two families originated on Gondwanaland, and their present distribution is explained on the basis of evidence provided by plate tectonics. In southern Africa, the Myrmeleontidae show two distributional trends: there is a distinct western fauna including many endemics and an eastern fauna which comprises taxa with a wide distribution in central and east Africa, extending their ranges into the eastern parts of the subregion. The Nemopteridae occur predominantly on the western side of the subcontinent and over 90% of the species are endemic to southern Africa. A systematic revision of the southern African Crocinae is presented and summarized in a set of illustrated keys to the adults and larvae. There are now ten known crocin species in four genera from the subregion, four species being described for the first time in this thesis. The larvae of all ten species and the eggs of seven, have been correlated with the adults and are described. Two crocin genera, Concroce and Thysanocroce, have larvae with short prothoraxes, whilst those in Laurhervasia and Tjederia are elongated. Larvae of the first two genera live in plant detritus under rocks and in crevices whereas larvae of the latter two genera inhabit small dusty caves. These findings on the Myrmeleontidae and Nemopteridae are discussed in the context of general systematic theory, phylogeny and zoogeography.

Previous classifications of the Nepticulidae were based on species from the northern hemisphere, primarily western Europe (including the United Kingdom) and North America. The revised classification presented in the present work was developed from a study of material primarily from southern Africa, but also from Australia, Europe, North America, and the Orient. Most of the descriptive section deals with the taxonomy of the Nepticulidae of southern Africa. Nevertheless, a guide to the supraspecific classification of the family was a major aim. Cladistic methods were used to assess genealogy as far as possible. The degree to which it has been elucidated is incorporated into the classification. As a result of the study, the Nepticulidae are divided into two subfamilies. One of these subfamilies is divided into two tribes. Fifteen genera and six subgenera are recognised. Two keys are presented, one to subfamilies and tribes and the other to genera and subgenera. The species from southern Africa are included in eight genera, three of which are new. One hundred and seventeen species from southern Africa are considered. Seventy- two new species are described in this work. Of these 40 have been published and 32 appear as manuscript names. For some species described by previous workers lectotypes have been designated where appropriate. The primary types of all the known species from southern Africa have been examined. Observations on adult structure are discussed from the viewpoint of phylogenetic relationships both within the Nepticulidae and between the family and other lepidopteran groups. This has led to a re-interpretation and expansion of some aspects of nepticulid morphology. Numerical phenetic methods, which include cluster analyses and an ordination technique (principal component analysis), were used to check my personal assessment of phena. The illustrations (phenograms and ordination diagrams) provide a visual summary of phenetic relationships of as wide a range of Nepticulidae as possible. Aspects of the nature of taxonomic characters, ancestor-descendant relationships, and homoplasy are discussed. Brief comments are made on distribution, and host-plant choice and phylogeny.