Biological Sciences

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The herpetology of south-east Africa.
(1966) Broadley, Donald George.; Poynton, John Charles.
No abstract available.
Abscisic acid and other hormonal effects on growth in Spirodela.
(1969) Van Staden, Johannes.; Bornman, Chris H.
The effects of abscisic acid In particular, as well well as gibberellic acid and the cytoklnlns, 6-benzyladenine, kinetin, and 6-dlmethylal lalylamlnopurine, on the growth of Spirodela oligorrhiza were investigated. Abscisic acid effectively arrested growth permanently at concentrations down to 10¯¹ mg/I. Normal growth tended to be resumed at concentrations of 10¯² and 10¯³ mg/l between nine and twelve days after treatment. A concentration of 10[-8] mg/l, however, resulted in a significant increase in dry weight at both eight, nine and twelve days after introduction into the culture medium. It is suggested that the resumption of growth twelve days after treatment at those concentrations which inhibit growth up to nine days, was due to a possible progressive inactivation of abscisic acid resulting in a lowering of its concentration to a level that is promotive. It was furthermore found that the growth response of Spirodela in terms of dry weight production over a period of eight days is proportional to the log[10] concentration of abscisic acid. It is suggested that this curve can be used as a relatively reliable and easily performed bioassay to detect amounts of abscisic acid as low as 10[-5] μg. The assay is more reliable over the range 0.01 to 10,000 μg and appears not to be affected by gibberellin, benzyladenine and kinetin. The inhibitory effect of abscisic acid on growth in Spirodela was shown to be reversed by benzyladenine, kinetin and dimethylallalylaminopurine, although they were not equally effective in doing so. Benzyladenine at 1.0 mg/l was the most effective In overcoming growth inhibition by abscisic acid. Gibberellic acid, however, proved ineffective in reversing the inhibitory effect of abscisic acid on Spirodela oligorrhiza. The apparent Increases in growth obtained in some cases may have resulted more directly from gibberellic acid stimulation than from the Interaction of gibberel lie acid with abscisic acid.
Aspects of the morphology and bionomics of Batrachomorphus cedaranus (Naude) and Lygidolon laevigatum Reut. on black wattle (Acacia mearnsii De Wild)
(1970) Connell, Allan Donovan.; Oosthuizen, Marguerite Poland.; Hepburn, G. A.
No abstract available.
Intersex in four South African racial groups in Durban.
(1970) Grace, Hatherley James.; Bain, Peter G.
Chapter I The ontogeny of sex development is introduced and a definition of the intersexual state is given. A resume of intersexes recorded in South Africa is presented together with figures showing the increased demand for cytogenetic services in the country. The motivation for this study is discussed. Chapter II The biological concept of sex is outlined together with notes on the evolution of the dioecious state in animals. Thereafter a brief account of the normal and abnormal intersex states in invertebrates and vertebrates is given. Chapter III Examples of some of the abundant references to ambisexual individuals found in the classical literature, history and mythology are listed and the status of intersexes in modern society is discussed: it does not vary much from the times of ancient Greece and Rome. Chapter IV A summary of the events which led to the establishment of cytogenetics as an independent discipline is given. The discovery of nuclear sex dimorphism is noted and methods of investigation of intersexual patients are described. A detailed description is given of cytogenetic technical. "methods, ; and leads to a diagrammatic explanation of the differential diagnosis of intersexes. This is used as a basis for the classification and accordingly a simplified, unambiguous system is proposed and defended. The sources and numbers of pat~ ients recorded in this thesis are explained. Chapter V The sex chromatin is described in detail? with a description of the methods used for its demonstration and evaluation. A pilot study of normal women of the four races established that there is no inter-racial variation in chromatin frequency. Reasons are given for disregarding nuclear appendages as an accurate indication of 'sex '. Chapter VI Embryological stage s i n the development of the human urogenital tracts are recounted after considering the mechanisms of sex determination. Pathogenesis of intersexuality is considered briefly. Chapter VII Gonadal dysgenesis of the female, including Turner's syndrome and phenotypes of both male and female are presented. The classification, pathology, aetiological and cytogenetic factors are described. Illustrative case reports and extensive discussion of the syndrome are presented. Chapter VIII The Klinefelter syndrome occurs in males with supernumerary X chromosomes; a number of chromatin negative, hypogonadal conditions mimic the syndrome: they are described, with notes on the classification, pathology, aetiology and the cytogenetic features. A series of case reports demonstrate both chromatin positive and negative types. Special reference is made to the dermatoglyphic profiles which were discovered to differentiate the XY males into two groups. Chapter IX Three syndromes, the XXX, XYY and agonadism, were not encountered in this study and are consequently not discussed. Chapter X The adrenogenital syndrome has several distinctive signs which are mimicked by induced virilization; these are described and a number of case reports are presented to illustrate the syndromes. Chapter XI Male intersexes occur in several different forms: the classification of the group is explained and a distinction is made between intersexes and those with simple, or 'pseudo-intersexual', defects. The signs of the different syndromes are detailed, together with data concerning the aetiology and cytogenetics. A series of patients' case histories is used to illustrate the various syndromes. Chapter XII Idiopathic female intersexuality is defined and a short explanation of the classification is given. The signs found in this syndrome are detailed and a single case report, which is of exceptional interest because of severe masculinization and the formation of a phallic urethra, is presented. Chapter XIII Hermaphroditism is defined and the subgroups are explained. The variability of signs is discussed and details of anatomy and histology of the genital tract are given . A single hermaphrodite was encountered during the survey and the case is described. Three other patients, all infants, were suspected of being hermaphroditic but because gonadal biopsy was not undertaken they were discharged from hospital without a diagnosis having been made. Discussion of the aetiological mechanisms is presented and the need for early diagnosis and treatment is emphasized. Chapter XIV Some of the simple genital anomalies and somatic defects which resemble intersex are mentioned and are illustrated by attenuated case reports. Chapter XV The incidence of those intersexual conditions recognizable at birth by anatomical deformity is calculated from a total population of 21,000 live births recorded during the calendar year, 1969. The incidence was very low (1:7000) and does not permit analysis of inter-racial distribution. Prevalence is calculated from the number of new patients seen by the author during 1969 in Durban. Some interesting observations were made but the primary objective, to determine whether or not intersexuality is more prevalent in the Bantu than any other race, could not be answered with certainty because of the small number of patients. Hermaphroditism was shown not to be the most common type of intersex syndrome in the Bantu. Chapter XVI An outline is given of the normal dermatoglyphic features of the finger prints and palms. Some references of the patterns in Turner's and Klinefelter's syndromes are available from the literature and are compared with the profiles of patients from this series. A distinct dimorphism was found in chromatin negative hypogonadal males and was thought to distinguish between those with congenital or acquired pathology. Normal values for South Africans have not been established satisfactorily and the urgent need for this information is stressed. Chapter XVII A general discussion of the highlights of this study of the epidemiology, clinical presentation and cytogenetics of intersexuality is given and a number of conclusions are drawn .
Radical veld improvement in South Africa with special reference to the Highland sourveld of Natal.
(1970) Edwards, Peter John.; Booysen, Pieter de Villiers.; Scott, J. D.
No abstract available.
The rock lobsters (Palinuridae) of South-East Africa, with particular reference to the life histories of Panulirus Homarus and Palinurus Delagdae.
(1970) Berry, Patrick Fleetwood.; Heydorn, A. E. F.
Abstract available in PDF file.
A review of the old world genera of Lauxaniidae (Diptera)
(1971) Stuckenberg, Brian Roy.; Bush, S. F.; Heeg, Jan.
This paper presents in key form a review of the Old World genera of Lauxaniidae. Thirteen new genera are erected, three genera are placed in synonymy, four subgenera are given generic status, and one genus is transferred from the Heleomyzidae. The development of lauxaniid generic classification is reviewed and a total of 126 recognised genera is obtained. An account is given of the regional distribution of Lauxaniidae; three main faunal aggregates are distinguished, namely the Neotropical, Holarctic and Old World tropical. The validity of certain characters for generic classification is discussed, and the suggestion is made that trigonometopine forms have evolved polyphyletically as adaptations for life in grass and comparable vegetation types. A division of the family into major groups of genera is considered, and a subfamily Homoneurinae is established. The validity of characters used to distinguish Cestrotus and Turriger is examined; a failure to find reliable characters results in the synonymy of the latter genus. Illustrated descriptions are given of the type-species of new genera.
Tissue culture studies on citrus and Welwitschia.
(1972) Button, James.; Bornman, Chris H.
Part I. IN VITRO CULTURE OF CITRUS EMBRYOS AND NUCELLAR ISOLATES Zygotic embryos of the Ellendale mandarin, a monoembryonic variety of citrus, were cultured on modified basal media of Murashige and Skoog (BM[1]), and White (BM[2]) , supplemented with various growth regulators and nutrient additives. The growth of immature embryos was greatly enhanced by the addition of 400 mg/l casein hydrolysate (CH) to the basal media. Coconut milk (CM) and malt extract (ME) enhanced growth to a lesser extent, while the addition of indoleacetic acid (IAA) and kinetin (KIN) at the concentrations used, was in no way beneficial. Nucellar isolates excised from abortive and normal Ellendale mandarin ovules eight to 20 weeks after anthesis, were cultured on BM[I] and BM[2] in the presence of various concentrations and combinations of IAA, indolebutyric acid, naph~haleneacetic acid (NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), KIN, CM, benzyl adenine, 6-dimethylallylamino purine, yeast extract (YE), ME, CR, adenine (AD), adenine sulphate (AS), ascorbic acid (AA), and benzylthiazole-2-oxyacetic acid. Some of the isolates which remained alive for four months did develop callus but n~ differentiation of embryoids or other structures occurred. Unfertilized ovules from 8-12-week-old Washington Navel orange fruits provided nucellar isolates which were cultured on media similar to those upon which mandarin nucelli were unsuccessfully cultured. In the case of Navel orange nucelli however, BM[1] + 400 mg/l filter-sterilized ME, and BMl + 40 mg/l AD yielded numerous pseudobulbils which later developed embryoids. Adenine (10 mg/l) was more effective than 20 mg/l which in turn was more effective than 30 mg/l. Adenine was more effective than its equivalent amount supplemented in the sulphate form except at 10 mg/l where the two forms were equally effective. Zeatin (ZE) at 0,2 mg/l did induce some pseudobulbils and embryoids, but all these treatments were less effective than 400 mg/l ME. When transferred to BM[1] + GA[3] (1 mg/l) , embryoids developed roots and later, shoots. It was necessary to remove plantlets from the GA[3]-supplemented medium shortly after the first foliage leaves developed in order to prevent the development of weak, spindly plants . Plantlets were transferred from BM[1 ]+ GA[3] to BM[1] only, and then after careful conditioning they were planted out in soil. This appears to be the first successful attempt at inducing adventive embryogenesis 1n the nucellus of unpollinated, unfertilized citrus ovules in vitro. Part II. EMBRYO AND FREE-CELL CULTURE OF WELWITSCHIA MIRABILIS Welwitschia embryos, cultured on BMI supplemented with CR, and low levels of IAA and KIN, germinated and developed leaves but not roots. Embryos cultured on BM[I] with 5,0 and 10,0 mg/l NAA produced an abundance of friable callus from the hypocotyl root axis. This callus was used for starting suspension cultures aimed at inducing vegetative embryogenesis. A number of nutritional additives and hormones were used alone and in combination at various concentrations. Cells of numerous shapes and sizes were observed but no organogenesis was apparent in either suspension cultures or in cell colonies plated out on semi-solid agar media. A closer study of cell aggregates formed in suspensions supplemented with CM + 2,4-D revealed that internal division occurred in approximately 40 per cent of the larger cells. It is suggested that this internal division may constitute the first step in embryogenesis of Welwitsahia cells in suspension culture. It is also tempting to speculate that this process, which has been reported by other researchers, is the first step 1n embryogenesis of free cells in general. Although this attempt at inducing adventive embryogenesis in cell cultures of Welwitschia was unsuccessful, some encouraging results were obtained on potentially suitable media and possible initial stages in the organization of embryoids.
'n Plantekologiese opname van Boschberg en sy omringende gebiede met spesiale verwysing na die weidingsfaktor.
(1972) Van der Walt, Pieter Toxopeus.; Grunow, J. A.
No abstract available.
A plant ecological survey of the Umfolozi Game Reserve, Zululand.
(1972) Downing, Brian Harvey.; Bayer, A. W.
A landscape unit approach based on use of airphotos was used for investigation of Deciduous Acacia Woodland in the Reserve. The approach was useful for indicating that a quantity of as few as 531 samples could be suitable for sampling woody vegetation over the large, 493 km² area, and for showing where the samples might advantageously be distributed. Use of the approach minimised the extrapolation of community boundaries for mapping purposes. Normal association analysis of the samples revealed the nine woody consociations present and provided quantitative data on species constancy and fidelity. These data were used towards explaining low levels of homogeneity within consociations, as well as some close floristic similarities found between consociations. The successful emergence of a species to dominance in a consociation was ascribed to the presence of a particular, described soil series or rock substrate. The distribution pattern of the consociations resembled a soil-vegetation catena on the landscape. The consociations were grouped into defined physiognomic categories of Open, Closed and Riverine Woodland Associations that were distributed according to three soil associations. The effects of soil factors, fire and the biota on physiognomy, notably secondary thicket encroachment, were discussed; and the relationship between climate and phenology was mentioned. A quantitative description of the grass communities based on normal analysis of stratified sample data revealed a retrogression whereby climax grasses are being replaced by mid-seral and pioneer grasses. The retrogression was ascribed to selective grazing by an increasingly large biomass of enumerated, indigenous herbivores. Some of the management recommendations offered were based on empirically calculated estimates of the weights of dry grass required annually by the grazing animals. Copies of topography, place names, geology, land surface and vegetation maps are provided. The text is supplemented by check lists of plants and animals recorded, by eight figures, 33 tables and 54 photos.
The sea turtles of South East Africa.
(1973) Hughes, George R.; Heydorn, A. E. F.
Abstract available in PDF file.
Automatic classification and ecological profiles of South-Western Transvaal Highveld grassland.
(1973) Morris, Jeffrey William.; Villiers, T. A.
Abstract available in PDF file.
Bionomics and control of the sugarcane insect Numicia viridis Muir (Homoptera: Tropiduchidae)
(1973) Carnegie, Alastair John Michael.; Bosman, Theodore.
Numicia viridis Muir (Homoptera : Tropiduchidae) is an indigenous southern African insect which was 'described in 1931 from specimens collected in Pondoland and Natal. In 1962 it became of economic importance when it was associated with damage caused to sugarcane in both Swaziland and South Africa. Affected cane turned yellow, its leaves dried off prematurely, and an abnormally large amount of trash was produced. was affected. Growth was retarded, and in extreme cases stem texture Since 1962 the insect's association with both sugarcane and alternate host plants has been investigated, and its economic importance assessed. Insectary investigations included studies of life history, developmental stages and behaviour of N. viridis and of its parasites. Two Mirid egg predators (Tytthus mundulus(Breddin)and T. parviceps (Reuter) ) were introduced from Mauritius, but neither became successfully established. Field studies included general ecology, population dynamics, movement, distribution and the development of infestations. The association of N. viridis with 12 sugarcane varieties and with grass communities formed the subject of seven field experiments. All locally grown cane varieties and most grass species could serve as host plants, but differences in egg mortality rates for different host plants were noted. Natural controlling factors were recognised, including biological agents. Of these, two useful egg parasites (Ootetrastichus ?beatus Perkins (Eulophidae) and Oligosita sp. nov. (Trichogrammatidae) were the most important. Attention was given also to chemical control, and it was found that of ten insecticides tested in large scale field experiments, dust and low volume formulations of endosulfan and mercaptothion gave very satisfactory control.
Studies on the primary phloem of Gomphocarpus physocarpus.
(1974) Botha, Christiaan Edward Johannes.; Bornman, Chris H.
Penetration of the stems and leaves of Gomphocnrpus physocarpus by the aphid, Aphis nerii was studied with light and phase microscopes. Penetration of the epidermis and ground tissue was largely intercellular, that of the phloem tissues partly intercellular and in part intracellular. Of 75 pairs of stylet tips encountered in presumably functional sieve tubes 73 were lodged in sieve tubes of the internal and adaxial phloem. Light and electron microscope investigation of the ontogeny and differentiation of the primary phloem revealed that the internal and adaxial phloem attains a more advanced stage of maturity earlier than the corresponding external and abaxial strands. Furthermore, the protoadaxial phloem sieve tubes remain functional throughout the primary stages of growth, whereas the corresponding abaxial phloem sieve plates are associated with massive deposits of definitive callose during the latter stages of primary growth. The internal and adaxial phloem was found to be capable of independent assimilate translocation in plants which had the external phloem experimentally ringbarked. Translocation in the internal and adaxial phloem of such plants was unaffected by ringbarking. The results are interpreted as indicating that a greater proportion of assimilates is translocated in the internal and adaxial phloem sieve tubes than in the external and abaxial sieve tubes. It is concluded that this governs A. nerii's preference for the internal and adaxial phloem as a prime feeding site.
Aspects of the biology and ecology of the estuarine fishes of the east coast of South Africa.
(1974) Wallace, John Henry.; Heydorn, A. E. F.
No abstract available.
Seed dormancy and germination in Protea compacta R.Br. and Leucadendron daphnoides Meisn.
(1974) Brown, Neville Arthur Claud.; Van Staden, Johannes.
The germination responses of seed to a wide variety of treatments showed that both the pericarp and the embryo contribute to the dormant condition in Protea compacta. Germination can be improved to a greater or lesser extent by scarification, high oxygen tensions, stratification and applied hormones. In Leucadendron daphnoides dormancy is mainly imposed by the pericarp which apparently acts as a barrier to oxygen diffusion to the embryo. A considerable increase in germination is brought about by scarification and high oxygen tensions applied to intact seeds. Stratification and applied hormones improve germination to a lesser extent. Leaching and light treatments fail to improve germination in both species. Attempts to characterize the major inhibitor present in seed leachates indicated that it was coumarinlike in its properties. No evidence could be found that inhibitors leached from seed were actually involved in the regulation of germination. Poor germination in both species is apparently due to the lack of germination promoters rather than to the presence of inhibitors. Germination of seed of Leucadendron daphnoides was increased by 50% chilling at 5°C and 500% by incubation in oxygen. Both these treatments brought about a four-fold increase in the level of butanol-soluble cytokinins. The latter apparently play the primary role in promoting germination. The greater effectiveness of high oxygen tensions improving germination appears to be due to the additional effect oxygen has in stimulating the production of acidic gibberellin-like substances, to a level 30 times higher than with chilling. The acidic gibberellin-like substances do not appear to have a primary role in promoting germination but their effect is additive in the presence of a threshold level of butanol-soluble cytokinins. Maximum germination does not appear to depend on phasic changes in promoter levels, but on whether an increase in the level of gibberellin-like substances coincides with an increase in the levels of butanol-soluble cytokinins. In Protea compacta the effectiveness of chilling and oxygen incubation in improving germination by approximately 50%, is apparently mediated through their effect in increasing the levels of butanol-soluble cytokinins. The latter appear to play the primary role in promoting maximum germination, which apparently does not depend on a phasic change in promoter levels.
Ultrastructure of the germinating Welwitschia mirabilis seed.
(1975) Butler, Valerie.; Bornman, Chris H.
The structure and chemical composition of quiescent Welwitschia mirabilis (Hooker fil.) seeds and resultant changes occurring during the first 7 days of germination were studied. Research was focussed on the megagametophyte and its interrelationship with the non-vascularised outgrowth produced by the embryo. This outgrowth was given the name "feeder" by Bower in 1881 who postulated that it functions as an absorptive organ. However the possibility existed that it merely fulfilled the mechanical role of anchorage. Following hydration activation of embryonic collar cells precedes that of gametophyte cells whose rate of activation is governed by relative distance from the embryo. This sequence of activation is suggestive of a stimulatory factor diffusing from the embryo into the gametophyte. Starch, protein and lipid reserves in the collar and developing feeder are consumed within 36 to 48 h. As a consequence the rapidly developing seedling is probably largely dependent on nutrient material in the gametophyte until the plumule emerges, after approximately 5 to 6 days germination. Ventral feeder cells in contact with gametophyte tissue apparently act as transfer cells, developing numerous small wall projections invested with plasmalemma which result in a much greater absorptive surface area. The large numbers of mitochondria occurring in these cells might suggest active uptake of nutrients. At the 3- to 4-day-stage the feeder and gametophyte adhere firmly. While this adherance probably facilitates translocation of nutrients it could also have the secondary function of anchoring the feeder in the gametophyte, thus providing the emerging plumule with a firm base. The apparent root cap origin of ventral feeder cells might explain the positive geotropism of the feeder, as recent work inter alia by Wilkins and Wain (1975) has shown that root cap cells may be geoperceptive. Cytochemical methods used at the light and electron microscope level suggest that reserve material within protein bodies of the embryo and gametophyte might exist as a proteincarbohydrate complex and that globoid origin might be cytoplasmic. The immediate digestion of protein body reserves in the embryo and gametophyte interface zone argues the presence of pre-existing hydrolytic enzymes laid down within the protein bodies prior to quiescence. However the enzymes responsible for reserve breakdown in deep gametophyte tissue seem to be synthesised de nova. Protein hydrolysis precedes lipid digestion which possibly indicates that some of the resulting free amino acids might be used in the de nova synthesis of lipases. Lipid bodies, microbodies, mitochondria and amyloplasts encircled with ER seem to form a complex. Fatty acids resulting from lipase action in the lipid bodies (Ching 1968) are probably converted by microbodies (glyoxysomes) to succunate (Breidenbach and Beevers 1967) which is converted to sucrose by the action of mitochondria (Cooper and Beevers 1969a, b). Excess sucrose is probably converted to starch and stored in the amyloplasts. In 5 days the mean dry mass of the gametophyte decreases by approximately 47% during which time the total amount of lipid decreases by 76.5% and protein by 14%. Although some of the hydrolysed fatty acids and amino acids are no doubt utilised in the gametophyte it is suggested that the majority of fatty acids are probably converted to sugars· which, together with free amino acids (and possibly simple peptides) are transported to and absorbed by the embryo via the feeder whence they are utilised for seedling growth.
The ecology and ethology of ball-rolling dung beetles (Coleoptera: Scarabaeidae)
(1976) Tribe, Geoffrey Darryl.; Fietcher, D. J. C.; Crewe, R. M.
Abstract available in PDF.
Seed production studies with weeping lovegrass Eragrostis curvula (Schrad.) Nees.
(1976) Field-Dodgson, John Robert Clive.; Tainton, Neil M.
No abstract available.
Phytosociology of the Namib Desert Park, South West Africa.
(1976) Robinson, Ernest Richard.; Breen, Charles Mackie.
The geology, topography, soils and climate of the Namib Desert Park south of 23 S. Lat. are described briefly. The vegetation was investigated using the techniques of the Zurich - Montpellier school of phytosociology. Floristic and other site data were collected from 472 sites in the standard Braun - Blanquet manner and the techniques are described in some detail. These data are presented by means of phytosociological tables and detailed descriptions of each community. A total of 34 noda, communities and sub-communities, were delimited in the study area and the floristic and ecological relationships of these are discussed. Only a few of the communities can be assigned to syntaxa from other parts of the world or southern Africa because most of the Namib Desert communities seemed too different to be compared to associations from North Africa, the Middle East, South America or Australia on more than a superficial, structural basis. Very few data from other arid or semi-arid areas in southern Africa have received formal phytosociological treatment and there is therefore insufficient material to draw meaningful comparisons. The "foam structure" described by Volk & Geyger (1970) was found to be widely distributed in soils of the plains of the Namib Desert, and it was shown to have a profound influence on water penetration. The effects on vegetation development are discussed. The study generated a number of questions about the vegetation and ecosystems of the Namib Desert and some recommendations are made concerning future synecological and autecological studies. A list of species and synonyms of the names of all higher plants recorded in the study area are given in Appendix I. It is concluded that the Braun - Blanquet method is efficient in terms of time required to collect data which can be used for a number of purposes, but that a classification of vegetation ' should be followed up by autecological and detailed synecological studies of species (particularly those which characterize communities) and individual communities to determine the controlling factors more precisely and to enable more accurate predictions concerning the effects of management programmes to be made.

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