Masters Degrees (Zoology)

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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 .
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.
Aspects of the biology of the caracal (Felis caracal Schreber, 1776) in the Cape Province, South Africa.
(1982) Stuart, Christopher Trevor.; Hickman, G.
Felis caracal, despite heavy hunting pressure, is common and widespread throughout the Cape Province. Caracal are considered to be the principal wild predator of domestic livestock (goats and sheep) by most farmers and hunt clubs. Scat and stomach content analysis, as well as observations, indicate that F. caracal prey primarily on small to medium-sized mammals. The feeding habits of caracal-in different areas varied, according to abundance and occurrence of prey species. Captive animals required an average of 586g of meat each day. Killing techniques varied for different sized prey items. Physical and behavioural ontogeny are described for captive born animals. A technique for determining age of F. caracal was developed from study of known-age captive caracal. Examination of females killed in the wild, captive births, and births which were back-dated indicated that although young were born throughout the year, there was a definite birth peak between October and February with the lowest point being in May/June. Caracal were distinctly sexually dimorphic in size. Six F. caracal (four females and two males) were trapped, fitted with radio-transmitters, and released at the capture sites. Animals were cumulatively tracked for a total of 164 weeks. The mean range was 24,16km². A young adult male covered approximately 138km before settling in a 48km² area. Recommendations are presented for reducing losses of domestic stock by the caracal, based on the principal of removing the problem individual rather than blanket control.
The present ecological status of the blue wildebeest (Connochaetes taurinus taurinus, Burchell, 1823) in the central district of the Kruger National Park.
(1985) Whyte, Ian John.; Hanks, John.; Joubert, S.C.J.
Abstract available in PDF.
A comparative study of agonistic behaviour in hairy-footed gerbils of the genus Gerbillurus (Shortridge, 1942)
(1987) Dempster, Edith Roslyn.; Perrin, Michael Richard.
Agonistic behaviour was investigated by means of staged encounters in three species and two subspecies of deserticolous rodents of the genus Gerbillurus Indiviuals of the species G.paeba paeba, G.paeba exilis, G. tytonis, G. setzeri, and G. vallinus were used in intraspecific and interspecific encounters. Intraspecific territoriality was tested in animals of the same sex G.paeba paeba, G. tytonis, and G. setzeri Analysis of agonistic behaviour permitted identification of four groups of behaviours in most classes of intraspecific encounters. These were "exploratory and solitary", "aggressive", "submissive", and "sexual" behaviours. Males of four species were less aggressive than females in same-sex encounters, and were dominated by females in different-sex encounters; the reverse was observed in G. setzeri. Male G. tytonis and G. setzeri were more tolerant of conspecifics in the territoriality apparatus than females were. In G. tytonis-G.p. paeba encounters a hierarchy emerged: female G.. tytonis were most aggressive, followed by female G.p. paeba, male G. tytonis, and finally male G.p. paeba. In areas of syntopy, G. tytonis displace G.p. paeba through aggressive interactions. A reduction in the level of aggression was exihibited in G.p. paeba-G. setzeri and G. tytonis-G. interactions. This result may reflect the phylogenetic divergence and selection of a different habitat by G. setzeri. G. vallinus dominated G.p. paeba, a result which may have been influenced by past experience and body size, since these two species are syntopic and G. vallinus is larger than G.p. paeba. Cluster analysis of behaviour profiles of different species and sexes revealed two groups, which agree partially with the karyology of the genus. G.p. paeba and G. tytonis formed one cluster, while G. setzeri and female G.p. exilis formed a second group. Male G.p. exilis and G. vallinus were less closely related to both groups. It is suggested that several stages in the process of speciation are represented in species of this genus . A range of social types is exhibited from solitary (G.p. paeba and G. tytonis) through semi-tolerant (G. setzeri and G. tytonis) through semi-tolerant (G. setzeri and female G.p. exilis) to tolerant (male G.p. exilis and G. vallinus). Habitat has a strong influence on social type.
The feeding ecology of nectarivorous birds in the Natal Drakensberg.
(1987) Daniels, Craig Lee.; Maclean, Gordon Lindsay.
No abstract available.
The effect of different diets on the reproduction of two species of mosquitoes, Aedes aegypti and Culex pipiens.
(1987) Spencer, Jennifer Ann.; Motara, M. A.
Larvae of Culex quinquefasciatus and Aedes aegypti were raised on five different diets and the effects thereof on various parameters was studied. The diets used were: A = Pronutro and Tastee wheat, B = Epo 1 rat cubes, C= Breeder's Dogmor puppy chunks, D = Vital Brewer's yeast powder and E (the control) = Vital dessicated liver. The following results were obtained. 1. Fecundity appeared not to be affected by diet in both species. 2. Fertility did not appear to be affected by diet either. 3. Diets C and D significantly shortened the duration of the larval stage in C. quinquefasciatus when compared with the control Diet E. In A. aegypti diets B, C and D produced larval periods that were significantly shorter than the control. 4. The pupal stage in C. quinquefasciatus in diets C and D was also. Significantly shorter than that of the control diet E. In A. aegypti only diet B produced a pupal stage that was significantly shorter than the control. 5. Larval mortality was significantly higher than the control diet E in C. quinquefasciatus in diet group A. There was no significant differences between the experimental diet groups A to D and the control, in A. aegypti. 6. Pupa 1 mortality appeared to be unaffected by larval diet in both species. 7. Larval diet did not affect adult mortality either. 8. In C. quinquefasciatus the size of the ovaries was significantly smaller than the control in diet group B. Ovary size appeared to be unaffected by larval diet in A. aegypti. 9. Sex ratio appeared to be greatly affected by larval diet. There were significantly more males than females in diets D and E in Culex quinquefasciatus and in diets C and E in Aedes aegypti. 10. Oogenesis also appeared to be affected by larval diet. In C. quinquefasciatus oogenesis was found to be slower from 36 hours PBM in diet A. In A. aegypti oogenesis was slower in diets A and B from 60 hours PBM. The rate of oogenesis in C. quinquefasciatus was also found to be slower, than that in A. aegypti.
The herpetofauna of the Owen Sitole College of Agriculture, Zululand.
(1990) Hoffmann, Leonard Andrew Charles.; Poynton, John Charles.
A herpetofaunal study was undertaken at the 670 ha Owen Sitole College of Agriculture (OSCA) near Empangeni, Zululand, from 1986 to 1988. Collecting was carried out primarily opportunistically, throughout all seasons. A total of 28 amphibian taxa and 44 reptile taxa, comprising two chelonians, one crocodylid, 13 lizards and 28 snakes, were recorded. A further 11 amphibian and 42 reptile taxa may possibly occur. The majority of amphibians and reptiles display a tropical distribution, often with enormous ranges. Nineteen (68%) amphibian taxa have tropical or quasi-tropical (Poynton 1964) zoogeographical affinities and 33 (75%) reptile taxa have tropical wide ranging or tropical east coast littoral (Bruton and Haacke 1980) zoogeographical affinities. Only one amphibian taxon and four reptile taxa, all snakes, have Cape or temperate affinities. These taxa are marginal in the region, reaching their distributional limits in Maputaland. Niche segregation of amphibians occurs primarily according to water bodies. Vegetation per se does not appear to be important, with the majority of species occurring in a savanna environment; however, three species, Leptopelis natalensis, h. mossambicus and Arthroleptis wahlbergii, appear to be sylvicolous in habits and are restricted to riverine vegetation. The vast majority of taxa are summer breeders, whereas only one, Cacosternum nanum nanum, was recorded breeding in winter too. The syrnpatry of h. natalensis and Hyperolius semidiscus was confirmed in this study, and H. semidiscus and H. argus were shown to behave as good species with specifically distinct calls. Snakes are segregated according to size, mode of life, activity patterns and food. Certain species, such as Naja mossambica, have catholic diets whereas others, such as Duberria lutrix lutrix, Aparallactus capensis and Dasypeltis scabra, are specialists. The lizard fauna is differentiated according to diet, foraging strategies and habitat preferences, including substrate and vegetation. Amphibians are unselective feeders, consuming a variety of insects. Some, namely Xenopus laevis laevis and Pyxicephalus adspersus edulis, have catholic tastes and are even cannibalistic. Snakes and amphibians constitute the main prey items of snakes, whereas most lizards, with the exception of Varanus niloticus niloticus which is a generalist, feed exclusively on arthropods, especially insects. Schismaderma carens, Bufo gutturalis, Hemidactylus mabouia mabouia, Lygodactylus caoensis capensis, Mabuya striata striata, Lamprophis fuliginosus, Causus rhombeatus, Duberria lutrix lutrix and Naja mossambica are attracted to places of human habitation either for feeding or for shelter. Many amphibians benefit from artificial water bodies. No less than 19 taxa were recorded from the fish ponds, the majority of which bred there, possibly because the waters are more stable, permanent and relatively free of predators than natural water bodies. The Leguaan Tick Aponomma exornatum was recorded parasitizing adult Varanus niloticus niloticus, and the Snake Tick A. latum was found on N. mossambica and h. rhombeatus; A. latum, with an extensive subSaharan distribution, shows no predilection for any species of snake. Pentastomids and nematodes were found in a number of snakes (Atractaspis, Telescopus, Psammophis and Causus); the life cycle implications of these organisms are that mammals and snakes are intermediate hosts, though more ecological and experimental evidence is necessary. Python sebae natalens is and Kinixys natalensis, both Red Data Book - Reptile and Amphibian species, are particularly threatened, the first due to slaughter for traditional uses, the second due to agricultural activities and frequent fires. It is recommended that both these reptiles be afforded maximum protection in the 110 ha game park, which is regularly patrolled and which is subjected to infrequent fires. Generally, however, the herpetofauna has fared well at the hands of the local people, testimony to which is the high species diversity.
A preliminary investigation into the status, distribution and some aspects of the foraging ecology of the southern ground hornbill (Bucorvus cafer) in Natal.
(1990) Knight, Gary Malcolm.; Sapsford, Colin W.; Kemp, Alan C.; Page, Bruce Richard.
A study on the distribution, status and selected aspects of the foraging ecology of B. cafer in Natal, was undertaken from January 1989 to December 1990. A census was initiated to assess the distribution of B. cafer in Natal. 436 sightings were reported from 187 locations. B. cafer occurs throughout Natal, except in the far northwestern regions. A population estimation based on this census suggest that between 300-350 B. cafer individuals exist in Natal, excluding KwaZulu regions. The large area occupied by KwaZulu and the protection of this species by Zulu folk law, suggest that the population may be considerably larger. Selected aspects of the foraging ecology of the two study groups in the Natal midlands were examined, focusing on the role that individuals play in provisioning the nestling, nest bound female and fledgling. B. cafer are predominantly carnivorous. They are able to utilise habitats used for a wide variety of agricultural practices. The major criteria, in terms of habitat selection, being a short (0.5 m) or sparse ground cover. Younger birds were less successful than older individuals at digging and probing for food. Foraging success rate of the juvenile increased from 7.2% prior to nesting, to 51.2% during nesting. The acquisition of foraging skills, particularly digging and probing, takes time and experience. Frogs were the major food item fed to the nestling and nest bound female. The presence of helpers reduced the amount of feeding by parent birds. Helpers in the stainbank group supp plied 25% of food bundles to the nest. The juvenile did not act as a helper. Subadults helped most during the periods when the demand for food delivery to the nest was highest, and at the end of the nesting period. Helpers reduced the amount of time that the dominant female spent away from the nest during incubation and early nestling phase. Once the female left the nest, the male reduced his food delivery rate. An abundance of frogs, close to the nest, enabled a single pair to adequately provision a nestling. The parent birds provisioned the fledgling until the following breeding season.
The breeding and reproductive biology of the vlei rat Otomys irroratus.
(1990) Pillay, Neville.; Willan, Kenneth Brian Ronald.; Meester, Jurgens Anthonie Jansen.
The breeding and reproductive biology of the vlei rat Otomys irroratus representing three allopatric populations (Committee's Drift, Hogsback and Karkloof) have been studied in the laboratory. The study attempted to establish whether the three populations differed in respect of selected reproductive parameters, and whether the populations are reproductively isolated from one another. The breeding biology of the Hogsback and Karkloof populations was similar while the Committee's Drift population differed from the other two in respect of its smaller litter size and increased interval between pairing and the production of the first litter. Pre-copulatory behaviour differed among populations, with a gradation of increasing intersexual aggression from Hogsback to Karkloof to Committee's Drift pairs. Postnatal growth and development patterns, as well as male reproductive morphology, were indistinguishable among the populations. Attempts at interpopulation breeding were successful. However, some hybrids died before weaning, while those that survived beyond weaning were sterile, particularly those resulting from cross-matings of Hogsback animals with individuals representing the other populations. Interpopulation pairs displayed higher levels of agonistic interaction than did the pure pairings. Growth and development and the reproductive morphology of male hybrids were indistinguishable from those of the parental populations. Interpopulation reproductive variation in o. irroratus appears to be due to a combination of environmental and phylogenetic constraints. 80th pre- and post-zygotic isolating mechanisms would impede gene flow between the populations should they meet in nature. All populations appear to be undergoing active speciation.
Physiological aspects of torpor in the fat mouse (Steatomys pratensis, Dendromurinae)
(1990) Richardson, Eleanor Judith.; Meester, Jurgens Anthonie Jansen.; Perrin, Michael Richard.; Sapsford, Colin W.
Several aspects of the physiology of the fat mouse Steatomys pratensis natalensis were studied in the laboratory using standard techniques and custom-made data-logging equipment. The fat was studied both from a morphological and functional point of view. The measurement of metabolic rates showed that euthermic S.pratensis have very low basal metabolic rates of 36% of expected, with torpor saving up to 69% of expended energy. Body temperatures, oxygen consumption, and activity patterns monitored over 24 hour periods with a data-logging system showed that Sipratensis have very low body temperatures of 31.3 to 35.0°C which fluctuate on a circadian rhythm with activity and oxygen consumption, all being lower during the day and higher at night. Torpor started very early in the morning and lasted for 5.5 to 11.7 hours. Huddling with a mate could reduce energy expenditure by 18%. Torpid body temperatures lay just above ambient from 15 to 35°C, below which all animals tried to arouse. Forced arousal at 10 to 30°C was slow and depended on ambient temperature while no mouse could arouse at O°C. Thermal conductance was 97.4 % of expected but cooling rates of dead S.pratensis were slow due to the heavy fat layer. Non-shivering thermogensis (measured after noradrenaline injection) was normal at 369% of BMR but maximum metabolism was twice as much, indicating other means of thermogenesis used additively with NST. Dissection showed extremely heavy fat deposits in the normal mammalian positions and also three additional deposits. Histological studies revealed most deposits as white fat but there was brown fat in the interscapular region. Soxhlet analysis showed an extremely wide range of body fat content from normal mammalian levels to contents higher than in hibernating rodents. Deprivation of food and water, or food alone, was found to induce torpor and cause the mice to become non-reproductive. Deprivation of water but not food, and deprivation of a cage mate, triggered torpor in only 40 - 44% of the cases studied. The mice took 5 to 12 days to lose 30% of their mass, but theoretically could survive longer. Weekly measurements showed no annual mass fluctuations in the laboratory but the mice became reproductively active mid-summer to early winter while torpor was at a maximum around late winter. All animals showed torpor, young more than adults and females more than males. It is suggested that the low body temperature and metabolism of S.pratensis may have evolved to prevent overheating caused by their inability to lose heat through the heavy fat layer. The species could then disperse into areas where their low energetic demands would permit them to compete successfully with high metabolic rate rodents.
Diet, home range and movement patterns of serval on farmland in Natal.
(1990) Bowland, Jane Mary.; Perrin, Michael Richard.; Lawson, D.
Servals (Felis serval) are rare cats occurring in the Natal midlands farmland, Drakensberg mountains and in game reserves in Zululand. They are thought to be extremely uncommon on farmland, yet are sometimes caught and killed in predator control programmes. The objectives of this study were to determine home range, habitat requirements, population density and diet of servals and thereby propose management recommendations for their conservation on farmland in the Natal midlands. Radio-telemetry was used to determine home range and habitat requirements, while diet was determined using scat analysis. Prey availability and vegetation changes in the habitat were monitored seasonally. Servals range over areas of 15-30km², but concentrate their activity in wetland areas where their preferred prey, Otomys irroratus, are most abundant. Over 90% of serval prey comprises small mammals, which occur at high density in the wetlands, but low density elsewhere in the study area. The results of this project have highlighted the importance of wetlands to farmland ecosystems.
Host-searching by Goniozus natalensis females elicited by a short- range kairomone in the frass of its natural host Eldana Saccharina.
(1990) Smith, Gary Sean.; Pammenter, Norman William.; Allison, James C. S.
Petri dish and olfactometer tests demonstrated that Goniozus natalensis (Gordh) females exhibit a host-searching response upon contact and at a short distance by olfaction, to a kairomone in the frass of its natural host Eldana saccharina (Walker). The host-searching response was found to be elicited by E. saccharina frass from a range of substrates, namely: two host plants of E. saccharina, papyrus and sugarcane, and four media: sugarcane, papyrus, and cellulose based media and a synthetic medium containing no plant material. The host-searching response was not elicited by Sesamia calamistis (Hamps) sugarcane medium frass. The sexual state and age of G. natalensis females were found to influence the host-searching behaviour. Mated females showed the behaviour in the petri dish bioassays only after completing their preoviposition time of two to three days, whilst virgin females took longer, even though their preoviposition time was found to be the same. The response to male or female produced E. saccharina sugarcane frass was not statistically different, nor was there a statistically significant preference for either frass type, given the choice. Four way olfactometer tests showed that an E. saccharina sugarcane frass odour elicited a host-searching behaviour in mated two to three day old G. natalensis females. Various solvents were tested for their ability to isolate the kairomone from E. saccharina sugarcane frass. Chloroform proved to be the best solvent when tested in petri dish and olfactometer bioassays. The preliminary results of the GC/MS analysis of the chloroform extract of E. saccharina sugarcane frass are presented. The chemicals identified are compared with chemicals identified as host location kairomones for other insect parasitoid-host studies.
Mitochondrial DNA variability between selected populations of Otomys irroratus (Muridae:Otomyinae)
(1993) Raubenheimer, Janine.; Lamb, Jennifer Margaret.; Contrafatto, Giancarlo.
An interpopulation study was done on the rodent species Otamys irroratus (Muridae:Otomyinae) using restriction fragment length Polymorphisms to examine the mitochondrial DNA (mtDNA) of 30 vlei rats (Otamys irroratus) from three South African locations and 12 Angoni vlei rats (O.angoniensis) from two locations which were included as an outgroup. The three O.irroratus Populations originated from Karkloof and Kamberg in the Natal midlands and from Rietvlei in the Southern Transvaal. Mitochondrial DNA was extracted and purified by cesium-chloride/ethidium-bromide ultracentrifugation and digested with 19 class 11 restriction endonucleases. The fragments were end-labelled with 32P-dCTP, separated by electrophoresis on horizontal 1% agarose gels and the bands detected by autoradiography. The resultant individual-specific fragment patterns were analysed using the Restsite analysis program (v 1.1; Nei and Miller, 1990) to obtain a measure of the percent sequence divergences between and within the 3 POpulations of O.irroratus as well as between this species and the outgroup. The 19 endonucleases detected 19 distinct O.irroratus mtDNA maternal lineages and 3 O.angoniensis lineages. The O.irroratus lineages were clearly geographical ly structured and most closely reflected the Avise et al. (1987) category I (phylogenetic discontinuity with spatial separation). The only exception was a possible ancestral lineage represented by single individuals from Kamberg and Karkloof. Phylogenetic affinities between the most diverse lineages found at Kamberg and most Karkloof clones appear to be consistent with the finding of Pillay et al. (1993) and Contrafatto et al. (1992b) that Kamberg O.irroratus is an incipient sibling species of Karkloof O.irroratus. The mtDNA data indicates that the O.irroratus Populations at Karkloof and Kamberg last shared a common ancestor approximately 365 000 years ago. By contrast, O.angoniensis showed no evidence of geographic mtDNA structuring and is best described by the Avise et al. (1987) category Ill, which reflects phylogenetic continuity with spatial separation. These classifications must be regarded with caution given the limited distributional range of each species covered by this investigation. The interspecific mtDNA sequence divergence between O.irroratus and O.angoniensis of 11.57% substaniates morphological, karyotypic and allozymic evidence that these two sympatric species are also sibling species and they appear to have last shared a common ancestor between 1.2 and 2.4 million years ago.
An investigation of the ichthyofaunal by-catch of the Tugela Bank prawn trawlers.
(1993) Fennessy, Sean Thomas.; De Freitas, A. J.; Van der Elst, Rudy P.
The by-catch of penaeid prawn trawlers operating on the Tugela Bank of Natal was analysed at irregular intervals for a period of three years, from May 1989 to June 1992. This was primarily in response to claims by Iinefishermen that trawlers were catching and discarding juvenile Iinefish species. Catch and effort data were recorded from 159 trawls, and catch composition data from 110 trawls, over a depth range of 20 to 45 meters. A total of 108 teleost species were identified in the by-catch, six of which comprised 80 percent of overall teleost abundance by number. Many of these fish were small-sized shoaling species, which increased their vulnerability to trawlers, and the majority were considered to be estuarine-associated. Multivariate analysis of samples showed there to be significant differences in relative abundance of species by season and depth. Annual average by-catch and discarded quantities were estimated at 400 and 315 tonnes respectively. Discard:retained catch ratios' ranged from 4.25 (± 1.19) : 1 to 15.48 (± 3.86) : 1 for shallow (20-33 meters) and deep (33-45 meters) trawls respectively. Only one important Iinefish, the squaretail kob, Argyrosomus thorpei, occurred in prawn trawl catches. These fish were spawned four to six months prior to being caught and appeared to use the Tugela Bank as a nursery area. They were seasonally abundant, occurring mostly from January to March. During these months trawling effort was generally low, as the prawns had not yet migrated offshore in quantity. Per-recruit analyses showed that the removal of these age 0 fish by trawlers reduced yield-per-recruit and spawning biomass-per-recruit values for the A. thorpei fishery. Aspects of the biology of three common sciaenids occurring in trawl catches, Johnius dussumieri, J. amblycephalus and Otolithes ruber, were investigated. Most of the fish examined were juveniles which utilised the Tugela Bank as a nursery area, owing to the existence of suitable food, and the turbid waters afforded them protection from predators. Standard biological data, such as length frequencies, lengthweight relationships and size at 50% maturity are presented. Based on the data collected and the analyses presented here, management recommendations are presented, which include the improvement of the collection of catch and effort data for the Tugela Bank prawn trawlers; communication of the results of this study to prawn trawler operators in order to encourage the reduction of trawling effort early in the year; consideration to be given to the re-surveying of Tugela Bank ichthyofaunal by-catch in the future in order to assess potential long-term effects of trawling in the area.
The distribution and abundance of the humpback dolphin (Sousa chinensis) along the Natal coast, South Africa.
(1994) Durham, Ben.; Cockcroft, Victor Gavin.; Forbes, Anthony Tonks.
Populations of the humpback dolphin in Natal, South Africa, are subject to increasing pressures including capture in the shark nets and habitat degradation, and concern has been raised about the status of the population. A minimum of 95 humpback dolphins were caught in the shark nets during the period from 1980 to 1992. Capture and sighting records of the Natal Sharks Board revealed a relatively high occurrence of humpback dolphins at Richards Bay. Elsewhere, in southern Natal, the infrequent sightings and captures were attributed to a seasonal occurrence of dolphins, possibly due to temporary movements away from resident areas. Sighting rates reported by the Natal Sharks Board has decreased by 55%from 1984-86 to 1990-92 and may reflect a decrease in the population. In a photo-identification study, searches took place in ten search areas in Natal. The sighting rates in the different areas revealed a relatively high density of humpback dolphins occurring in north central Natal, from the Tugela River to the St. Lucia estuary (including Richards Bay). This distribution correlated significantly with the turbidity of the water and the width of the inshore continental shelf, and was inversely related to the density of bottlenose dolphins. Within the northern Tugela Bank region, higher densities of dolphins were found surrounding the five river mouths and estuaries. The Natal population was estimated to be between 161 to 166 animals (95% confidence limits 134 to 229). The annual mortality due to shark net captures approximates 4,5%of the population. Various evidence, including a high mortality rate and a decrease in the annual sighting per unit effort reported by the Natal Sharks Board suggest that the humpback dolphin population in Natal is vulnerable and may be decreasing in size. A proposal is made to reduce the capture rate by relocating shark nets away from the Richards Bay harbour.
Restriction patterns of mitochondrial DNA in natural populations of the murid species Otomys irroratus.
(1994) Rimmer, Alison.; Lamb, Jennifer Margaret.; Contrafatto, Giancarlo.
Mitochondrial DNA (mtDNA) was isolated from 8 different natural populations of the rodent species Otomys irroratus (Muridae: Otomyinae) and from one population of the species 0. angoniensis occurring in South Africa. MtDNA samples were cleaved with five different restriction endonucleases, end-labelled with phosphorous-32, separated by electrophoresis on horizontal 1 % agarose gels and the resulting fragment bands were detected by autoradiography. The individual-specific fragment banding patterns were analysed and compared among the various populations. The percent sequence divergence among and between the populations was calculated using the formula of Nei (1979). A matrix of sequence divergence values for all intergenomic pairwise comparisons was subjected to a clustering analysis by the unweighted pair group method with arithmetic means (UPGMA, Sneath and Sokal, 1973), using the computer programme NTSYS (Rohlf: 1988). The results of these analyses allowed for a preliminary identification of phenetic groupings in the data set. A matrix generated by scoring the restriction endonuclease fragments as present or absent was used to generate a phylogenetic dendogram using the BIOSYS (Swofford and Selander, 1989) programme. The overall restriction fragment variation uncovered in this study revealed 15 different mtDNA haplotypes within the 20 individuals examined. This corresponded to a high degree of polymorphism in the populations where more than one specimen was available, as well as within the species 0. irroratus. There were no clones that were shared between any of the populations sampled. The intrapopulation sequence divergence values uncovered in this study were high (range 0.35 % to 5.08 %), but also consistent with some other reports in the literature for intrapopulation variation. The outgroup, 0. angoniensis revealed the highest divergence values when compared to the mtDNA clones found in 0. irroratus. The phenetic and cladistic cluster diagrams revealed overall similarity with one another. There appeared to be little correlation between the topology of the mtDNA haplotype phenograms and the geographic distance of the sample localities. There was, however, a marked congruence between the distribution of mtDNA haplotypes and the distribution of three distinct cytotypes occurring over the species range. A possible polyphyletic evolution of populations of 0. irroratus was inferred from the cladistic analysis.
Monitoring the brown wattle mirid, Lygidolon Laevigatum (Hemiptera : Miridae)
(1995) Ingham, Deidre Suzanne.; Samways, Michael John.
No abstract available.
Use of space and activity rhythms of spotted-necked otters in the Natal Drakensberg.
(1995) Carranza, Ilaria d'Inzillo.; Perrin, Michael Richard.; Rowe-Rowe, David Treloar.
The study was carried out in Kamberg Nature Reserve (Natal Drakensberg) from June 1994 to August 1995. Seven spotted-necked otters were fitted with an intraperitoneal radio-implant; radio-tracking was performed by both temporally independent locations and 24h continuous tracking sessions. When active, otters were always found in aquatic habitats, mainly dams, the river or oxbow lakes. Dense vegetation cover, as trees, reeds, and tall grass were preferred while resting. Otters were active both during the day and during the night, with peaks of activity at twilight. The amount of time spent in consecutive activity varied seasonally together with the main prey items exploited. Average home range area was 11.3km², including a stretch of river with an average length of 14.8 km. No intersexual nor intrasexual territoriality was detected. Intraspecific relationships varied with the dispersion and availability of food resources.
The effects of forest fragmentation on bird species in Madagascar : a case study from Ambohitantely Forest Reserve on the central high plateau.
(1995) Langrand, Olivier.; Maclean, Gordon Lindsay.
Considering the high rate of endemism in Madagascan organisms, which are mostly restricted to forest ecosystems, and the accelerating rate of deforestation affecting the island, it is critical to understand the effects of forest fragmentation on Malagasy biota to allow for better management of species within ecosystems. Ecological and human-induced changes have led to the disappearance of forest from vast areas of the island, including on the central High Plateau. The Ambohitantely Special Reserve, located on the central High Plateau at 1500 m asl, was selected as the study site for research on the effects of forest fragmentation on forestependent bird species in Madagascar. The Ambohitantely special Reserve covers 5600 ha of which 50% are natural forest, 35% are anthropogenic grassland savannah and 15% are exotic plantations. The forest, described as East Malagasy moist montane forest, is 2737 ha in area, of which 1487 ha are comprised of 513 forest fragments scattered around the largest block totalling 1250 ha. To investigate the effects of forest fragmentation on forest-dependent bird species, seven forest fragments were selected, ranging from 0.64 ha to 136 ha, in addition to the largest block, referred to as the control site. The bird species composition and relative abundance in different-sized fragments were assessed in reference to the control site, by using a combination of two standardized sampling methods: mistnetting and point-counts. A total of 1804 mistnet-days were accrued, 1026 in the control site and 778 in the seven forest fragments, leading to the capture of 491 birds of 26 species. A total of 160 point-counts was made at 39 different sample plots totalling 53 h 29 min of censusing, and a record of 30 species. A total of 72 bird species including 54 breeding forest affinities of the avifauna of Ambohitantely were defined with reference to 32 forest sites scattered across Madagascar. The species composition in all fragments are fully nested subsets of the control site and the species distribution in the fragments does not represent random subsets of the control site. The analysis of the bird communities in different size fragments indicates that the occurrence of bird species reflects a regular pattern of species extinction in relation to decreasing size of forest fragment. Species composition is discussed in reference to Ambohitantely's long history of isolation that may have led to extirpation of bird species from this site. The higher bird taxa decrease in number or totally disappear as a result of their ecological specialization. Equally, they are the most affected by edge effects (e. g. Atelornis pittoides). The main ecological trends in disappearance or extinction of species is a decrease in the number of small-bodied insectivorous understorey species and mid- and upper-stratum small-bodied insectivorous and nectarivorous species. Insectivorous species are particularly affected by forest fragmentation and three forest-dependent species found in Ambohitantely Forest are particularly sensitive to forest fragmentation: Newtonia amphichroa, Calicalicus madagascariensis, and Cyanolanius madagascarinus. The biological (flora species composition and forest structure) and the physical (temperature, moisture, and light) changes generated by the fragmentation of the forest have a greater impact on highly specialized foraging guilds and this explains the pattern of current bird species composition in Ambohitantely Forest. The influence of forest fragmentation on the altitudinal migration process is debated and conservation measures such as the establishment of forest corridors are proposed to improve the protection of biota found in the Ambohitantely Special Reserve.

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