Zoology - Theses
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ItemThe effects of copper antifouling paints and marinas on the ecology of marine sessile epifaunal assemblages(University of Melbourne, 2000)An experimental field study was undertaken to evaluate the effects of copper dosed from antifouling paints on the development of sessile epifaunal fouling assemblages in southeastern Australia. The study system was chosen because of the importance of copper pollution in the marine environment and the fact that members of assemblages of this type are the target organisms of antifouling compounds. Experiments were conducted inside and outside of enclosed marinas, as it was hypothesised that the conditions found inside marinas may have led to differential effects of copper dose in this environment. Initially, I developed a system to dose copper to settlement plates in the field. After several pilot experiments, I chose a system that used a laboratory-made antifouling compound painted onto a collar around a settlement plate as the dosing method. Field tests established that this system exerted biological effects over the settlement plates, and that these effects lasted for at least four weeks. Field-measurement at four sites, of copper doses delivered to plates demonstrated that dose differed among sites and times of year. The difference appeared to be in part related to the amount of water movement. A field-study that compared fouling assemblages developing in two marinas near Melbourne, Victoria to assemblages at each of three nearby control sites, confirmed that the marinas affected assemblage structure. For each marina, a number of species showed an effect, but very few species showed the same effects across both marinas. After aggregation of the species to functional groups, some effects were found across both marinas. Three approaches were undertaken to investigate the effects of dosed copper and the marinas on establishment of sessile epifaunal assemblages. The first experiment examined early recruitment of assemblages and found that copper dose affected a number of species recruiting to the plates. Recruitment varied widely with time and between sites inside and outside the marinas, but the results seemed to reflect normal temporal and spatial heterogeneity characteristic of the recruitment of fouling organisms. The second approach examined growth rates and competitive abilities of colonial fouling organisms. By using clonal replicates of colonies, I was able to show that the populations studied showed heterogeneity in growth rates, and occasionally showed heterogeneity in the effects of treatments on growth rates. Partially as a result of this variability, significant treatment effects on growth rates were rare. I did not find any effects of dose or marinas on the competitive ability of colonies, but the number of experiments that examined this feature was very low. Finally, a longer-term experiment that utilised reciprocal transplants of plates between sites and doses showed that effects of the marinas on assemblages were more important than effects of dose. Once again, some results indicated that some species showed variability in the degree to which different populations were affected by treatments. Overall, I found that locations (inside or outside the marina) had a greater effect on determining the assemblage structure than did dosed copper, despite these dosing levels being well above background levels of copper in these marinas. This is probably due to a large number of factors associated with marinas over and above increased background heavy metal pollution. Several taxa appeared to show adaptation to local conditions or copper doses, and some appeared to show either heterogeneity in response to dosing or an ability to acclimate to dose. These types of findings have important implications for the manner in which we apply the findings of traditional laboratory-based ecotoxicology experiments to environmental management.
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ItemParental behaviour and mating system of the fairy martin, Hirundo Ariel(University of Melbourne, 1997)The birds are unique among the major animal taxa in that biparental care is common, occurring in about 90% of the 9000 or so extant species. Among these biparental species there is dramatic variation, both across and within taxa, in the extent to which males and females contribute to incubation and nestling care. However, despite considerable interest, the causes of this variation generally remain poorly understood. The aim of this thesis was to examine a range of factors that may contribute to variation in the participation of males and females within a population of the socially monogamous fairy martin, Hirundo ariel. Fairy martins are endemic to Australia and nest colonially in aggregations of enclosed mud nests. The sexes are morphologically similar, although only the female acquires a brood patch during the breeding season. In the Yarra Valley, where this study was conducted, colonies ranged in size from 8 to 29 nests. Over the three years from 1993 to 1996, birds arrived in the study area in September and usually commenced laying in October, although nesting activities were generally asynchronous both between and within colonies. Most colonies contained active nests until February. An average of at least 16% of adults and 5% of fledglings returned to the study area in the following year. Returning adults generally nested at the same colony site as the previous year (68%), while most first year birds nested at sites other than their natal colony (75%). Adult males were more likely to return than adult females. Similarly, fledgling males were more likely to return than fledgling females (assuming an equal sex ratio at fledging). Both sexes participated in building the mud nest, incubating the clutch and feeding the nestlings. Clutch size ranged from two to five (mean = 3.5) and declined during the course of the season. The clutch was attended for an average of 88% of the time during daylight hours, although attendance generally declined during the course of the day. Females were more attentive of the clutch than males (56%), resulting primarily from longer incubation bouts, but also shorter recess periods. Females almost invariably attended the clutch overnight, and were usually accompanied by the male. Total clutch attendance did not vary with clutch size, however, male attendance increased with clutch size while female attendance decreased. Total attendance increased with clutch age resulting from an increase in female but not male attentiveness. Both sexes were more attentive of the clutch on cooler days, especially in the early morning and late afternoon. The duration of the incubation period varied from 12 to 18 days (mean = 13.7), and was shorter if the clutch was attended for a greater proportion of the day. A mean of 1.8 chicks fledged per completed clutch, while 60% of these clutches produced at least one chick. The period from hatching to fledging varied from 17 to 32 days (mean = 22.1), and was longer for larger broods. Fledging success was highest during the middle of the breeding season (December). Adverse weather conditions, resulting in clutch and brood abandonment, were the most common cause of nest failure, and on several occasions also resulted in adult mortality. Pairs produced from zero to eight fledglings per season (mean = 2.8), with those that commenced nesting earlier in the season having higher annual productivity. Parents visited larger broods more frequently, although the visit rate per chick declined with brood size. Visit rate generally increased with brood age, reaching a plateau between days 8 and 16, before declining until the chicks fledged. The relative contribution of the sexes did not vary with brood size or brood age. Brood visit rate generally increased with ambient temperature and decreased during periods of rainfall. Male participation in incubation (both absolute and relative to his mate) declined with an increase in the proportion of fertile females in the colony. Males were most 'responsive' to the availability of fertile females in the early morning, when copulations are likely to occur most frequently. Furthermore, the decline in male contribution with the proportion of fertile females was greater among males with smaller than average clutches. Male contribution to brood visits also tended to decline with an increase in the proportion of fertile females over the most demanding days of the nestling period. These patterns, each demonstrated for the first time, provide strong support for the presence of a reproductive trade-off for males between parental and extra-pair copulation effort. This trade-off may be widespread among the 90% of bird species where males contribute to parental care. Microsatellite parentage analysis revealed that 14% (29/207) of young were not sired by the putative father, while 2% (4/207) appeared to be the result of conspecific brood parasitism. The frequency of extra-pair fertilizations was not influenced by nesting synchrony, but tended to increase with colony size. The genetic fathers of extra-pair young had larger tarsi, greater previous breeding experience, and were more attentive to their own clutch than both the male that they cuckolded and the other males in the colony. Moreover, males with previous breeding experience had greater paternity of their own brood than those without. These results are consistent with female extra-pair mate choice for 'good genes'. Male incubation attendance, both across and matched for bird, was lower for clutches with reduced paternity. Furthermore, males with reduced paternity took longer in returning to their clutch after a disturbance than males with complete paternity. Together, these results suggested that males may adjust their level of parental investment in relation to their confidence of paternity. However, these results were confounded by the relationship between male contribution to incubation and the availability of fertile females in the colony. Mean nestling mass was lower in broods with reduced paternity however there was no evidence that this resulted from a reduced rate of feeding by cuckolded males. Among the Hirundinidae, and birds in general, species with male incubation are usually sexually monomorphic and have relatively low frequencies of extra-pair paternity. This study indicates that the biparental fairy martin conforms to this pattern. The evolution/ maintenance of male incubation in fairy martins may, in part, relate to the small body size and high nesting density of this species.
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ItemMale germ cell transplantation(University of Melbourne, 1995)This thesis has explored the success of male germ cell transplantation in rats. Busulfan-treated black and white Long Evans rats were used as the germ cell-recipients, and white Sprague Dawley fetal and neonatal rats were used to provide donor germ cells which were transplanted by 2 different routes. Adult Long Evans male rats were injected intraperitoneally once or twice with busulfan, an alkylating agent, at a dose of 10 mg/kg body weight. Forty four days after the first busulfan treatment, their testes were essentially devoid of spermatogenic cells and therefore suitable as germ cell recipients. Following exposure to busulfan during intrauterine life on which primordial germ cells (PGCs) were exclusively destroyed, the rats at days 4 - 5 of age were devoid of germ cells and therefore used as newborn recipients. Donor fetal and newborn testes were excised and dissociated by trypsin-EDTA (fetal tissues) or collagenase/trypsin-EDTA (neonatal tissues) treatment. PGCs and gonocytes were purified by equilibrium centrifugation on a discontinuous Percoll gradient column. Alkaline phosphatase activity was used as a marker for both PGCs and gonocytes. Trypan blue exclusion was used to determine cellular viability. The donor germ cells were injected into the testes of the anaesthetised recipients by retrograde injection into the rete testis, or random multiple testicular injections. A total of 74 recipient rats were transplanted with either primordial germ cells or gonocytes. Forty eight of them were paternity tested with 563 fertile Sprague Dawley females, and they produced 2,280 progeny. However, none of the progeny was derived from the donor germ cells, as judged by coat colour. However, a detailed histological analysis of the recipient testes showed that the donor germ cells had apparently differentiated into mini-tubules or irregular segments of seminiferous epithelium within the lumen of the host�s seminiferous tubules, and exhibited qualitatively normal spermatogenesis in 13 out of 19 animals following rete testis injections. The stage of spermatogenesis of the donor intraluminal seminiferous epithelium was closely synchronised with that of the host�s epithelium, suggesting that the spermatogenic cycle is regulated locally by the intraluminal microenvironment. None of 15 neonatal or adult recipients given random multiple intratesticular injections showed any evidence of intraluminal spermatogenesis, suggesting that the donor germ cells were unable to migrate through the basement membrane of the host seminiferous tubules. In summary, this thesis has demonstrated that it is possible to transplant purified PGCs and gonocytes from one rat to another. Male germ cell transplantation therefore provides an interesting new tool for investigating the control of spermatogenesis, and if the success rate of the procedure can be improved, so that the donated germ cells all integrated with the host�s Sertoli cells, it could become an invaluable technique for manipulating the male germ cell line.
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ItemAn electrophysiological study of muscle in tissue culture(University of Melbourne, 1975)
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ItemThe endocrine control of reproduction in the harlequin bug, dindymus versicolour (herr.-sch) (hemiptera : pyrrhocoridae)(University of Melbourne, 1972)The work presented in this thesis is an attempt to provide further insight into the endocrine factors which initiate and control the development of eggs in the female insect. It was therefore imperative that part of this study was directed towards an understanding of the neuro-endocrine system of the insect studied. One characteristic feature of the reproductive cycle of Dindymus is the prolonged and continuous copulation. Copulation is essential for the initiation of the vitellogenic cycle; interruption of copulation results in a retardation or cessation of vitellogenesis. Consequently, special attention was given to the manner in which copulation influenced the endocrine system.
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ItemEmbryonic diapause in the field cricket Teleogryllus Commodus(University of Melbourne, 1972)The mechanism of control of embryonic diapause in Teleogryllus commodus was investigated by experiments aimed firstly at studying the parental role in diapause determination and secondly, at analysing some of the biochemical changes associated with diapause initiation and termination in the egg. Implantation procedures were used to investigate the possibility that maternal endocrine effects, of the type demonstrated in the silkworm Bombyx mori, operate in Teleogryllus. Endocrine organs were transferred from diapausing T. commodus adult females to adult females of the non-diapausing T.oceanicus species. The organs implanted included the suboesophageal ganglion, brain, corpus cardiacum and corpora allata. The T. oceanicus females were mated with both T. oceanicus and T. commodus males, and the diapause characteristics of the eggs were assessed. The implants were shown to have no positive effect on diapause in the egg. However the experiments did reveal that the T. oceanicus ? x T. commodus ? hybrid has an embryonic diapause. This was contrary to the results of previous hybridization studies with these two species. It was in fact considered generally that diapause is absent in hybrids between diapausing and non-diapausing crickets. The presence of diapause in the T. oceanicus ? x T. commodus ? hybrid was confirmed in an experiment which compared the respiratory rates and morphological development of the hybrid and parent species. A genetical model proposed to fit this result has suggested that diapause in Teleogryllus is controlled by both a cytoplasmic factor produced by the parent female and by factors determined by the embryonic genome. Biochemical investigations were aimed at elucidating the nature of these factors. It was shown that rises in the level of free amino acids associated with proteolytic activity occur at diapause initiation and during diapause development in T. commodus. The rise at diapause initiation was shown to precede water absorption and is likely to be associated with this activity. The occurrence of proteolysis during diapause development would seem to be of significance to the process of diapause termination. Diapause development was shown to involve changes in the acrylamide patterns of soluble proteins and a 20% reduction in the amount of lipoprotein. It was shown to be accompanied by an increase in the in vitro activity of a phenoloxidase enzyme. The activity was dependent on the pH, molarity and lipoprotein concentration of the homogenate. No role for this enzyme in the process of diapause termination could be suggested. A proposal for a biochemical mechanism of diapause is made. It is suggested that diapause is initiated by the inactivation of an enzyme or enzymes essential for embryonic growth beyond the diapause stage. Diapause development is then considered as a process of activation of this enzyme (enzymes) either by the removal of an inhibitor or the production of an activator.
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ItemNo Preview AvailableStudies in population genetics(University of Melbourne, 1959)Population genetics and. population dynamics have formed two distinct avenues of approach to a field of study which has become increasingly important over the last thirty years. Each has proved highly susceptible to mathematical analysis and to quantitative, rather than merely descriptive, treatment. It is, however, surprising to find that relatively little has been done to unite these two aspects of population biology, while in each theoretical work has tended to outstrip the small foundation provided by the observations so far recorded in the literature. Thus Birch (1957.P.217) was led to say... "I am quite sceptical of the predictive value of such mathematical models as have to date been proposed for natural populations". More serious still is the fact that the attempt to fit slender experimental data to such models has often blinded the experimenter to the possibility that factors of importance other than those considered in his model may contribute to the observed properties of the population. In particular, there has been little attention given to the genetic control of the form and rate of population growth; the work of Buzzati-Traverso (1955) was the first major experimental analysis to produce useful results along these lines. Much of the work on Drosophila populations has been done on small breeding groups which have been assumed to have reached an equilibrium density, although it seems likely that laboratory populations of Drosophila develop in the same way as those of Lucilia (Nicholson, 1954 and earlier papers), in which the population number fluctuates quite widely about a mean, not absolute, "equilibrium" level. Further, the number of individuals in the populations has not usually been determined with accuracy, so that it has seldom been possible to study small changes in population size. Preoccupation with "competition" experiments involving oligogenic markers has led even experienced workers to ignore the importance of modifying influences, particularly polygenic systems, associated with the genetic background. In this connection Buzzati-Traverso (loc.cit.) stated: "The fact is that the change in frequency of a single gene (or chromosome) during a number of generations means that the individuals carrying its allele will produce more or fewer adult offspring in the next generation than the individuals not carrying it. The factor which is decisive for changing frequency is a "productivity differential" involving of necessity the whole genotype and not one gene alone, for the latter will have different survival values in different genetic milies. Some extreme mutants, like those mostly used in laboratory experiments, may affect specifically the productivity of its carriers to such an extent as to make the effects of the rest of the genotype and of interactions of the mutant with it insignificant. But under natural conditions the commonest ease is very likely that of 'small* mutants where the natural selection mechanism probably involves many genes at one time" Even in the case of 'extreme' mutants erroneous or unsupported conclusions have been published (see later discussion of the relative adaptive values of the alleles at the white locus of Drosophila given by Merrell & Underhill, 1956); while in other instances over-emphasis of one particular factor has often prevented a balanced statement of the factors operating in laboratory population experiments. The discovery of selective mating in Drosophila, for example, resulted in the application of mating test results to population cage results without regard to other factors which might be causing the observed gene frequency changes. The work of Nicoletti & Solima (1956) and Morpurgo & Nicoletti (1956), amongst others, has passed largely unnoticed, although these authors adduced considerable evidence to support their view that selective mating is in fact not a controlling factor in laboratory cage competitions even where it can be demonstrated to occur in mating tests of the genotypes involved. In the same way, a sharp distinction has not always been made between the overall adaptive value of a genotype in a particular environment. The differential migration rates reported by liar land & Jackson (1958) under the title �Advantage of the white eye mutant of Drosophila melanogaster over the wild type in an artificial environment" provides an instance of such confusion. The only real measure of "advantage" or "superiority" is the relative contribution of a genotype to the gene pool of the succeeding generation, but these authors mention no breeding experiments at all. It is, however, clear that they have identified one of the factors which might be of importance in determining the frequency of white relative to that of its wild type allele in populations maintained in a particular environment. The main object of the present work has been to investigate further the relation of the genetic structure of a population to its rate and type of growth. Some attention has been given to problems of the sex-ratio and to change in gene frequency; in each case the underlying mechanisms have been studied. Emphasis throughout has been placed on the determination of the relative importance of the possible component factors under conditions of intense competition such as those found in population cage experiments.
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ItemPopulation dynamics of Australasian gannets (Morus serrator) breeding in Port Phillip Bay, Victoria; competition with fisheries and the potential use of seabirds in managing marine resources( 2000)Increasing exploitation of pelagic fish populations worldwide has often resulted in overfishing and the collapse of commercial fisheries and associated serious declines in many marine predator populations, including seabirds. These events highlight the competing demands for limited marine resources. Recent emphasis for the ecologically sustainable management of commercial fisheries has stimulated attempts to manage fisheries by incorporating knowledge of trophic interactions and ecosystem functioning, known as ecosystem-based fisheries management. Seabirds are often highly visible, wide-ranging upper trophic level consumers that aggregate in areas of increased ocean productivity and therefore be used as natural monitors of marine environmental conditions. Further, many seabirds commonly fed on commercially-exploited fish stocks (often targeting prey of similar size). In this study, the population dynamics of Australasian gannets (Morus serrator) breeding in Port Phillip Bay, Victoria, is investigated and competition between gannets and commercial fisheries is determined. In addition, the potential use of seabird reproductive and population parameters as indicators of the abundance of commercially exploited fish stocks, and pelagic conditions generally, is assessed.
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ItemThe role of Customary Marine Tenure and local knowledge in fishery management at West Nggela, Solomon Islands( 1998-04)A proper understanding of the management of small-scale subsistence and artisanal fisheries requires not only detailed sociocultural study, but comprehensive analysis of the state of the fished population(s) using rigorous stock assessment and other fisheries biology tools. This study comprises such an interdisciplinary approach taken in an attempt to understand subsistence and artisanal fishing at West Nggela, with a particular focus on the management of the artisanal trochus fishery. The importance of an understanding of Customary Marine Tenure is dealt with in some detail. An analysis of the various categories of fishers’ ecological knowledge about marine fauna, with an emphasis on trochus, is also presented, and discussed with respect to the categories of biological and ecological information considered by most fisheries biologists as essential to the assessment and management of a fishery. The theoretical basis of my approach to the study of local knowledge, which could broadly be termed “rationalist”, is discussed and defended against “postmodernist” criticisms. Trochus are currently overfished at most of the reefs I studied at West Nggela. Densities measured using mark-recapture were apparently low compared to well-managed fisheries elsewhere in the Pacific. The current market demand, and the ease of capture, storage and marketing of the product, indicate that pressure on the fishery (which includes some poaching) is likely to remain high, and some improvement in management is required. Egg-per-recruit and yield-per-recruit modeling indicates that enforcement of a minimum size limit of 8cm basal diameter would bring about immediate improvement in yields and recruitment in the fishery. Such a measure would not only be practical and expedient but also more culturally sensitive than many of the alternatives. The system of customary marine tenure at West Nggela, which includes a system of serial prohibitions on harvesting, appears not to be adapted to the high levels of pressure currently being exerted on this valuable species. An analysis of the property tenure system at Nggela, including two case studies of formal disputes, outlines some of the reasons for this problem. Local ecological knowledge about marine fauna in general, and trochus in particular, appears to mostly concur with, and in some cases extend, scientific knowledge. However, there appear to be subject areas in which local knowledge is lacking, and these typically include parameters related to yield and recruitment, such as growth, natural mortality, lifespan and reproductive ecology. In particular, for broadcastspawning species such as trochus, the relationship between dwindling stock densities and recruitment failure is usually not recognised by most fishers at West Nggela. Customary manne tenure and local ecological knowledge thus appear to be insufficient for maximising and sustaining yields of trochus at current levels of fishing pressure. Nevertheless, any new management measures, or fisheries developments, should remain sensitive to the dynamic and competitive nature of the property tenure system. Collaboration between fishery biologists and local fishers is recommended wherever possible. Efforts by fishery biologists to extend, to rural fishers, their knowledge of reproductive biology and ecology of broadcast spawning organisms are encouraged. Outside knowledge is likely to be embraced by fishers only if it is communicated in a way that is compatible with the cognitive framework in which most local knowledge is situated. Such an input of expertise, when combined synergistically with the extensive local knowledge of rural fishers, cannot fail to result in improvements to strategies for community-based fishery management.
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ItemThe impact of kangaroo grazing on sediment and nutrient mobilisation( 2000-05)The adverse impacts on vegetation and soils due to livestock grazing have been extensively studied for many years. The extent to which native wildlife may also be causing change to their environment, as a result of local increases in population density, has been the subject of debate in a number of countries. In Australia there has been a growing awareness in recent years that native herbivores, particularly kangaroos and wallabies, may also be causing changes to ecosystem dynamics. Environmmental changes, produced firstly by the aboriginal people and then by Europeans, have favoured the larger macropods, resulting in increased population levels. These impacts can also be seen in areas around cities, where pressure from urbanisation has restricted populations to smaller and smaller patches of remnant vegetation and reserves, increasing the pressure on diminishing food resources within these patches. This study focuses on one of the areas that supplies drinking water to Melbourne, the Yan Yean Reservoir catchment, which is situated 37 km north east of Melbourne. This study adds to our understanding of the impacts of native wildlife populations by investigating the extent of some of these possible changes to ecosystem dynamics.