Zoology - Theses
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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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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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ItemA comparative study of the flora and fauna of exotic pine plantations and adjacent, indigenous eucalypt forests in Gippsland, Victoria( 1978-01)The introduction and establishment of a new and markedly different environment within a long established natural system provides an excellent opportunity to study the principles of adaptation and colonisation by native species. In Australia, an example is furnished by the conversion of large areas of native eucalypt forests to mono-cultured plantations of Monterey Pine (Pinus radiata). The principal aim of this study was to assess which species of native mammals, birds and higher plants are able to utilise or occupy such plantations. Successional aspects of community structure, and colonisation in pine forest systems, were investigated by considering stands of different ages. A variety of adjacent native eucalypt forests provided controls and indicated the range of potential colonisers. Various habitats in both forest types were studied with regard to potential nest sites and availability of food, in order to determine those habitats most favourable for mammals and birds. The effect, on wildlife, of clearing eucalypt forests, but leaving forest remnants along gullies, was also assessed.
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ItemLife-history strategies of five species of intertidal limpet( 1977)The life-long strategies of five species of intertidal limpet, Cellana tramoserica, Notoacmea petterdi, Patella peroni, Patelloida alticostata, and Siphonaria diemenensis, which occur on the same shore but in different tidal zones, are considered in relation to their different environments. Attention is focused upon reproductive effort, which is defined as the percentage of assimilated energy devoted to reproduction, and which is measured for each species by using annual energy budgets. Environmental and demographic factors, which previous workers have suggested may have important influences on the level of reproductive effort, are investigated. In particular, interspecific differences in reproductive effort are compared with differences in the availability of food resources, differences in the magnitude of density-independent causes of mortality, differences in adult mortality rates and differences in extrinsic adult mortality rates (i.e. the adult mortality rates that would occur in the absence of expenditure of energy in reproduction.) The results of the present study indicate that reproductive effort is correlated with the availability of food resources, but that the primary determinant of the optimum level of reproductive effort is the rate of extrinsic adult mortality.
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ItemThe evolutionary significance of postmating isolation in anuran amphibians( 1974)Levels of intertaxon genetic incompatibility were determined within three south-eastern Australian amphibian species groups: the genus Ranidella; the Geocrinia laevis complex; and the Litoria ewingi complex. These groups include, wide-ranging taxa in which an assessment of regional differentiation could be made, as well as a variety of intertaxon interactions ranging from broad intergradation to extensive sympatry. Particular emphasis was placed on analysis of narrow zones of interaction between taxa in an attempt to determine the relative importance of the various types of reproductive isolating mechanisms outlined by Littlejohn (1969). The major method employed in these studies was in vitro artificial hybridization. Data derived from this investigation were combined with other available information on aspects of reproductive isolation and general biology of the included taxa, both to assess the significance of reproductive isolation, and to determine phylogenetic relationships and patterns of speciation within the three species groups. The wide-ranging taxa show a high level of genetic uniformity throughout their ranges, suggesting that levels of organization higher than local populations (i.e. biological species) exist in nature. The operation of two fundamentally different kinds of potential postmating isolating factors is suggested. Firstly, a significant level of intrinsic postmating isolation between species, where present, results in their effective and irreversible separation. However, it was found that cognate taxa were generally not characterized by high levels of genetic incompatibility. Secondly, ecological differences between interacting taxa, arising from adaptations to discontinuous, heterogeneous habitats, could provide significant isolation which, in terms of natural selection, has the same effect as intrinsic postmating factors. Premating isolating mechanisms are clearly highly adaptive in terms of reproductive efficiency and success. However the adaptive significance of premating isolation is manifest only in situations where selection acts against individuals which mismate. Hence isolation between interacting taxa dependent solely on premating isolating mechanisms is tenuous and likely to break down. It is proposed that future research on the mechanisms of divergent evolution should be directed more towards detailed studies of extensively sympatric cognate species, particularly their ecological interactions, and less towards the genetic aspects of hybrid zones.
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ItemThe evolution and ecology of the Gadopsis marmoratus complex( 1986)The Family Gadopsidae is the only family of fishes in South-eastern Australia which is both endemic to this region, and strictly confined to fresh water. Although several species of Gadopsis have been proposed, prior to the commencement of this study only one species, G. marmoratus Richardson, was formally recognised. This species was known to exhibit considerable geographic variation in morphology, colouration patterns, and size; and it had been suggested that the taxonomy of the genus was in need of review. This study is an attempt to: (i) determine the number of species in the, G. marmoratus complex; (ii) assess the relationships between G. marmoratus and any additional taxa in the complex; (iii) Formulate a biogeographic hypothesis to account for the geographic distributions and phylogenetic relationships of the taxa in the G. marmoratus complex; and, (iv) examine ecological characteristics of a population of Gadopsis from each side of the Great Dividing Range in Victoria. Analysis of meristic variation revealed that two sympatric taxa of Gadopsis were present in north-eastern Victoria. No evidence of hybridization between these taxa was found. The two taxa have different numbers of spines in the dorsal fin, and the specific status of the taxon with only two spines in the fin was recognised by the formal description of G. bispinosus Sanger. By adoption of an evolutionary species concept, and using univariate and multivariate statistical analyses of meristic variation, it was shown that G. marmoratus was comprised of two divergent taxa. It was proposed that these taxa be recognised as separate species, and for the purposes of this study are referred to as northern G. marmoratus and southern G. marmoratus. Multivariate statistical analyses of morphometric variation supported the proposal to recognise northern G. marmoratus and southern G. marmoratus as separate species. Electrophoretic analysis of protein variation also supported the recognition of northern G. marmoratus and southern G. marmoratus, and confirmed that hybridization was not occurring between G. bispinosus and northern G. marmoratus. The level of genetic divergence between northern G. marmoratus and southern G. marmoratus was less than that between both of these taxa and G. bispinosus. This result was interpreted to indicate a close phylogenetic relationship between northern G. marmoratus and southern G. marmoratus, and supported the relationships suggested by the phenetic analysis of meristic and morphometric variation. A biogeographic hypothesis to explain the geographic distributions and phylogenetic relationships of the three taxa was proposed. The ancestry of the Family Gadopsidae has been the subject of some dispute, and the alternative views on this subject were critically reviewed. Support was found for a basal percoid relationship for the family, and this result suggested that Gadopsis may have been of Gondwanan origin. The freshwater life-cycle of all the members of the family was interpreted as further support for a freshwater origin for Gadopsis. Several ecological characteristics of a population of G. bispinosus from the King Parrot Creek and G. marmoratus from the Yarra River system were compared. Gadopsis bispinosus in the King Parrot Creek is a small, lightly-built, short-lived species compared to G. marmoratus from the Yarra River system. The two species were found to have similar reproductive biologies. The discovery of additional species of Gadopsis has created the need for further examination of the evolution and ecology of the G. marmoratus complex, and suggestions for such further study are included at the end of this study.