Zoology - Theses
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ItemNo Preview AvailableThe ecology and song of the duetting Eastern whipbird (Phosphodes olivaceus)(University of Melbourne, 2005)In this thesis I investigate the function of antiphonal duets, using as my model system the Australian eastern whipbird, Psophodes olivaceus. Fieldwork was carried out between 2000- 2003 on a colour-banded population of eastern whipbirds at Mimosa Rocks National Park, near Tathra, NSW. Eastern whipbirds form stable, long-term, socially monogamous pair bonds with a low rate of pair divorce. Males and females show sex role convergence in parental care and territory defence. While only females build the nest and incubate, both sexes feed offspring at the nest, with males feeding nestlings at a higher rate than females. On fledgling the brood of two is divided and each parent cares exclusively for one fledging during an extended period of post-fledging care. Males and females together defend an exclusive territory throughout the year. Competition for territories at this site is intense, due to a high rate of adult survival, limited dispersal by offspring and an extremely low rate of territory turnaround, despite the presence of numerous unpaired adult 'floaters'. Intra-sexual competition between females appears to be particularly strong given that sex ratios from nestling through to unpaired adult stages are female-biased. Eastern whipbird males and females coordinate their songs to form precise duets that are initiated exclusively by the male. Males and females each possess a repertoire of different song types, which are combined non-randomly to form specific duet types. Females produce two types of song: response songs, which are mainly used in the context of a duet, and 'type n' songs which are used only as solo songs. Both sexes share most of their songs with same-sex neighbours and the repertoire of song types appears to play an important role in allowing song type-matching during territorial interactions with intruders. Playback experiments suggest that the sexes differ in the extent to which they are influenced by the song types of rivals and partners during interactions. Males matched most of their songs with the song type broadcast by the speaker during simulated intrusion by male rivals. Females, in contrast, always fitted the song types of their partners rather than matching the songs of female rivals. By replying to their partner, females may be signalling their commitment to the pair bond, or demonstrating their own, or their partners, paired status to female rivals. Further playback experiments confirmed that females showed a more aggressive response to simulated intrusion by female rivals than male rivals, and answered a higher proportion of their partner's songs to form duets in the presence of a same-sex rival. Female eastern whipbirds therefore appear to reply to their partners in order to defend their exclusive position within the partnership. This behaviour appears to be the consequence of high intra-sexual competition between females for mates, coupled with high benefits associated with maintaining exclusive access to male care. The high level of intra-specific competition between females also seems to have led to the development of a novel vocal strategy in the eastern whipbird. Females not only replied to their partners but also to male intruders to form precise extra-pair duets which were similar in structure to pair duets. Simulated intrusions suggested that the rate of extra-pair duets produced was highest in the presence of a female rival. Thus, females may respond to males other than their partners as a means of type-matching and overlapping the songs of female rivals.
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ItemA molecular analysis of bryozoan dispersal(University of Melbourne, 2002)Cheilostome bryozoans disperse primarily via short-lived, non-feeding larvae. Shiphull fouling is the likely cause of recent introductions of some species. Patterns of genetic diversity of three invasive bryozoans were compared to determine the effects of modem range expansion on genetic structure. The influence of natural dispersal mechanisms and local geological factors was assessed in studies of the genetic variation of two bryozoans that occur naturally in south-eastern Australia. Mitochondrial COI gene sequences of 388-429 base pairs in length were compared for each species. In addition, an experiment was conducted to determine whether bryozoans and other organisms within a marina show different microscale recruitment responses in the presence of 'antifouling' paints used to prevent the settlement of marine organisms. The occurrence of high-tolerance responses in introduced populations could indicate effects of selection associated with hull-fouling. The three introduced species showed contrasting levels of mitochondrial nucleotide diversity. Bugula neritina occurred throughout temperate and tropical oceans at the time of first taxonomic records. Globally widespread sampling revealed a single cosmopolitan species with no detected COI nucleotide variation. This finding contrasts with previously reported COI evidence of multiple divergent cryptic species of B. neritina on the American coastline. Minimal sequence diversity was found in the introduced gene pool of Watersipora subtorquata, an Atlantic bryozoan that has recently colonised the Pacific (?30 = 0.0016). The genetic homogeneity suggests expansions of B. neritina and W. subtorquata originate from a single population source. Comparison of introduced populations of Watersipora arcuata, a bryozoan that has recently colonised Australia, Hawaii and other coastlines from an Eastern Pacific source, revealed comparatively high nucleotide diversity (?51 = 0.0221), suggesting range expansion originated from multiple ancestral isolates. Sequences demonstrated that the range of Bugula dentata, a species that occurs widely on tropical and subtropical reefs, consists of a complex of divergent species that formed during the Miocene. A shallow area of epicontinental shelf underlying the Bass Strait sea zone between Victoria and Tasmania has been periodically exposed as a result of Quaternary glacioeustatic fluctuation. Genetic diversity in south-eastern Australian marine species is potentially affected by isolation across the temporary land bridge and the pattern of interglacial recolonisation of Bass Strait. Populations of B. dentata, sampled at four areas in south-eastern Australia, had a shallow phylogeographic structure (?16= 0.003, Fst = 1.0), suggesting post-Pleistocene recolonisation from a single refuge zone. Mucropetraliella ellerii, a bryozoan that is endemic to the inner south-eastern Australian shelf, was shown to have high nucleotide diversity across its range (?53 =0.0724). Populations in southern and eastern Australia were separated by a net sequence divergence of 10.9% (K2P-corrected), suggesting a long-term (Miocene-Pliocene age) population break. Analysis of the demographic signal present within the sequence samples provided evidence of contrasting genetic effects related to recolonisation. Differences in sequence diversity of each of the two major M. ellerii isolates may be related to the area of continental shelf that houses refuge populations for recolonisation. In the marina experiment, a copper oxide and a Tributyltin (TBT)-based antifouling paint were used to create ion diffusions around settlement plates. Differences in the density of recruitment of different species among three treatments (control, copper and blank) were measured to test the hypothesis that introduced populations of shiphull fouling species have a higher chemical tolerance than non-introduced species. There was one substantive effect. Chemical treatments reduced densities of a native bryozoan Celloporaria nodulosa, whereas the introduced species Watersipora subtorquata showed a high tolerance of the effects of chemicals, increasing in density on plates surrounded by copper antifouling paint. The bryozoan fouling response thus exhibits species-level variance that is relevant to mechanisms of introduction and may prove to be a useful trait for studying how adaptation and population dynamics are linked.
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ItemEffects of transient copper pollution events on the ecology of marine epifaunal assemblages(University of Melbourne, 2001)Bays and estuaries are subject to anthropogenic toxic waste inputs from many sources and heavy metals are common constituents of that waste. Many toxicant inputs are discrete in time and patchy in space (e.g. spills, urban runoff and periodic discharges) and assemblages may be subject to repeated transient disturbances. I employed a field-dosing technique in many small-scale manipulative studies to assess the impacts of transient copper pollution events on hard-substrate marine invertebrate assemblages. I manipulated the timing, frequency and intensity of transient copper pollution events, factors which have been found to be important determinants of the impact of non-chemical disturbances. Short-term studies of the effect of copper pulses on the initial colonisation of hard substrates in temperate Port Philip Bay revealed direct negative toxicities of the chemical on the recruitment of invertebrates from many phyla including barnacles, serpulids and bryozoans. Field measurements of the copper dose demonstrated that impacts were correlated with the highest concentrations of copper. As concentrations rapidly diminished, many impacts were obscured by high juvenile mortalities or large settlement events. In sub-tropical Hong Kong, recruitment rates and growth were high, especially for the ubiquitous fouling serpulid Hydroides elegans. Within two weeks, this organism was limiting settlement of its own kind and copper pulse impacts were manifest as a shift downwards in the size of recruits close to the copper source. Recovery was also rapid in this assemblage and in both climates, transient pulses that occurred in the initial weeks of longer-term experiments had no lasting effects on assemblage composition. In longer term studies, pulse copper pollution events dramatically altered the assemblages at all sites and times causing a direct reduction in the densities of large space-occupying solitary ascidians. In response to this removal of the dominant ascidians, there were increases in recruitment of many different phyla, and in the abundance of older individuals of some serpulid and bryozoan taxa. In particular, organisms known to be good colonisers but poor competitors for space such as serpulid polychaetes, generally occurred in densities an order of magnitude higher on plates exposed to copper pulses. This was considered to be a density- mediated indirect effect of the toxicant. Experiments on the effects of copper pulses on serpulid densities in the absence of competition for space from other recruits, confirmed this interpretation. The impact of transient pollution events persisted for some time after the agent of disturbance was removed. For the most part, the effects of a single 2-day pulse copper pollution event on an established (8-week old) assemblage had a press effect on community structure that was still evident a further 8 weeks after it had occurred. If a pulse pollution event had a negative effect on an organism�s density, then increasing the intensity or the frequency of that pollution event accentuated that negative effect. If a pulse pollution event had a positive effect on an organism�s density then increasing the intensity or the frequency accentuated the positive effect.
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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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ItemThe effects of artificial watering points on the distribution and abundance of avifauna in an arid and semi-arid mallee environment( 2002)The role of artificial watering points in the avifaunal dynamics of the semi-arid mallee woodlands of southeast Australia was examined. Species richness and abundance were monitored throughout the year at different distances from water to determine how birds were distributed around water points and how this changed in relation to environmental factors such as climate. Vegetation attributes were also measured to determine which factors explained patterns in the avifauna with distance from water, and also to allow a description of the vegetation in relation to the water points. Water points were monitored throughout the year to determine which species were utilising them, under which environmental circumstances and for what purposes. Knowledge of the water utilisation behaviour of individual bird species allowed some explanation of their distribution patterns, as well as an ability to predict the likely effects of water point closure on those bird species. The closure of two water points during the study allowed an assessment of the immediate effects of water point closure on avifauna (For complete abstract open document)