The physical and physiological condition of larval fishes throughout their development is believed to influence their survival, and ultimately to contribute to recruitment to the adult population. The study of larval condition is therefore central to larval fish ecology. / In this thesis I sought to (1) carry out an appraisal of the characteristics and the reliability of condition measures now being used, (2) assess the importance of maternal contribution to the nutritional status of larval fish, (3) evaluate the possibility that diel variability in metabolism could lead to serious biasing of the interpretation of condition measures obtained over time, and (4) assess the time course of the condition of larval fishes subjected to periods of intermittent feeding. / The experiments described in chapter 2 were designed (1) to assess the impact of female nutritional status on the quality of the eggs and larvae they produced, (2) to determine which of a series of nucleic acid and protein measurements were most responsive to post-hatching starvation, and (3) to determine whether the starvation dynamics of those measures was affected by female source. No significant correlation could be found between any of the maternal traits studied and eggs and larval measures. The results did show, however, that egg size was more variable between-clutches than within-clutch, was independent of embryonic developmental rate, but was positively related to larval size. / The existence and ontogeny of circadian (24 hrs.) and ultradian (<24 hrs.) oscillations in the nucleic acids and protein content of larval capelin was investigated in the laboratory experiments outlined in chapter 3. The most obvious long-terms trends occurred during the embryonic period when DNA and RNA content increased constantly, and during the post-yolk-sac period when RNA and protein decreased following sub-optimal feeding. / The objectives of the study described in chapter 4 were threefold, (1) to determine which of a series of nucleic acid and protein measurements were affected by intermittent (delayed-fed and delayed-starved) feeding conditions in capelin larvae, (2) to determine the dynamics and shape of the time response, and (3) to determine whether the empirical data gathered were consistent with models developed as a consequence of the review of the literature (chapter 1). Only the dry weight, and the quantity of DNA, RNA, and protein per dry weight differed significantly between starvation and ad libitum feeding controls. Starvation dynamics were less consistent with predictions. Of the indices investigated, the dynamics of the quantity of DNA and RNA per dry weight were the most consistent dynamics with model predictions. (Abstract shortened by UMI.)

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Waters from normal larvae of Aedes aegypti (L.) are highly attractive to ovipositing conspecific females, whereas waters from larvae infected with the entomopathogenic digenean parasite, Plagiorechis elegans Rudolphi, are rendered strongly repellent. The production of the repellent appears to be mediated by the degree of environmentally induced stress experienced by the larvae. Whereas waters from fully fed larvae were highly attractive as an oviposition site, these were rendered progressively less attractive, and eventually strongly repellent as the larvae were deprived of food over a period of 7 days. Crowding of the larvae elicited similar repellent effects as did close contact between larvae and the walls of the container in which they were reared. The site of infection in the tissues of the mosquito larvae also influenced the intensity of repellency. Thus, infections of the head and thorax induced the highest degree of repellency, and infections of the abdomen the lowest. The repellent effect overrode attraction and remained stable for more than one week at 27°C, and even longer at lower temperatures. Stressors which induced repellency all precipitated similar physical and physiological changes in mosquito larvae. They reduced wet and dry weights and the concentration of serum carbohydrates, amino acids, proteins and lipids. Both infection and crowding rendered larvae anorexic. As well, infected larvae appeared to be unable to convert trehalose to glucose, thereby exacerbating the energy deficit. Incubating infected larvae in a dilute glucose solution significantly reduced the repellent effect of their waters. Addition of glucose to already repellent waters had little effect. Larvae of another species, Aedes atropalpus Coquillett, were equally capable of producing repellent effects when infected with P. elegans, and gravid females of Ae. aegypti were equally sensitive to these as to conspecific waters. This sensitivity, however, was not reciprocal. Aedes

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Bibliography: leaves 278-288. / Microfiche. / xvii, 288 leaves, bound ill. (some col.), plates 29 cm

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The hymenopteran endoparasitoid, Cotesia rubecula, employs integrated forms of active and passive immune-suppression in overcoming the defences of its host, Pieris rapae, a cosmopolitan pest of cruciferous crops. The immune-suppressive activity arises from a complex of maternally secreted proteins and polydnavirus (PDV) particles, which are injected in a host larva with the parasitoid egg at oviposition. The PDV associated with C. rubecula (CrBV) is unusual in that only four main viral genes (CrV1-CrV4) are expressed in P. rapae tissues and that expression is transient, remaining at high levels only in the period between four and eight hours postparasitisation (hpp). Previously, CrV1 was characterised and found to inactivate host haemocytes by causing disruption of their cytoskeleton, leading to abrogation of immune-associated processes such as spreading. In this study, a cDNA library was constructed from parasitised P. rapae larvae and screened with total CrBV DNA, leading to isolation of CrV2 and CrV3. The open reading frame of each gene was cloned in a bacterial expression vector and the resultant recombinant proteins were used to produce antibodies against CrV2 and CrV3. CrV2 has an open reading frame of 960 bp (with no introns) and encodes a glycoprotein of = 40 kDa, which is secreted from infected haemocytes and fat body. Comparison of CrV2 deduced amino acid sequence with other known sequences revealed no significant homologies. CrV2 protein was detected in host larvae at 6 hpp, remaining in large amounts for at least a day and was declining by 48 hpp. A putative coiled-coil region at the C-terminus of CrV2 is suspected of involvement in formation of CrV2 trimers that were detected under non-denaturing conditions. CrV2 was visualised within haemocytes in large endosomes at 24 hpp. Although the function of CrV2 remains unclear, it appears to interact with host haemocytes presumably to suppress their immune function. The CrV3 gene contained and intron and was found to encode a C-type lectin (CTL) homologue, which is secreted from infected host haemocytes and fat body into haemolymph. Two CrV3 monomers (of = 14 and 17 kDa) were detected in parasitised larvae with the larger monomer being an N-glycosylated form of the smaller monomer. CrV3 dimers and tetramers were also detected in vivo. Recombinant CrV3 forms larger complexes and was shown to agglutinate ovine blood cells, an activity that was Mn²⁺- and Mg²⁺-dependent but was independent of Ca²⁺. CrV3-mediated hemagglutination was inhibited by EDTA but not biological concentrations of 29 potential ligands tested. Interestingly, CrV3 is similar to invertebrate CTLs associated with humoral defence but not with previously isolated viral lectins. Further, CrV3 homologues were recently detected in bracoviruses from C. ruficrus and C. karyai, indicating that a novel CTL family is expressed by some Cotesia-associated PDVs CrV3 probably interacts with a soluble host haemolymph component associated with host humoral immune defences. CrVl and Crp32 (an immune-suppressive C. rubecula calyx protein) were used to produce recombinant Autographa californica mutiple nucleopolyhedrosis viruses (AcMNPVs), pathogens with putatively enhanced virulence in P. rapae. Bioassays were undertaken to investigate the pathogencity of wild-type AcMNPV iu P. rapae (previously unreported) and the effect of insertion of Crp32. Although the proportion of larval deaths due to wild-type AcMNPV was significant, the slow rate of mortality indicated that P. rapae is only semi-permissive to AcMNPV. Crp32 insertion proved insignificant in terms of the proportion and rate of larval mortality. Given the semi-permissive nature of P. rapae, recombinant AcMNPVs expressing immune-suppressive and appropriate reporter genes may be useful for elucidating mechanisms of insect immunity and more specifically, how CrBV acts to subvert these mechanisms in P. rapae. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1109473 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / The hymenopteran endoparasitoid, Cotesia rubecula, employs integrated forms of active and passive immune-suppression in overcoming the defences of its host, Pieris rapae, a cosmopolitan pest of cruciferous crops. The immune-suppressive activity arises from a complex of maternally secreted proteins and polydnavirus (PDV) particles, which are injected in a host larva with the parasitoid egg at oviposition. The PDV associated with C. rubecula (CrBV) is unusual in that only four main viral genes (CrV1-CrV4) are expressed in P. rapae tissues and that expression is transient, remaining at high levels only in the period between four and eight hours postparasitisation (hpp). Previously, CrV1 was characterised and found to inactivate host haemocytes by causing disruption of their cytoskeleton, leading to abrogation of immune-associated processes such as spreading. In this study, a cDNA library was constructed from parasitised P. rapae larvae and screened with total CrBV DNA, leading to isolation of CrV2 and CrV3. The open reading frame of each gene was cloned in a bacterial expression vector and the resultant recombinant proteins were used to produce antibodies against CrV2 and CrV3. CrV2 has an open reading frame of 960 bp (with no introns) and encodes a glycoprotein of = 40 kDa, which is secreted from infected haemocytes and fat body. Comparison of CrV2 deduced amino acid sequence with other known sequences revealed no significant homologies. CrV2 protein was detected in host larvae at 6 hpp, remaining in large amounts for at least a day and was declining by 48 hpp. A putative coiled-coil region at the C-terminus of CrV2 is suspected of involvement in formation of CrV2 trimers that were detected under non-denaturing conditions. CrV2 was visualised within haemocytes in large endosomes at 24 hpp. Although the function of CrV2 remains unclear, it appears to interact with host haemocytes presumably to suppress their immune function. The CrV3 gene contained and intron and was found to encode a C-type lectin (CTL) homologue, which is secreted from infected host haemocytes and fat body into haemolymph. Two CrV3 monomers (of = 14 and 17 kDa) were detected in parasitised larvae with the larger monomer being an N-glycosylated form of the smaller monomer. CrV3 dimers and tetramers were also detected in vivo. Recombinant CrV3 forms larger complexes and was shown to agglutinate ovine blood cells, an activity that was Mn²⁺- and Mg²⁺-dependent but was independent of Ca²⁺. CrV3-mediated hemagglutination was inhibited by EDTA but not biological concentrations of 29 potential ligands tested. Interestingly, CrV3 is similar to invertebrate CTLs associated with humoral defence but not with previously isolated viral lectins. Further, CrV3 homologues were recently detected in bracoviruses from C. ruficrus and C. karyai, indicating that a novel CTL family is expressed by some Cotesia-associated PDVs CrV3 probably interacts with a soluble host haemolymph component associated with host humoral immune defences. CrVl and Crp32 (an immune-suppressive C. rubecula calyx protein) were used to produce recombinant Autographa californica mutiple nucleopolyhedrosis viruses (AcMNPVs), pathogens with putatively enhanced virulence in P. rapae. Bioassays were undertaken to investigate the pathogencity of wild-type AcMNPV iu P. rapae (previously unreported) and the effect of insertion of Crp32. Although the proportion of larval deaths due to wild-type AcMNPV was significant, the slow rate of mortality indicated that P. rapae is only semi-permissive to AcMNPV. Crp32 insertion proved insignificant in terms of the proportion and rate of larval mortality. Given the semi-permissive nature of P. rapae, recombinant AcMNPVs expressing immune-suppressive and appropriate reporter genes may be useful for elucidating mechanisms of insect immunity and more specifically, how CrBV acts to subvert these mechanisms in P. rapae. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1109473 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture and Wine, 2004