The biology of Secculina carcini, a parasite on the common shore crab, Carcinus maenas, was studied with particular emphasis on larval morphology, biochemical content and energetic demands. The prevalence and distribution of the parasite was also investigated. The field studies carried out on the populations of S. carcini on C. maenas in northern France and North Wales, together with a review of the literature, demonstrated a disparate distribution. The larvae of S. carcini are lecithotrophic and can develop within 5 days to the cyprid and are capable of settlement 2 days later. The highest prevalence for the parasite was observed to correlate with semi-enclosed bodies of water. It is proposed that in this situation, with the short development time, the larvae are retained, thus increasing the probability of successful cypris settlement. Such coastal systems are susceptible to variable conditions, consequently experiments were undertaken to investigate the larval tolerance to temperature and salinity variations. A morphological study was carried out on the naupliar stages of S. carcinl. The typical cirripede limbs were simple and lacked gnathobases. There was also a vestigial ventral thoracic process present in the stage III and stage IV nauplius. These observations supported the argument that the rhizocephalan nauplius fits within the cirripede nauplius form. - ii - The energy budget study, involved the investigation of ash-free dry weights per larva, respirometry for each larval stage and analyses of the biochemical constituents using colorimetric and gravimetric techniques, Finally an equation was developed which demonstrates the energy budget for S. carcini, from the beginning of larval development to settlement on the host and the subsequent metamorphoses to the inoculation stages.

No description available.

Microorganisms are a goidmine for evolutionary genetics as their genomes can evolve at an extraordinary rate which results in some of the most extravagant adaptations in terms of genome structure and function as well as survival in the most unusual environments. One trend observed in several evolutionary scenarios is genome degeneration. It is most prominent in endosymbionts and obligate intracellular parasites and is a consequence of many constraints encountered in the intracellular environment. The process involves loss of many protein-coding genes, resulting in greater dependence on the host, and loss of non-coding DNA such as intergenic regions, which has a direct impact on regulation of genome function. I have chosen two evolutionarily distinct systems to analyze the stages and functional consequences of genome degeneration, namely the impact of genome compression on transcription in an obligate parasite Antonospora locustae (genus Microsporidia), and gene content in the mitochondrion of a diatom endosymbiont found in the dinoflagellate Durinskia baltica. I have successfully mapped transcriptional start and termination sites from 14 loci in Antonospora locustae, and cloned fragments of two genes that are part of the electron transport chain from the mitochondrion of the diatom endosymbiont in Durinskia baltica. My analysis reveals that transcription in A. locustae is always initiated immediately upstream of the open reading frame at a single point for every locus, whereas transcriptional termination can occur at several points for a single gene and, in some instances overlaps with a downstream reading frame. The identification ofNADH5 and ATPase9 from the mitochondrion of the endosymbiont in D. baltica is further evidence for the preservation of function in this enigmatic organelle. / Science, Faculty of / Botany, Department of / Graduate

The life-cycle of Rhipidocotyle campanula (Dujardin, 1845) has been experimentally demonstrated and the species identity confirmed. Sporocysts were recovered from digestive glands of the freshwater-mussel Anodonta anatina, and in heavily infected 'hosts from the reproductive, system. Both cercariae and glochidia are released simultaneously in mussels where the reproductive system is partly invaded by sporocyst tubules. The development of the cercariae in the sporocyst tubules has been studied briefly fusing histological and histochemical methods. The liberation of cercariae varied- between >1000/mussel/day to none, and is intermittent. Behaviour of the cercariae including swimming, response to light and gravity, survival and entry, into the secondary host, is described. The morphology of the cercaria has been studied in detail using electron microscopy, histochemistry and histological methods and its significance analysed in relation to free-living existence. This is the first attempt to study the cercaria of R. campanula in any detail. Cercariae enter the secondary host passively and encyst in the subcutaneous fatty tissue beneath the lining of the pharynx, and in some cases in the gill arches. This is the only species of bucephalids where cercariae enter the secondary host passively. Encysted metacercariae attain maximum development after 5-6 weeks and survive nearly 200 days, but spontaneous excystation takes place only in cysts 80-90 days old. Adult flukes were recovered from the posterior intestine and rectum of the perch (Perca fluviatilis) six weeks after feeding fully developed metacercariae. Spermatogenesis and oogenesis were studied in the adults until egg formation. Miracidial development could not be observed. External morphology using SEM of cercaria, metacercaria and adult has been studied and compared. This is the first report of SEM study of these stages of R. campanula. A brief review of the literature is given and the problems of systematics and taxonomy of the family Bucephalidae the taxonomic position of R. campanula are discussed.Tabular summaries are given for the previous life-cycle studies of bucephalids, synopses of bucephalid trematodes and all previous reports of bucephalid cercariae.

D.Sc. (Zoology) / Please refer to full text to view abstract

No description available.

No description available.

This study was undertaken to determine the parasite complex of the whitetail deer of British Columbia, the frequency of these parasites, and the factors influencing parasitism of these deer. An examination of 69 whitetail deer and 7 mule deer was made for the presence of ectoparasites and endoparasites. Autopsies were performed at various intervals from July 1964 to May 1966. The whitetail deer examined were host to 25 species of parasites including 3 species of lice, 2 species of ticks, 2 louse flies, one bot fly, 4 cestodes, 1 trematode and 11 nematodes. The maximum number of species infesting a single deer was 11. The average number of species per whitetail deer was 5.9. With the exception of the nose bot the frequency of infestation of all species was found to be light. The 7 mule deer examined were host to 22 species of parasites. The maximum in a single deer was 13 and the average number of species per deer was 10.6. Mule deer shared the same ectoparasites as whitetail deer, but harboured much heavier infections of intestinal nematodes and cestodes. Tne bot fly Cepnenemyia jellisoni, the liver fluke Fascioloides magna and larval lungworms were the only parasites found to have any appreciable effect on host tissues. The presence of large numbers of cattle and horses on whitetail winter ranges has not brought about heavy parasite infestations in whitetail deer. The parasitism of whitetail deer was very light in spite of overcrowding of deer, overbrowsed ranges, malnutrition and extremes of climate. / Science, Faculty of / Zoology, Department of / Graduate

This study was undertaken to determine the identity of Philonema oncorhynchi from anadromous sockeye and Philonema agubernaculum from non-anadromous trout, and also to test the hypothesis that the worm in salmon is dependent on hormonal stimulus from the host for synchronization of reproduction. On the basis of differences found in life cycles, cross infection and starch gel electrophoresis, P. oncorhynchi and P. agubernaculum are considered to be different species. The hypothesis was tested experimentally, using salmon pituitary extracts and synthetic stilbestrol. Pituitary extracts accelerated the production of larvae in the uterus, of the worm and stilbestrol inhibited the gonadal development of the fish, but had no apparent effect on the worms. The hypothesis was further supported by the results of transplantation of adult but non-larvigerous worms from maturing sockeye into immature trout. Larval development failed to take place in recipient hosts. As well, larvigerous worms were collected only from sexually mature fish, whether 3, 4 or 5 years old. Rapid development of the worm paralleled the rapid gonadal development of the fish during the last 6 months of the fish's life. Sexually immature sockeye had only immature worms. / Science, Faculty of / Zoology, Department of / Graduate

This study represents the first of its kind to evaluate the importance of spatial and temporal co= incidence between parasitic insects and their insect hosts. Extensive and intensive field observations here demonstrate that lack of coincidence is possible between the European pine sawfly, Neodiprion sertifer Geoff. and its three most important parasites. In the ichneumonids, Exenterus canadensis Prov., spatial coincidence is nearly perfect, while temporal coincidence may be poor. The bombyliid, Villa sinuosa (Wd.) shows imperfect spatial coincidence, but good temporal coincidence. In the ichneumonid Pleolophus basizonus (Grav.) both spatial and temporal coincidence may be imperfect. The degress of coincidence are related to the physiology of development and the behaviour of the parasites and their host in their variable environmental contexts. The interrelations of host density, parasite density, time of contacts, number of eggs laid, and number of hosts attacked, were studied experimentally with P. basizonus. The results were more closely described by the predictions of the Holling than of the Watt equation. The distribution of eggs in hosts was more often adequately described by the negative binomial than the Poisson equation for probabilities. The effect of asynchrony in the species studied cannot be considered without reference to superparasitisms. At low host densities superparasitism largely buffers effects of decreased synchrony, but its buffering diminishes to an asymptote as host density increases. In any given generation, imperfect spatial coincidence has little effect where attack is asymptotic. Simulations of host-parasite interactions over 25 to 35 host generations showed that for P. basizonus and E. Canadensis, host and parasite populations would become stable after passing through one or more oscillations even when, temporal and spatial coincidence are reduced. Predictions for V. sinuosa indicate its inability to restrain host populations even at perfect coincidence. / Science, Faculty of / Zoology, Department of / Graduate