Seasonality and simulation modeling of larval trematodes in freshwater gastropods : the potential role of interspecific interactions in parasite communities /
Research was conducted to shed light on the characteristics of an intermediate host population of snail, such as host seasonal population density, host size and population growth rate, that are responsible for the observed patterns of parasite species occurrences and distributions. A simulation mode...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731981361&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Research was conducted to shed light on the characteristics of an intermediate host population of snail, such as host seasonal population density, host size and population growth rate, that are responsible for the observed patterns of parasite species occurrences and distributions. A simulation model of parasite prevalence in a snail species was developed in order to determine the potential role of parasite interactions in shaping the structure of parasite communities in intermediate hosts. Gastropods were collected every other week from March 1, 1997 to December 20, 1998. The population of Physella gyrina indicated two peaks in abundance, one in March and a larger one in July. The population of Gyraulus parvus indicated two peaks in abundance, one in March and another in August. The population of Planorbella trivolvis indicated two peaks in abundance, one in March and another in June. Physella gyring was found to harbor five types of cercariae (amphistome cercaria A, xiphidiocercaria A and B, cercaria mutabile and a furcocercous cercaria). Planorbella trivolvis was found to harbor four types of cercariae (amphistome cercaria B and xiphidiocercaria C, D and E). Xiphidiocercaria A and B and the furcocercous cercaria showed a distinct seasonal periodicity. Amphistome cercaria A and cercaria mutabile did not show a distinct seasonality. A simulation model of the frequency of infection of Physella gyring with each cercaria type was developed and accurately predicted the seasonal frequency of infections. The model proved to be especially accurate in predicting the frequency of xiphidiocercaria A and B. This accuracy is a result of the fact that the model is based on a previous model designed for a parasite that utilizes a xiphidiocercaria. Results show that a model developed for one parasite species may prove to be equally accurate for other species with similar life cycles. Each of the eve individual models was integrated into a single model of the parasite community of Physella gyrina. The integrated model proved to be equally accurate in predicting the seasonal frequency of cercariae as the individual models. Results indicate that the presence of one parasite species has no effect on the presence or absence of others. There is no significant interaction among the parasite species infecting Physella gyrina. Because the efficiency of transmission of infective stages of trematodes is low, the host resource is never in short enough supply to be significantly affected by competition. |
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| Item Description: | Vita. "Major Subject: Wildlife and Fisheries Sciences". |
| Physical Description: | xiii, 176 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 164-175). |