Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Michael Chapman, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 15, 2005). Document formatted into pages; contains vi, 76 pages. Includes bibliographical references.

Previous studies in the population genetics of the oyster drill Thais clavigera show that snails from the west coast of Taiwan belong to the same population. However, the genotype frequency of arginine kinase (Ark) in large snails is different among sites in the west coast. In general, changes of temperature and desiccation caused by tidal cycle are the most important twp environmental factors affect genetic variation of intertidal organisms. In the present study, the relationship between the frequency of Ark genotype and tide was evaluated through the following experiments. It has been found that the frequencies of Ark genotype of snails, collected in August with the size range of 25-35mm, were correlated to tides. A higher grequency of Ark63/100 (0.47~0.56) was in the upper intertidal and a higher frequency of Ark63/63 (0.49~0.66) was at the lower end. Moreover, the genotype frequency also varied with size, i.e. more Ark63/63 in small snails (<25mm) and more Ark63/100 in large snails (>35mm). Laboratory desiccative experiments indicated that snails with genotype of Ark63/100 preferred in the areas of high water level and Ark63/63 in areas of low water level. The laboratory results were consistent with the field data. To compare the enzyme activity, there was no difference among the genotypes of Ark63/63, Ark63/100 and Ark100/100at temperatures of 18, 24 and 30¢J. In summary, the frequencies of Ark genotype varied with tide and size and factors such as temperature, desiccation and reproduction may play important roles in the relationship.

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The variation of Arginine kinase (Ark) genotype frequency among populations of Thais clavigera has been reported in previous study. However, the difference which is originated from self-seeding or differential selection after recruitment is not understood. To answer this question, the spatial (i.e. Shainsan, Taisi, Budai, and Chiku) and temporal (sell length: <15mm, 15-20mm, 20-30mm, 30-40mm, and >40mm; year: 2001 and 2003) variations of Ark allozyme were examined by starch gel electrophoresis. There was no significant difference in the ratio of Ark genotypes (ark63/63, ark63/100, ark100/100) in the size range of <15mm among Shainsan, Taisi and Chiku. The result indicated that the populations of T. clavigera is from the same recruitment. In the size range of 15-20mm, the frequency of ark63/63 increased from southern to northern populations, i.e. 0.21(Chiku) < 0.33(Budai) < 0.60(Taisi) < 0.66(Shainsan), respectively. It is proposed that the variation of Ark genotypes among populations is resulting from stress of temperature or dessication. A significant difference in the ratio of Ark genotypes was found in the population of Taisi with the size range of 30-40mm. Besides, the frequency of Ark genotypes among populations was not related to the degree of imposex.