Coral reef is one of the prominent habitats in Taiwan where sea slugs are common inhabitants. However, research on sea slug in Taiwan still remains deficient. Between June 2004 and May 2006, surveys on the western coast of the Kengting Peninsula, the northeastern coast of Taiwan, Lan Yu, Green Island, Liuchiu Island, and Penghu were conducted for sea slugs. In total, 4 suborders, 14 families, and 105 species were recorded; 85 species were new records, and 6 were possible new species. Among these 105 species, specimens of 44 species in 8 families were available for investigation of spicule morphology which has been considered as an uninformative taxonomic character. Five types of spicules were recognizable in which the spindle-like type had broadest distribution among the species and is considered as the plesiomorphic character state. A possible autapomorphic type was found in Phyllidiella pustulosa; this status can be ensured until spicules of other congeners are known. Distribution of the other two spciule types provided information for a hypothesis for the family phylogenetic interrelationship which shows certain agreement with existing phylogenetic hypotheses. In Dorididae and Chromordorididae, distribution of the spicule types showed no spatial discrepancy in the whole animal, whereas such discrepancy pertained in Phyllidiidae. More information on spcicule morphology are needed before their taxonomic importance can be justified.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22253号 / 理博第4567号 / 新制||理||1656(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 柴田 一成, 准教授 浅井 歩, 教授 一本 潔 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

Genes present in multiple copies and genes that contain regions of repetitive sequences can undergo concerted evolution, which results in homogenization of the nucleotide sequence of the genes or repetitive regions. In regions of tandem repeats, this occurs through misalignment of repeat units followed by unequal crossover, which generates two products with differing numbers of repeat units. Gene conversion is thought to lead to one of these products becoming fixed in a species. The homogenous sequence of previously studied genes that have been thought to undergo this process has made it difficult to determine the exact models involved. Here I examine concerted evolution in SM50, a sea urchin gene that encodes a protein involved in biomineralization. The repetitive region in the SM50 gene varies in length between species, and there is variability in each repeat unit as well. I examine the codon usage in SM50 in a variety of species, and discuss how purifying selection, substitutions, concerted evolution, and selection at the level of DNA sequence have played a role in the evolution of this gene. I also examine the structure and sequence of the repeat units, and purpose models that have led to the evolution of the repeat pattern seen in the different species examined. Finally, I have found variation in the number of repeat units within several species. This has allowed us to deduce the specific models of unequal crossover that led to this variation. The unique variation in the repetitive region of SM50 has enabled us to describe a model of how substitutions affect the model of misalignment and unequal crossover.

The Pennsylvanian Marble Falls Formation in the Llano Uplift region of the southern Fort Worth Basin (Central Texas) is a Morrowan-Atokan mixed carbonate-siliciclastic unit whose deposition was influenced by icehouse glacioeustatic sea-level fluctuations and foreland basin tectonics. Previous interpretations of the Marble Falls Formation focused on outcrop data at the fringes of the Llano Uplift. This study uses a series of 21 cores to create a facies architectural model, depositional environmental interpretation, and regional sequence stratigraphic framework. On the basis of core data, the study area is interpreted to have been deposited in a ramp setting with a shallower water upper ramp area to the south and a deeper water basin setting to the north. Analysis of cores and thin sections identified 14 inner ramp to basin facies. Dominant facies are: (1) burrowed sponge spicule packstone, (2) algal grain-dominated packstone to grainstone, (3) skeletal foraminiferal wackestone, and (4) argillaceous mudstone to clay shale. Facies stacking patterns were correlated and combined with chemostratigraphic data to improve interpretations of the unit’s depositional history and form an integrated regional model. The Marble Falls section was deposited during Pennsylvanian icehouse times in a part of the Fort Worth Basin with active horst and graben structures developing in response to the Ouachita Orogeny. The resulting depositional cycles reflect high-frequency sea-level fluctuations and are divided into 3 sequences. Sequence 1 represents aggradational ramp deposition truncated by a major glacioeustatic sea-level fall near the Morrowan-Atokan boundary (SB1). This fall shifted accommodation basinward and previously distal areas were sites of carbonate HST in Sequence 2 deposition following a short TST phase. Sequence 3 represents the final phase of carbonate accumulation that was diachronously drowned by Smithwick siliciclastics enhanced by horst and graben faulting. These findings contribute to our understanding of the depositional response to glacioeustatic sea-level changes during the Pennsylvanian and can also form the basis for constructing a sedimentological and facies analog for Morrowan to Atokan shallow- to deepwater carbonates in the Permian Basin and the northern Fort Worth Basin. / text