台灣多岐腸目扁蟲的分類學研究很少。本研究自2012年以來檢視台灣海洋扁形動物之多岐腸目扁蟲，並蒐集257份保存標本。依形態與解剖特徵鑑定29種，其中吸器亞目包含25個物種、無吸器亞目4個物種，台灣新記錄種21種。而黃點黑扁蟲 (Thysanozoon nigropapillosum) 則修正其原始描述，為具有白色邊緣與黃色疣點的正確外觀。相關大盤扁蟲 (Ilyella gigas)、馬崗扁蟲 (P. magangensis)等的攝食、生殖行為與野外族群變動等生態觀察，一併記錄與發表。
本論文依據形態特徵命名Pseudocerus(偽角扁蟲屬)的馬崗偽角扁蟲(P. magangensis)，以及新描述四個物種多彩偽角扁蟲 (Pseudocerus sp. 1), 合界偽角扁蟲 (P. sp. 2), 華麗偽角扁蟲 (P. sp. 3), 擬藍紋偽角扁蟲 (P. sp. 4)。儘管馬崗偽角扁蟲與近似物種外觀上顏色類似，但仍可與藍紋偽角扁蟲 (P. indicus)的背色與邊緣藍色點，與柯氏偽角扁蟲 (P. goslineri )體背細點的顏色，以及與藍帶偽角扁蟲(P. concinnus)的藍色背中線區別。解剖上的差異處本文也一併討論。
本研究使用粒線體COI 基因分析海扁蟲的多樣性，並應用於偽角扁蟲屬內物種的鑑定。12種偽角扁蟲種間平均遺傳距離為15.26%，最近與最遠遺傳距離分別為8.58%與21.69%。分子證據支持上述物種與馬崗偽角扁蟲及其他四種新描述種偽角扁蟲為不同物種。相對於28S基因，COI 基因有較高的種間遺傳距離，顯示COI 基因是較佳的扁蟲種類分子鑑定標記，尤其是具有許多近似種的偽角扁蟲屬。本論文結果顯示多岐腸目扁形動物的分類研究，同時需要形態與分子鑑定。

Marine turbellarian flatworms belonging to the order Polycladida have been collected from Taiwan since 2012. The 257 specimens included 25 species of Cotylea and four species of Acotylea identified according to their morphological and anatomical characteristics. The original description of Thysanozoon nigropapillosum (Hyman, 1959) regarding its color patterns on the papilla tips and body margin was erroneous. Instead, the species show color patterns with yellow-tipped papillae and a white body margin. The feeding, reproductive behavior and fluctuations in population of T. nigropapillosum, Ilyella gigas and Pseudoceros magangensis were also recorded and reported herein.
Of the 21 species newly found in Taiwan, four newly described species, Pseudocerus sp. 1, P. sp. 2, , P. sp. 3, P. sp. 4 and P. magangensis are classified as new species according to morphological evidences. P. magangensis has a background color pattern similar to that of congenerics P. indicus, P. goslineri, and P. concinnus. However, P. indicus has cream-white background coloration and blue marginal spots, P. goslineri has orange, pink, and brick red dots, while P. concinnus has a royal blue medium line. Further anatomical differences between these four species are described in this work.
A primer targeting at flatworm mitochondrial COI gene was designed and the sequences that allowed easy distinction of different species of the genus Pseudoceros was successfully obtained. The average genetic distance among the 12 species of Pseudoceros was 15.26%, with the shortest and longest being 8.58% and 21.69%, respectively. Molecular evidence shows that the four newly described species and P. magangensis are distinctive from other species. The higher divergent range of the COI gene sequences in the genus Pseudoceros shows that this gene sequence is a better molecular tool than 28S gene for identifying the Pseudoceros species with similar color patterns. This study shows the importance of using both morphological and molecular data for species identification.

論文審定書 ………………………………………………………………i
誌謝 ………………………………………………………………………ii
中文摘要 ………………………………………………………….……...iii
英文摘要 ……………………………………………..…………………..iv
Introduction …………………………………………………………… P.1
Biological description …………………………..……………….. P.6
Classification system ……………..………………..……….……. P.11
Molecular phylogenetics …………..…………….………………. P.13
Purposes of this study ……………..……………………..………. P.15

Materials and Methods
Specimen collection ………………………………………….…… P.17
Specimen database…………………………………………..…… P.17
Specimen preservation …………………….……….……….……. P.18
Histology …………….…………………….……….……….……. P.18
Primer design, DNA extraction, amplification, and sequencing … P.19
Phylogenetic analyses ……………..……………………………… P.20

Results
Species description ............................................................. P.22
Ilyella gigas (Schmarda, 1859). …………………………...……… P.23
Stylochoplana suoensis Kato, 1943. ……………..………….……. P.25
Callioplana marginata Stimpson, 1857. ………………………….. P.27
Paraplanocera oligoglena (Schmarda, 1859)…………………….. P.29
Enchiridium japonicum Kato, 1943. ……………………………… P.31
Phrikoceros diadaleos Newman & Cannon, 1996. ……………….. P.33
Phrikoceros katoi Newman & Cannon, 1996. ………………..…… P.34
Pseudobiceros bedfordi (Laidlaw, 1903). …………..……………... P.35
Pseudobiceros fulgor Newman & Cannon, 1994. ………………… P.36
Pseudobiceros hancockanus (Collingwood, 1876). ……………..... P.37
Pseudobiceros hymanae Newman & Cannon, 1997. …………....... P.38
Pseudobiceros strigosus (Marcus, 1950). ……………………...…. P.39
Pseudoceros sp. 1 newly described species ...……………..….… P.41
Pseudoceros concinnus (Collingwood, 1876). ……………..…….. P.43
Pseudoceros confusus Newman & Cannon, 1995. …………..…… P.44
Pseudoceros ferrugineus Hyman, 1959. ………………………… P.44
Pseudoceros goslineri Newman & Cannon, 1994. …………….… P.45
Pseudoceros sp. 2 newly described species ……………….…….. P.46
Pseudoceros imitatus Newman & Cannon, 1994. …………..……. P.47
Pseudoceros jebborum Newman & Cannon, 1994. ………....…… P.48
Pseudoceros magangensis new species .……………….….……… P.48
Pseudoceros sp. 3 newly described species ………..…...……… P.52
Pseudoceros sp. 4 newly described species …...………………..... P.53
Pseudoceros paralaticlavus Newman & Cannon, 1994. ………..… P.55
Pseudoceros scintillatus Newman & Cannon, 1994. ……...…..….. P.56
Pseudoceros scriptus Newman & Cannon, 1998. …………..…..… P.57
Pseudoceros rubrotentaculatus Kaburaki, 1923. …..……..…....… P.57
Thysanozoon nigropapillosum (Hyman, 1959). ………………….. P.58
Tytthosoceros lizardensis Newman & Cannon, 1996. ……………. P.61

Mitochondrial COI Gene Sequences Analysis
Sequence analysis of COI gene …………………………………… P.62
Substitution saturation test of the genus Pseudoceros ……….... P.63
Comparison of genetic distances among Pseudoceros species . P.63

Discussion ………………………………………………………….…. P.65
Re-description of Thysanozoon nigropapillosum (Hyman, 1959)… P.65
Morphological and molecular characteristics are both needed for identification ........................................................................................ P.68
Mitochondrial COI gene is a better tool for identification .............. P.71
More molecular markers are needed for future phylogenetic study of the order Polycladida
………………………………….…................................................. P.72
Feeding behavior of Thysanozoon nigropapillosum (Hyman, 1959)
…………………………………………………………....................... P.73
Unreported predatory behavior of Ilyella gigas (Schmarda, 1859).. P.74
Population fluctuation and mating season of Pseudoceros magangensis
………………………………………………...............................… P.75
Penis-gripping behavior of Thysanozoon nigropapillosum (Hyman, 1959)
………………………………………….................................... P.76
References ……………..……………………… ...………...…..….... P.78

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