Thirty-five species of chaetognaths belonging to fourteen genera and four families were identified in the waters of southwestern Taiwan from July 2009 to April 2010. In surface tows, thirty-five species of chaetognaths belonging to fourteen genera and four families were found, with mean abundance of 2911 ¡Ó 586 ind./ 100m3; in oblique tows, thirty species of chaetognaths belonging to fourteen genera and four families were identified, with mean abundance of 3180 ¡Ó 532 ind./ 100m3. The five predominant species were Flaccisagitta enflata, Aidanosagitta regularis, A. neglecta, A. delicate and Serratosagitta pacifica, together they constituted 72 % of the total catch. The hydrographic conditions in the waters southwestern Taiwan were affected by seasonal monsoons and water masses. Higher temperature, lower salinity, and higher nutrient concentration were found in summer, and lower temperature, higher salinity, and lower nutrient concentration in winter. Generally higher abundance of chaetognath was found in summer and in inshore waters, and lower in spring and in offshore waters. Furthermore, the abundance of chaetognath showed significantly positive correlation with copepods, but no significant correlation with temperature and salinity. The predominant chaetognaths were mostly stage I (47 ~ 89 %), adult stage(>stage III) was mainly found in April. The average body lengths (ABL) of Fl. enflata, A. regularis, A. delicate and Se. pacifica were larger in spring than in summer, while the ABL of A. neglecta exhibited larger in winter than in summer and autumn. This study implies that the distribution of weight mean stage (WMS) and ABL of chaetognath were likely influenced by the water masses, because the ABL of Fl. enflata and WMS of Se. pacifica were larger in high salinity waters, furthermore, this study found that the seasonal moonsons and the succession of water masses maybe played important factors in the distribution patterns of chaetognaths.

This study aims to study the species composition and distribution of chaetognaths in the waters surrounding Taiwan January 2005 to July 2006, and to explore the relationship between environmental factors and their dynamic distribution. Waters surrounding Taiwan are affected by monsoons and water masses. In winter, the northwestern Taiwan area is under the impact of low-temperature low-salinity China Coastal Current, but in summer, Taiwan Strait is affected by South China Sea Current going northward with high-temperature and high-salinity. As for eastern waters of Taiwan, Kuroshio current passes throughout the year so it is high-temperature and high-salinity. In July 2006, when three typhoons struck Taiwan, excessive fresh water from land flowed into the ocean and stations along the coast where low in salinity. This study identified a total of 28 species of chaetognath under 14 genera of 4 families, with average abundance at 475 ¡Ó 35 ind./100m3, which shows an obvious change related to seasons, relatively low in winter and spring and high in summer and fall. The seven most dominant species are: Flaccisagitta enflata, Serratosagitta pacifica, Zonosagitta littoralis, Pterosagitta draco, Aidanosagitta regularis, Aidanosagitta bedfordii and Aidanosagitta neglecta, accounting for 85% of the total abundance. The distribution of chaetognath in waters surrounding Taiwan is affected by the different water masses. The northwestern area where China Coastal Current passes through has high abundance but less number and low Shannon diversity index, but the eastern and southern waters dominated by Kuroshio current shows a completely different trend. From the results of multiple regression analysis, it is found that the abundance of chaetognath and F. enflata are in positive correlation with that of the abundance of copepod, indicating that the quantity of food might be a factor affecting the distribution of chaetognath. The second dominant species S. pacifica has no relation with hydrographic or biological factors, and the third dominant species Z. littoralis is in negative correlation with temperature and salinity. Along with the results of indicator species analysis, Z. littoralis can possibly be used as indicators species of China Coastal Current. The three predominant species are dominated by the Stage I and significantly less in other growth stages. The average body lengths (ABL) of F. enflata and S. pacifica are the larger in spring and smaller in fall, with obvious changes with seasons, but that of Z. littoralis is larger in winter and summer and smaller in spring and fall. Different water masses have impacts on distribution of weight mean stage (WMS) and ABL of chaetognath; for example, F. enflata and S. pacifica with the equivalent growth have larger bodies in Kuroshio current than in China Coastal Current, but Z. littoralis which prefers cold water shows an opposite trend. In addition, this study found that abundance, species, Shannon diversity index, WMS and ABL of chaetognath has no differences between day and night, but the succession of water masses in waters surrounding Taiwan may be an important factor affecting the distribution patterns of chaetognaths.

Seventeen species of chaetognaths belonging to nine genera and three families were recognized from the samples collected in estuaries of Tamshui River and Kaoping River from February 2003 to November 2003. In Tamshui River estuary, eleven species belonging to eight genera and three families were recorded, with the mean abundance of 807 ¡Ó 1154 ind./100m3, while in Kaoping River estuary, fourteen species belonging to nine genera and three families were identified, with the mean abundance of 1601 ¡Ó 2796 ind./100m3. The three most dominant species in both estuaries were Flaccisagitta enflata, Aidanosagitta crassa and A. neglecta, and together they comprised ¡Ö95¢Mof the total chaetognaths. The abundance of chaetognaths showed apparent seasonal changes, higher abundance in February in Tamshui River estuary and in May in Kaoping River estuary. The abundance of chaetognaths showed no significant correlation with temperature in both estuaries, but displayed higher relationships to salinity and copepods. The body length¡]BL¡^ of Flaccisagitta enflata showed significant seasonal and spatial differences, with larger in both February and May in Tamshui River estuary but only in May in Kaoping River estuary. Aidanosagitta crassa showed significantly larger in BL in February than in other months in Tamshui River estuary, but it was not in Kaoping River estuary. The stage I of chaetognaths dominated in this study area and occupied ¡Ö80¢Mof the total count. Other stages mostly presented in February in Tamshui River estuary and in May in Kaoping River estuary. Only Fl. enflata was found to have gut content, all copepods, in February and May. The estimated daily predation impact on the standing stock of copepods ( by number ) was insignificant, only ¡Õ1¢H in both estuaries.

The phylum Chaetognatha is a mysterious group of organisms that has eluded scientists for more than a century because of their unique morphology and developmental characteristics, i.e. protostome (mouth develops from blastopore; e.g. mollusks, annelids, arthropods) versus deuterostome (anus develops from blastopore; e.g. echinoderms and chordates) offer few clues to their evolutionary origins. Some early morphological studies argued that chaetognaths were derived mollusks or nematodes according to gross ultrastructural data, while other studies focused on the coelomic cavity. 33 Although 18S rRNA is widely used in molecular phylogeny studies, it has limits such as long- branch chain attractions and a slow rate of evolutionary change. Long-branch chain attractions are a phenomenon in phylogenetic analyses when rapidly evolving lineages are inferred to be closely related, regardless of their true evolutionary relationships. Hence other genes are used in this study to complement the 18S rRNA such as the cytochrome oxidase genes. The cytochrome oxidase genes are highly conserved throughout all eukaryotic organisms and they are less ambiguous to align as compared to the ribosomal genes, making them better phylogenetic markers as compared to the 18S rRNA gene. This study focuses on using a molecular approach (ARDRA, PCR, phylogenetic tree reconstruction) to determine the phylogeny of pelagic chaetognaths found on Pelican Island, Galveston, Texas. 18S rRNA, Cytochrome Oxidase I and Cytochrome Oxidase II genes were used to help decipher the phylogeny of this group. All analyzed genes in this study (18S rRNA, COI, and COII) grouped the Pelican Island chaetognaths with the protostomes. The maximum parsimony bootstrap tree for the 18S rRNA gene, grouped the samples closest to the arthropods (protostome). For the COI and COII genes, the minimum evolution bootstrap tree grouped the 8 collected samples more closely to two other protostome phyla: the mollusks and annelids (COI) while bootstrapping with the COII grouped the samples with the nematodes (with >66 percent bootstrap). My findings are significant because they reveal phylogenetic results of a protostome lineage for the Chaetognatha using 3 genes, one of which (COII) has not been greatly studied for the Chaetognatha.