| The Marine species of Taiwan,China,account for 1/10 of the world’s species,among which the mangrove ecosystem is characterized by high biodiversity and is distributed throughout the western coast of Taiwan.In order to explore the composition of meiofauna,especially the community structure of marine nematodes in mangrove wetlands in Taiwan Province,sediment samples were collected from 10 stations in February 2021 and January and February 2022.Including Danshui District of Xinbei City,Dayuan District of Taoyuan City,Xinfeng Township of Xinzhu County,Zhunan Town of Miaoli County,Gaomei Wetland of Qingshui District of Taizhong City,Budai Town of Jiayi County,Xiehu District of Qigu District of Tainan City,Sicao Wetland of Qigu District of Tainan City,and Jiangongyu of Jincheng Town and Guningtou of Jinning Township of Jinmen County.In this study,morphological methods were used to classify meiofauna,especially marine nematodes,and DNA barcoding was used to identify the dominant genera of marine nematodes.The main results are as follows:（1）More than 17 groups of meiofauna were found,including marine nematodes,copepods,oligochaetes,polychaetes,turbellaria,gastropoda,tardigrada,foraminifers,bivalves,rotifera,cnidaria,zanthozoans,cladicorns,amphipoda,isopoda,insects,ventral trichochetes and other unidentified species.Marine nematodes were the dominant group,accounting for 85.92%of the total abundance of meiofauna.From the point of tidal level distribution,mangrove wetland average abundance of meiofauna for（2955.58±2842.75）ind·10cm-2 in Taiwan Province.The results of one-way analysis of variance showed that there were no significant differences in the abundance and biomass of small benthos at H,M and L tidal level（P>0.05）,indicating that the abundance and biomass of microbenthos in mangrove wetlands in Taiwan Province were less affected by the change of tidal level distribution.From the perspective of geographical distribution,the abundance trends of meiofauna are as follows:Jinmen Island（7836.76±5223.48）ind·10cm-2>The north of Taiwan（2754.73±2547.05）ind·10cm-2>The south of Taiwan（2734.66±506.84）ind·10cm-2>The middle of Taiwan（753.95±832.16）ind·10cm-2,the change trend of meiofaunal biomass in accordance with the change trend of abundance.The results of one-way analysis of variance showed that there was a significant difference in the abundance of meiofaunal between the mangrove wetlands in Jinmen Island and the mangrove wetlands in the middle of Taiwan（P<0.05）,indicating that the abundance of meiofaunal in the mangrove wetlands in Taiwan Province was affected by the change of geographical distribution to some extent.（2）A total of 5805 marine nematodes were identified in the mangrove wetlands in Taiwai,belonging to 24 families,60 genera and 148 species.The dominant genera（dominance≥5%）were Daptonema（17.98%）,Ptycholaimellus（15.84%）,Neochromadora（7.5%）and Admirandus（6.52%）.The dominant species（dominance≥5%）were Ptycholaimellus sp1（10.93%）,Daptonema quattuor（8.15%）,Admirandus belogurovi（5.84%）and Ptycholaimellus ocellatus（5.45%）.The similarity percentage analysis showed that the cumulative contribution rate of marine nematodes at different geographic locations and tidal levels was above 90%.Among them,Daptonema is the main contributing genus in each geographical location and each tidal level.Geographically,the contribution rate of Daptonema was the highest in the middle Taiwan（74.42%）,followed by Jinmen Island（54.81%）,the northern Taiwan（11.44%）,and the southern Taiwan（4.19%）.In terms of tidal level,Daptonema was highest at the L tidal level（29.02%）,followed by the H tidal level（13.67%）and the M tidal level（17.17%）.The diversity analysis results showed that the number of marine nematodes in mangrove wetlands in Dansui district of Xinbei City and Jiangongyu in Jincheng town of Jinmen County was the highest,with28 species.The richness index,diversity index and dominance index of marine nematodes in Dansui district of Xinbei City were the highest.The number of marine nematodes in Dayuan district of Taoyuan City was the lowest（only 11）,and the richness index was the lowest,but the evenness index of marine nematodes was the highest.CLUSTER cluster analysis showed that the similarity of marine nematode community structure was affected by geographical location to a certain extent,that is,the similarity of marine nematode community was higher between the same geographical location or close geographical location.However,the similarity of marine nematode community structure was basically not affected by the tide position,whereas the marine nematode community showed an aggregation trend at each station,indicating that the similarity of marine nematode community between the same station was high.Marine nematodes feeding types was 2A（33.46%）>1B（32.81%）>2B（31.16%）>1A（2.58%）.2A,1B and 2B dominated the abundance,the sum of three reaching 97.42%,and1A was the least.According to the distribution of tidal levels,1B,2B and 2A at H and L tidal levels were equally dominant,but M tide was 2A.In terms of geographical location,the feeding types of nematodes in the northern of Taiwan,the middle of Taiwan and Jinmen Island were mainly（1B+2B）,followed by 2A and 1A,but the south of Taiwan is dominated by 2A.Marine nematodes average age structure and sex ratio was female>male>juveniles,females dominated the community,followed by males,and juveniles was the least.The ratio of male to female was 2.03:1.From the tidal level,the sex ratio of marine nematodes at each tidal level was similar,the female was about twice that of the male,and the juveniles was the least.From the geographical location,in addition to the middle of Taiwan was female>juveniles>male,the north of Taiwan,the south of Taiwan and Jinmen Island were females>male>juveniles.（3）11 new species of marine nematodes and 1 new record were measured,photographed,mapped,described and discussed in detail.The new species belongs to 7 families and 8 genera,they are Trissonchulus jiangongyuica sp.nov.and Trissonchulus zhunansis sp.nov.in Ironidae;Belbolla forkyspicula sp.nov.in Enchelidiidae;Halichoanolaimus sicaosis sp.nov.in Selachinematidae;Dorylaimopsis jinmendaoica sp.nov.,Paracomesoma fourteensup sp.nov.and Paracomesoma paralissum sp.nov.in Comesomatidae;Parodontophora jinmendaoica sp.nov.and Parodontophora micros sp.nov.in Axonolaimidae;Mesacanthion guningtou sp.nov.in Leptosomatidae;Subsphaerolaimus danshuisis sp.nov.in Sphaerolaimida.The new record belongs to 1 family and 1 genus,Axonolaimus arcuatus Schuurmans Stekhoven,1950 in Axonolaimidae.In the study of new species,pictorial search tables for 5 genera and male morphological data scales for 6 genera were presented.Besides,the thesis presents the list,the photographs and morphological descriptions of marine nematodes in mangrove wetlands in Taiwan Province.（4）In this study,based on the morphological classification of Sabatieria falcifera,Sabatieria sp,Sphaerolaimus longispiculatus and Tripyloides marinus in the mangrove wetlands of Taiwan Province,18S r DNA sequence,28S r DNA sequence and mt COI gene sequence were used as DNA barcoding to construct phylogenetic trees and provide evidences for molecular studies on the basis of morphological identification. |
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