Study On The Species Diversity And Molecular Systematics On The Digenea Of Fish In Taiwan Strait

The author had investigated the Digenea of fish-parasitizing in Taiwan Strait and did also the preliminary analysis of the molecular systematic on family level for the Digenea from year 2007 to year 2008.Totally had more than 82 species 728 individuals of fishes were investigated and 30 species of Digenea were obtained from them.Among them,12 species of Digena were observed,identified and discribed in this paper.There are 3 new species,2 undetermined species,2 reported species for the first time in Fujian Province and 5 reported species.1.Coitocaecum orthorchis Ozaki,19262.Podocotyle staffordi Miller,19413.Helicometra epinepheli Yamaguti,19344.Plagioporus xiamenensis n.sp.5.Plagioporus sillagonis Yamaguti,19386.Pleorchis sciaenae Yamaguti,19387.Phyllotrema guangxiensis Li et al.,19908.Aphanurus minimumsis n.sp.9.Derogenes xiamenensis n.sp.10.Lecithochirium sp.Yu,200511.Stephanostomum rachycentronis Shen,199012.Bucephalus sp.During the investigation,the author had observed that different species of Digenea can parasitize in the same species of fish at the same time.however,only one species of Digenea will be dominant in the fish after a period of time.So that,author concluded that competition might be occurred between them.Besides that,a species of Digenea could be found in both intestine and gills of their host simultaneity,In addition,the Digenea found in the gills were commonly smaller in their size exspecially species of Hemiuridae Luhe,1901,This phenomenon might be caused by specific structural characteristic of these kinds of Digenea which possess stronger adaptation of parasitizing in gills.In this paper,several families of Digenea which have attracted severe controversy regarding to their phylogenesis and taxonomic status were studied preliminarily by means of molecular systematic analysis.Phylogenetic trees were constructed by analysing the gene sequences according their 18SrRNA.The results showed that each branch of the tree was constructed by species from one family.It is conceivable that their ancestors may be multiplication since the species of Digenea is incredibly numerous.