| Ascarid, the most prevalent of the intestinal helminth infections that colonize the small intestine, has been reported in many rare wild animals such as giant panda, red panda, Ursidea, Canidae and Felidae. Accurate ascarids species identification is important in veterinary, medical and socio-economic. A phylogenetic scenario of ascarid nematodes has been proposed based on morphological characters. However, structural features of ascaridoids, particularly external parts, have considerable variations among genera and species. Likewise, their life cycles also show a diversity of patrns. Although many general features of ascaridoid life cycles have been established, detailed studies have been limited to relatively few species, and in some cases, recent investigations have yielded new findings. Analyses based on molecular characters rather than on morphology are employed in the study of ascarid nematodes phylogeny to verify the previous findings. The application of molecular approaches may provide important evidence clarifying the taxonomic status and the relationships among different spieces of ascarids. To identify the relationship and taxonomic of ascarids from these 21 wild animals, the Ribosome DNA 18s,28s and mitochondrial 12s genes were analysised which are different variation.Mainly study results and conclusions as follows:1 Sequence analysis of Ribosome DNA 18s, 28s and mtDNA 12s in ascarids of 21 species of wild mammals including giant panda.Sequencing and analysis of some parts of the ribosome gene 18s and 28s and mtDNA 12s was conduceted to investegate the relationship among roundworms from these 21 rare wild mammals including giant panda. The results indicated that the 12s gene showed a higher AT tendency. Divergence and identity analysis of the three genes showed that roundworms from these animals were distributed into five genuses:Toxocara cati toxa, Toxocara canis, Toxascaris, Baylisascaris and Ascaris. Homology analyses indicated that the identity levels of 18s genes sequence ranged from 98.5% to 100% among roundworms from all these 21 animals. Divergence levels of 28s genes sequences ranged between 14.9% and 15.8%, and between 14.7% and 15.1% compared Toxascaris with Toxocara cati and Toxocara canis, respectively. Divergence levels of intraspecies among other hosts were low, and no variability among interspecies was obsereved. Divergence levels of 12s genes sequences ranged from 11.7% to 12.8% between Toxocara cati and Toxocara canis. Homology analyses indicated that mt 12s gene appeared variability among intraspecies and interspecies. Phylogenetic relationship were inferred by three methods, NJ/MP/ML based on rDNA data,12s gene data and combined data. Evolution tree and the sequence diversities suggested that the ascarids of 21 species wild animal were classified into two families, four genera and seven species. The topologies showed that roundworms from A.melanoleuca, A.fulgens, U. arctos pruinosus, U. thibetanus mupinensis and U. arctos lasiotus were gathered together in one group with conspicuous confidence level in the three trees. Roundworms from Pan troglodytes, Hylobatesmoloch, Macaca mulatta and roundworms from Panthera tigris, Panthera tigris altaica, Panthera tigris amoyensis, Panthera tigris tigris, Puma concolor, Felis lynx, Canis lupus were gathered together with form the Ascaidoidea. Roundworms from Felis temminck, Prionailurus begalensis, Felis chaus, Alopex lagopu, Alopex Spitz were gathered together forms the Toxocaridae. All the taxa were included in a big branch tree. Four major groupings of species/genera were observed in the three trees:Toxocara spp., Baylisascaris spp., Ascaris spp. and Toxascaris spp... Meanwhile, the combined trees suggested that the genetic relationships of Baylisascaris ailuri are closer to Baylisascaris transfuga than those of Baylisascaris schroederi and received higher support (94%).2 Analysis of mitochondrial DNA cytb in Ascaris of 6 species wild mammals including giant panda.For the further investagation of the taxonomic status of Baylisascaris and Ascaris, the mitcochondrial partial cytb gene of roundworms from Ailuropoda melanoleuca, Ailurus fulgens, Ursus maritimus, Ursus thibetanus mupinensis, Macaca mulatta were sequenced. All the length of the partial sequences of cybt genes were 877 bp, including 382 variation sites and 267 parsimony informative sites. The third Condon position showed the highest mutation rate. Chosing the Anisakis simplex as the outgroup; NJ/MP/ML trees were constructed based on all cytb genes. The phylogentic trees indicated that the relationships of Baylisascaris ailuri from Ailurus fulgens are closer to Baylisascaris transfuga from Ursus maritimus and Ursus thibetanus mupinensis than those of Baylisascaris schroederi from AUuropoda melanoleuca meanwhile, Baylisascaris procyonis has a longer evelution distance than the other Baylisascaris in NJ trees. Roundworm from Macaca mulatta is closer to Ascaris suum. The results indicated that cytb gene is a good marker in the classification among intraspecies as its high mutation rate. |
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