| Acanthocephalans in the Pomphorhynchus are endoparasitic in fishes, with a total of24species recognized widely in literature. Species of Pomphorhynchus have been reported from plates of Pacific Ocean, Eurasia, Indian Ocean, Africa, and America.Pomphorhynchus fuhaiensis n. sp. was collected from the middle and posterior intestine of Abramis brama orientalis, Leuciscus idus, Cyprinus carpio, Carassius carassius and Tinca tinca, from Ulungur Lake (47°22’57.9"S;087°47’03.4"W) in Xinjiang Uygur Autonomous Region of China.6of23(26%) A. brama orientalis were infected with1-20(5) worms each,3of5(60%) L. idus infected with1(1) worms,4of4(100%) C. carpio with14-31(19) worms,3of5(60%) C. carassius with1-40(15) worms,2of8(25%) T. tinea with1-2(1.5) worms. Trunk almost cylindrical, enlarged in the middle, possessing15-17longitudinal rows of each9-12hooks (rarely9,10). Proboscis armature nearly equal in both sexes. Neck (between proboscis and trunk) is clavate, tapered and broader at base, forming a large round symmetrical bulb, posterior to proboscis. Proboscis receptacle extends through the neck and into the trunk. Mean neck:body ratio is about0.5. Lemnisci are equal, claviform, broader posteriorly, and extending beyond proboscis receptacle. Testes pre-equatorial, nearly equal, ovoid-spheroid, usually contiguous. Six pyriform cement glands are fusing posteriorly into2common cement reservoirs. Saefftigen’s pouch just posterior to cement glands, male reproductive system4.76-6.60(5.53) mm long, occupying39-48%(42%) of total length. Eggs are fusiform, with polar prolongation. The length and width of uterine bell, uterine, vagina are378-540(μm (475)X142-164μm (153);1.93-2.40mm(2.12)×112-178μm (151);220-428μm (336) X34-82μm(62). Female reproductive system occupying17-26%(20%) of total length.The complete mitochondrial (mt) genomes of5species in the Pomphorhynchus, representing16geographical populations, were obtained by common PCR and long PCR. These genomes are circular, double-stranded DNA molecules. All of these mt genomes have12protein coding genes, and there is some similarity among the amino acid sequences of these genes. Two rRNAs have the same arrangement in the mt genomes, but the22tRNAs differ in the arrangement among the mt genomes. All the36genes are coded in the same strand. Codon usages are different in different species of Pomphorhynchus. The most frequently used codons in Pomphorhynchus are TTA、 GGG、 GTG. Amino acid usages are also different, with the most frequently used amino acids being Val, Leu, Gly. The nucleotide polymorphism of the complete mt genomes is distributed in multi-region by sliding window analysis. The nad5and atp6are among the highest mutation region except the noncodig region, and the nad2and rrnS have a high level of mutation, with relatively high level also found in part of the cox3, nad1and cob.Phylogenetic analysis on the basis of these mt genomes indicates that Pomphorhynchus laevis and P. tereticollis should be considered as separate species. P. laevis collected from continental Europe was clustered in a same branch, but P. laevis collected from England was clustered in a same branch with Pomphorhynchus tereticollis from the continental. P. fuhaiensis had a close relationship with P. laevis from continental Europe. The origin and divergent time of species in the Pomphorhynchus were estimated by BEAST1.4.6. The origin of common ancestor of Pomphorhynchus was in late-Jurassic, being about152.66Ma before. Pomphorhynchus bulbocolli and P. rocci were diversified in late-Oligocene, about23.9Ma before; P. laevis and P. tereticollis diversified in early-Paleocene, about65.44Ma before. However, other Pomphorhynchus species should be included in the phylogenetic analysis in order to illustrate the clear phylogenetic relationship of species in the genus and their diversification.The complete mt genome of Pallisentis celatus is a circular, double-stranded DNA molecule (13,855bp). The nucleotide composition of the entire P. celatus mt genome sequence is40.8%T,28.8%G,20.7%A, and9.7%C and the overall A+T content is61.5%. The mt genome contains36genes including12protein coding genes,22tRNAs and2rRNAs (rrnL and rrnS), with all genes encoded in the same strand. The total length of the12protein coding genes is10,041bp, which consist of3,347codons, with the exclusion of termination codons. Analysis of the codon usage of the12protein coding genes revealed that three codons are used frequently. The TTT codon is used most frequently (8.98%), followed by TTG (7.40%) and GTT (6.92%). The most frequently encoded amino acids include Val (15.84%), Gly (10.82%) and Ser (10.60%)(Serl:5.64%, Ser2:4.96%), accounting for37.26%of total amino acid components.22tRNAs encoded by the mt genome of the P. celatus, vary in length from49(trnD) to69(trnC) nucleotides, including two trnL and two trnS.Comparison of the gene order in P. celatus with those in Leptorhynchoides thecatus and O. luehei reveals that P. celatus has identical gene arrangement with L. thecatus, and has almost identical gene arrangements with Oncicola luehei, with the only difference being the two reciprocal translocations of tRNAs between trnK and trnV, and between trnSl and trnMthat are directly adjoined to each other, respectively. Phylogenetic analysis based on36species of complete mt genome sequence data were obtained in BI and ML analyses with Montastraea annulari (Cnidaria) as an outgroup. Three acanthocephalan species, P. celatus, L. thecatus and Oncicola luehei form a clade with high nodal support, among which, P. celatus and L. thecatus form a clade, and then with O. luehei. Acanthocephala is much more close to Bdelloidea than to Monogononta, froming together a clade of Syndermata. However, further analyses in respect of genetic relationship of acanthocephalans and their relationship with rotifers should be carried out with more species of acanthocephalans representing different taxonomical groups. |
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