Taxonomy Of Some Species Of Hemiarthrinae(crustacean:Isopoda)from The Indo-west Pacific Ocean And Structural Analysis Of The Complete Mitochondrial Genome Of Diplophryxus Sp.

The subfamily Hemiarthrinae belongs to phylum Arthropoda,subphylum Crustacea,order Isopoda,suborder Epicaidea,superfamily Bopyroidea,family Bopyridae.Up to now,there are 64 species of 29 genera in the subfamily Hemiarthrinae,which are mainly distributed in the Indian Ocean,Pacific Ocean and Atlantic Ocean,and most species are attached to the abdomen and ventral surface of the order Caridea.At present,domestic and foreign researches on this subfamily are based on taxonomic studies of morphological characteristics,and there are only a handful of studies on the global geographic distribution and phylogeny of this group.Hemiarthrinae has a special parasitism way that is different from other subfamilies of the family Bopyridae.Its species identification,geographic distribution,and host distribution groups have an important influence on perfecting the origin and evolution of this family,and inferring its evolutionary route.Therefore,this article has carried out a detailed taxonomic description of the morphology of the four species distributed in the Indo-West Pacific Ocean;Based on the morphological characteristics,and by comparing the key characteristics of females,a key to the subfamily Hemiarthrinae and the genera of Hemiarthrus and Diplophryxus,laying the foundation for subsequent research on this subfamily;Summarize the host and geographic distribution of 64 species of abdominal bopyrids distributed around the world;Obtained the complete mitochondrial genome sequence of Diplophryxus sp.for the first time,constructed a phylogenetic tree,clarified the taxonomic position of the subfamily Hemiarthrinae in the branch,and speculated its phylogenetic relationship.The main research contents and results are as follows:1.Taxonomy research: Completed the morphological identification and comprehensive description of 4 species in the western Indo-Pacific waters.Including3 new species,they are the Allodiplophryxus unilateralis An,Chen & Paulay,2020 collected in Western Australia,the Loki athanus An,Chen & Paulay from Madagascar,and the Hemiarthrus alphei An,Chen & Paulay,2020 from French Polynesia.A summary analysis of all taxonomic records of the type species of the genus Diplophryxus,Diplophryxus jordani Richardson,1904,was analyzed,and the taxonomic research status of this genus was discussed.Based on the female morphological characteristics of the subfamily Hemiarthrinae,the frontal lamina,pereopod,coxal plate,lateral plate,pleopod and uropod and other key identification features,the complete key to the subfamily Hemiarthrinae and 4 species of Hemiarthrus and 8 species of Diplophryxus were compiled.2.Geographical distribution and host situation analysis: The global distribution of 29 genera and 64 species of the host and geographical distribution of the subfamily Hemiarthrinae is statistically summarized.On this basis,the current situation of the geographical distribution of all species in the subfamily is analyzed and summarized and species are mainly parasitized in 39 genera of 12 families under the order Caridea.The geographical distribution of this subfamily is in many other sea areas except the Antarctic,and the three oceans are almost equally distributed,accounting for 1/3 of each.Among them,the sea areas with relatively concentrated geographical distribution are the South China Sea(9 species)and the Japanese sea(12 species).3.Whole mitochondrial genome structure: For the first time,a complete mitochondrial genome structure analysis of the subfamily Hemiarthrinae.The whole mitochondrial genome of Diplophryxus sp.is 14346 bp in length,with A + T content of 61.81% and G + C content of 38.19%,showing obvious AT bias.A total of 36 genes,including 13 protein coding genes,2 r RNA genes(12S and 16S),21 t RNA genes and trn I gene deletion.The protein coding gene uses 6 start codons(ATA,ATC,ATG,ATT,TTG,GTG)and 3 stop codons(TAA,TAG,T––).The sequence length of t RNA is between 52 and 62 bp.The longest sequence is trn S1 gene,and the shortest sequence is trn C gene.Most t RNAs fold into a typical clover structure,except that trn C lacks the DHU arm,trn G and trn R lack the T?C arm.Compared with the putative isopod ground pattern,Diplophryxus sp.has a unique gene order,and trn R and trn S1 genes exhibit rearrangements.4.Phylogenetic analysis: The data set used the amino acid data of 13protein-coding genes in the mitochondrial genomes of 55 existing isopod species in Genbank,and used the heterogeneous CAT-GTR model most suitable for isopods to construct a phylogenetic tree.The results showed that Diplophryxus sp.and Bopyroides hippolytes+Argeia pugettensis form sister branches,are closely related,and have the highest support value 1;used all the cox1 genes in the current database to construct BI and ML trees,which showed that Diplophryxus sp.is located in its relatively basic position and is not clustered with the subfamily Athelginae,which also verified that Hemiarthrinae and Athelginae are derived along completely different routes,and that the abdominal parasites are not monophyletic.