Taxonomy Of Bdellidae In China

Bdellidae（Acariformes:Trombidiformes:Prostigmata:Bdelloidea）are medium to large sized predatory mites and are a potential predatory mite resource that has been indicated to be effective biological control agents on small arthropods,including pest mites,springtails,and other small insects.Bdellidae currently includes five subfamilies and 283 valid species all over the world,and four subfamilies and 26 valid species in China.The taxonomy of Bdellidae is mainly about species description,and there are few studies on their phylogeny,ontogeny and comparative morphology.In China,Taxonomical study of Bdellidae is unbalanced,and most happened in southern China（mainly in Taiwan and Fujian）,which showed that its level was lagged behind the world.In this thesis,systematic taxonomic research was conducted,and more species were established or found,which increase dramatically the species diversity of Bdellidae in China.Meanwhile,analysis of comparative morphological characteristics of Bdellidae,characteristics of Chinese fauna and phylogenetic relationship were also carried out.The reults are as follows:1.ClassificationIn this study,4556 bdellid specimens were collected from 1002 sites in 22 provinces,municipalities and autonomous regions in China,and 2000 slide specimens were made.Sixty species were identified,including one new recorded genus,25 new species,six new recorded species and three undetermined species.And the proportion of Chinese Bdellidae has increased from 9.19%to 22.81%of known species from the whole world.Besides,250feature plates were produced,and a key to the species,genera and subfamilies of Chinese Bdellidae were compiled.Details are as follows:New record genus to China:Trachymolgus Berlese,1923.25 new species:Spinibdella forkus sp.nov.,Spinibdella scobis sp.nov.,Spinibdella jinheensis sp.nov.,Spinibdella octosetalis sp.nov.,Biscirus huaxiensis sp.nov.,Biscirus huangshanensis sp.nov.,Biscirus kanasiensis sp.nov.,Biscirus rottenwoodus sp.nov.,Cyta xinyangensis sp.nov.,Cyta quadrisetalis sp.nov.,Cyta tuanlongensis sp.nov.,Cyta pseudokreiteri Wu&Guo,2021,Neomolgus lujiaoensis sp.nov.,Neomolgus bomiensis sp.nov.,Odontoscirus cavernicolus sp.nov.,Odontoscirus prunus sp.nov.,Odontoscirus brevisetalis sp.nov.,Odontoscirus jini sp.nov.,Odontoscirus anzhouensis Wu&Guo,2021,Odontoscirus yinggeensis sp.nov.,Odontoscirus rhododendron sp.nov.,Odontoscirus pseudokoloseta sp.nov.,Odontoscirus wallacei sp.nov.,Odontoscirus genheensis sp.nov.,Bdella xini Wu&Guo,2021.Six new records species to China:Spinibdella denheyeri Hernandes,Daud&Feres,2008,Cyta kreiteri Barbar&Ueckermann,2017,Neomolgus aequalis（Schweizer&Bader,1963）,Odontoscirus amamiensis Shiba,1985,Odontoscirus malayensis Shiba,1978,Odontoscirus nippocirus,1985.Three undetermined species:Trachymolgus sp.,Neomolgus sp.1,Neomolgus sp.2.2.Comparative morphologyAdults:Four subfamilies,eight genera and 52 species of Bdellidae in China were included in the study of morphological comparison.The results showed that the number of ventral hypostomal setae on subcapitulum,the shape of chelicerae,and the presence or absence of trichobothria on legs are the main stable taxonomic characteristics between the subfamilies;the number of ventral hypostomal setae subcapitulum and setae on chelicerae,the presence or absence of trichobothria on legs,the presence or absence of lateral proterosomal setae,and the number of ended setae on palp are taxonomic characteristics of between the genera;the number of ventral hypostomal setae,and striae on subcapitulum,palp chaetotaxy,the shape of the dorsal and ventral setae on body,and legs chaetotaxy are difference between the genera and species,which can be applied in the identification of genera and species in Bdellidae.Setae c₁,c₂,d₁,e₁,f₁,f₂,h₁,h₂ and three cupules（ia,im,ip）on dorsal positions are relatively stable,which should not be used as a distinguishing feature for the classification of Bdellidae.Ontogeny of Bdellidae:Ontogeny changes of Bdellidae are mainly focused on ventral hypostomal setae（vh）,setae on palpal basifemur,aggenital setae（ag）,genital setae（g）,adanal setae（ad）,and leg setae.And the change are as follows:Subcapitulum:There is an increasing tendency of vh on adult subcapitulum with six pairs of setae,and with two,three,four,five,and six setae,respectively with the stages from larvae to adults.While there is no change of vh on adult subcapitulum with two pairs of setae.Palp:palpal setae are relatively stable,except on basifemur,which increase with the stages.Genital region:There is no g and ag in lava stage,one pair of g and 1–4 pair（s）of ag in protonymph,and more in later stages.Legs:There are three pairs of legs in larvae,while four legs in other stages.Femora of all legs in larvae are undivided,of legs I-III divided into basifemora and telofemora from protonymph to adult stages,and of legs IV divided into basifemora and telofemora from deutonymph stage.The setae on legs are increasing with the stages.From above all,we can know the sequence of leg occurrence should beⅠ–Ⅲ,thenⅣ.3.Faunal analysisIn this study,we use the statistical method of every unitary pattern and accumulated patterns to analyse the distribution of Chinese Bdellidae species,and discussed their distribution types and faunal characteristics in zoogeographic divisions of the world and China.The results indicated that there are 60 species of Bdellidae in China,20 species（33.33%）belong to the Oriental pattern only,and 27（45.00%）species belong to the accumulated patterns containing the Oriental,and 47 species（78.33%）belong to the Oriental and accumulated patterns containing the Oriental.The Palaearctic is weaker than the Oriental,followed by the Nearctic,the Neotropical,the Australasian,the Australasian.Thus,the Chinese fauna of Bdellidae is typical of the Oriental.In zoogeographic divisions of China,the Central China Region has the most obvious advantages,19 species（31.67%）belong to the Central China Region,and 10 species（16.67%）belong to the accumulated patterns containing the Central China Region,and 29 species（48.33%）belong to the Central China Region and accumulated patterns containing the Central China Region.The South China Region is weaker than the Central China Region,followed by the Southwest China Region,the Northeast China Region,the Mongolia-Xinjiang Region,the Qinghai-Tibet Region;the weakest connection with the North China Region.Therefore,Chinese fauna of Bdellidae is typical of the Central China.4.Phylogenetic analysisIn this study,57 external morphological characters of adult Bdellidae from 11 genera and 45 species were selected for phylogenetic analysis.The adults showed that the monophyleticity of Bdellidae,Cytinae,Spinibdellinae and Odontoscirinae are all well supported.However,the monophyly of Bdellinae is not supported,with Hexabdella and Bdella forming a paraphyletic group.We think Hexabdella should be a subfamily.The genera of Hexabdella,Bdella,Polytrichus,Odontoscirus,Neomolgus,Monotrichobdella,Biscirus,Tetrabdella,Spinibdella are all individually form a monophyletic group whose monophyletism are supported.Odontoscirus is a paraphyletic group.Cyta and Trachymolgus of Cytinae did not form two monophyletic groups,but a polyphyly.We think Cyta and Trachymolgus should belong to Cyta.The result not supported the nowadays classification system of 11 genera,five subfamilies of Bdellidae.And their phylogenetic relationship should be 10 genera,six subfamilies of Bdellidae:（Hexabdellinae,Hexabdella+（Bdellinae, Bdella+（Polytrichinae,polytrichus+（Odontoscirinae（Odontoscirus+Neomolgus））））+Cytinae,Cyta+Spinibdellinae（Monotrichobdella+Biscirus+Tetrabdella+Spinibdella））.