Taxonomic Study Of Living Freshwater Ostracods From China, And Analysis Of Geographical Distribution

Ostracods,belonging the Arthropoda,Crustacea,Ostracoda,are small crustaceans with a calcified carapace and eight pairs of appendages.Ostracods are found throughout in most aquatic environments including freshwater,saline lakes and oceans.Ostracods are often considered as one of the oldest crustacean groups,and because of the well-calcified,bivalved shell,ostracods are better known from its abundant fossils,which providing evidences for paleontology.Since the first reported of living freshwater ostracod in 1776,there are 2330 described living non-marine ostracods in the world.But as to China there are more than one hundred reported Recent ostracods,including living and sub-fossil species.Up to now,there was no checklist of living freshwater ostracods has been reported.The present study was based on field collecting samples and consulting old literature,and 99 ostracod species was listed in the checklist and 71 species was described and remarked in detail.The detailed systematic of the eight species in genera Schellencandona Meisch,1996 and Pseudostrandesia Savatenalinton and Martens,2009 a respectively were studied basing on characters of carapace and soft parts.The relationship between genera Chrissia and Stenocypris was analyzed via the culture of Stenocypris species.After measuring lengths of carapaces collecting from the beakers for culturing,nine instar stages were found during their life,and the differences of carapace and soft parts between genera Stenocypris and Chrissia were studied.Additionally,the species diversity of the 99 species was also studied basing on Jaccard Similarity Coefficient,PAE analysis and so on.The results are summarized as follows:1.The present study makes the first checklist of living freshwater ostracods in China.There are 99 species belonging three suborders three superfamilies six families 16 subfamilies 40 genera.71 species of them are drawn,described and remarked in detail.Among them,seven species are identified as new: Cyclocypris n.sp.,Ilyocypris dui Ma and Yu,2018,I.luxiensis n.sp.,Pseudocandona n.sp.,Pseudocypretta lineata n.sp.,Schellencandona dui Ma and Yu,2018,Tonnacypris n.sp.Six genera are new for China: Batucypretta Victor and Fernando,1981 a,Microdarwinula Danielopol,1969,Pseudocandona Kaufmann,1900,Pseudocypretta Klie,1932,Trajancypris Martens,1989,Vestalenula Rossetti and Martens,1998.24 species are new for China,and 16 are identified: Bradleystrandesia reticulata(Zaddach,1844),Eucypris pigra(Fischer,1851),Ilyocypris monstrifica(Norman,1862),Microdarwinula zimmeri(Menzel,1916),Pseudocandona abei Smith and Janz,2008,Pseudostrandesia mamarilorum(Victor and Fernando,1981b),Stenocypris hirutai Smith and Kamiya,2006,S.malayica Victor and Fernando,1981 b,S.orientalis Victor and Fernando,1981 b,S.viridis Okubo,1990,Strandesia freyi Victor and Fernando,1981 b,Tanycypris alfonsi Nagler et al.,2014,T.centa Chang et al.,2012,T.siamensis Savatenalinton and Martens,2009 a,Trajancypris laevis(G.W.Müller,1900),Vestalenula cornelia Smith et al.,2006.Eight species are in open nomenclature: Batucypretta sp.,Candonopsis? sp.,Cypridoidea gen.et sp.indet.1,Cypridoidea gen.et sp.indet.2,Cyprinotus cf.kimberleyensis Mc Kenzie,1966,Fabaeformiscandona sp.,Pseudocandona sp.,Vestalenula sp.2.Some unidentified problems between species and genera during the systematic study of freshwater ostracods were studied.Including: keys to eight species in genera Schellencandona and Pseudostrandesia prospectively are given.Basing on the culture of Stenocypris species,nine instar stages are calculated via measuring lengths and heights of the valves.The relationship between Chrissia and Stenocypris is studied,septa along margins of valves are only present in the adult stage during their whole life.Additionally,only adults of Chrissia and Stenocypris species have the characters: five plus one swimming setae are present on antenna.3.Basing on the results of checklist of freshwater ostracods in China and the geographical distribution of 99 living freshwater ostracods,results are analyzed: most species are endemic species,distributing in the Central Region and the South Region;to the proportion of species,more than half species are Cyprididae species,this also happens in Oriental species;basing on JAE analysis to species except endemic species,provinces in the Northeast Region and the Qingzang Region are similar to the traditional geographical distribution in China;the Central Region,the South Region and the Southwest Region show higher similarity than others;basing on the Jaccard similarity coefficient and the systematic analysis,the Southwest Region and the Qingzang Region show higher similarity than others.