Ecological Studies On Gamasid Mites On Three Species Of Wild Rodents(Apodemus Chevrieri,Mus Pahari And Niviventer Confucianus) In Yunnan Province,Southwest China

Objective:This study is to comprehensively and systematically understand the infestation,distribution and related ecological issues of gamasid mites on the body surface of three species of wild rodents(rats and mice),the Chevrier’s field mouse(Apodemus chevrieri),Gairdner’s shrew mouse(Mus pahari)and Chinese white-bellied rat(Niviventer confucianus),in Yunnan province of southwest China.Methods:Based on the original data from a long-term accumulated field investigation in39 counties of Yunnan province,southwest China between 1990 and 2015,a series of statistical methods were used to analyze the infestation,distribution and related ecological issues of gamasid mites on the body surface of three species of wild rodents(rats and mice),A.chevrieri,M.pahari and N.confucianus.The constituent ratio(Cr),prevalence(P),mean abundance(MA)and mean intensity(MI)were conventionally used to describe the infestations of gamasid mites on the wild rodents.The linear relationships were then analyzed between the prevalence(P)and mean abundance(MA).Sorensen’s similarity index was used to measure the species similarity of gamasid mites on the male and female rodent hosts.The infestation differences on different sexes and ages of the hosts were compared and the altitude influence on the parasitisim of gamasid mites were analyzed.An epidemiological model was used to calculate the predicted prevalence(PP)through the mean abundance(MA),and the linear relationship was then analyzed between the observed prevalence(OP)and predicted prevalence(PP).Taylor’s power function model was used to measure the spatial distribution patterns of dominant gamasid mites among different individuals of the rodent hosts.Preston’s lognormal model was used to fit the species abundance distribution of gamasid mite communities on three species of wild rodents.The total species of gamasid mites were estimated based on the fittings of species abundance.Results:A total of 3209 individuals of three species of wild rodents(A.chevrieri,M.pahari and N.confucianus)were captured from 39 counties of Yunnan province.From the body surface of the wild rodents,26460 individual gamasid mites were collected and identified as 70 species of 20 genera in 8 families.Of the 39 investigated counties,a total of1910 Chevrier’s field mice(A.chevrieri)were captured from 15 counties,and 4035 gamasid mites were collected from 1910 mice,which were identified as 50 species of 18 genera in 7families.Of the identified 50 species of gamasid mites,there were two dominant mite species on the mouse A.chevrieri with the highest constituent ratio(Cr).These two dominant species of gamasid mites were Eulaelaps shanghaiensis(Cr=18.94%)and E.substabularis(Cr=14.33%).The species similarity of gamasid mites reached 80.95%(Css=80.95%)between the male and female Chevrier’s field mice(A.chevrieri).The prevalence and mean abundance of the mite E.shanghaiensis on the adult mice were higher than those on the juvenile mice(P<0.05).A total of 720 Gairdner’s shrew mice(M.pahari)were captured from14 counties of Yunnan province.The 14257 gamasid mites collected from the 720 mice were identified to be 37 species of 12 genera in 2 families.Of the identified 37 species of gamasid mites on M.pahari mice,three species were the dominant gamsid mites with the highest constituent ratio(Cr),and these three dominant mite species were Laelaps guizhouensis(Cr=75.33%),L.paucisetosa(Cr=14.68%)and L.xingyiensis(Cr=6.91%).The species similarity of gamasid mites between the male and female Gairdner’s shrew mice reached75.86%(Css=75.86%).The prevalence of L.paucisetosa on the male mice was higher than that on the female mice(P<0.05).The mean abundance of L.guizhouensis on the female mice,however,was higher than that on the male mice(P<0.05).The prevalence and mean abundance of two dominant mite species(L.guizhouensis and L.paucisetosa)on the adult mice were higher than those on the juvenile mice(P<0.05).A total of 579 Chinese white-bellied rats(N.confucianus)were captured from 21 counties of Yunnan province.The collected 8168 gamasid mites from the 579 rats were identified to be 43 species of 15genera in 5 families.Of the identified 43 species of gamasid mites on N.confucianus rats,four species were the dominant gamsid mites with the highest constituent ratios(Cr),and these four dominant mite species were L.turkestanicus(Cr=43.91%),L.echidninus(Cr=18.72%),L.fukienensis(Cr=16.99%)and L.traubi(Cr=16.31%).The species similarity of gamasid mites between the male and female Chinese white-bellied rats reached 71.64%(Css=71.64%).The prevalence and mean abundance of L.turkestanicus on the male rats was higher than that on the female rats(P<0.05).The mean intensity of L.echidninus on the male rats was also higher than that on the female rats(P<0.05).The infestation differences of four dominant mite species(L.turkestanicus,L.echidninus,L.fukienensis and L.traubi)on the adult rats and juvenile rats were of no statistical significance.All the dominant gamasid mites on the three species of wild rodents showed an aggregated distribution pattern among different individuals of the corresponding host animals.A high correlation also existed between the prevalence(P)and mean abundance(MA)in some dominant gamasid mites.For example,the correlation coefficient(r)between P and MA in L.paucisetosa and L.xingyiensis reached 0.892 and 0.955(P<0.05)on M.pahari mice,and the correlation coefficient(r)between P and MA in L.turkestanicus,L.echidninus and L.fukienensis reached 0.916,0.976and 0.979(P<0.05)on N.confucianus rats.With the help of an epidemiological model,the predicted prevalence(PP)were calculated from the mean abundance(MA)for some dominant gamasid species.There was a high correlation between the observed prevalence(OP)and the predicted prevalence(PP)with a better fitting goodness(EF value was close to 1).For example a positive linear correlation existed between OP and PP in L.paucisetosa and L.xingyiensis on the mouse M.pahari(r=0.946 and 0.916,P<0.05;EF=0.991 and 0.984).There was also a positive linear correlation between OP and PP in four dominant species of gamasid mites,L.turkestanicus,L.echidninus,L.fukienensis and L.traubi on the rat N.confucianus(r=0.964,0.956,0.99 and 0.967,P<0.05;EF=0.8827,0.8116,0.5791 and0.7356).The species abundance distribution of gamasid mite communities on three species of wild rodents(rats and mice),A.chevrieri,M.pahari and N.confucianus,conformed to lognormal distribution,and a better fitting effect was obtained by using Preston’s lognormal model(R~2=0.08715,0.7370 and 0.6219).On the basis of fitting the theoretical curve of species abundance,the total species of gamasid mites were estimated by roughly calculating the area under the curve.For example the total species of gamasid mites on A.chevrieri mice was estimated to be 71 species and there were 21 rare species with very few individuals missed in the sampling field investigations.Conclusions:There are abundant species of gamasid mites on three species of wild rodents,Apodemus chevrieri,Mus pahari and Niviventer confucianus.The most important dominant mite species on the rodents are E.shanghaiensis,L.guizhouensis and L.turkestanicus respectively.The prevalence is highly correlated with mean abundance in some dominant mites.The mite infestations on male and adult rodents are usually higher than those on the females and juveniles.The mite infestations among different individuals of the same rodent species are very uneven,presenting as an aggregated distribution.The predicted prevalence(PP)can be calculated by means of mean abundance(MA).The species abundance distributions of gamasid mites on the three species of wild rodents conform to lognormal distribution.Based on fitting the species abundance,the total mite species can be predicted.