Comparative Analysis And Adaptive Evolution Of Morphology And Mitogenomes In Different Flight Ability Grasshoppers

Fifty-one species of grasshoppers belonging to 8 families were photographed by Micro-CT instrument.The 3D images of 51 male and 44 female individuals were obtained.The wing length,body length,total volume,dorsal longitudinal muscle volume and hind femur volume of all grasshoppers were measured and compared.At the same time,the mitochondrial DNA data of 80 species of grasshoppers on Genebank and one species of grasshoppers were sequenced in this study,and the adaptive evolution of grasshoppers in flight ability was preliminarily discussed.The conclusions are as follows:1.The largest muscle related to flight ability in grasshoppers is the dorsal longitudinal muscle,which exists independently in the center of the mesothorax.The dorsal longitudinal muscle volume determines the ability of grasshoppers to shake their wings,in the other way,it can make wings to beat and provide lift for flight.And the grasshoppers which have no wings or short wings do not have flight ability neither have the dorsal longitudinal muscle;most of the flying grasshoppers have the dorsal longitudinal muscle.In all of 48 spcieces of grasshoppers,which have the strongestdorsal longitudinal muscle is Thrinchus schrenkii from Pamphagidae,whose dorsal longitudinal muscle volume accounts for 1.78% of the total volume.2.The ratio of hind femur volume and total volume represents the development of jumping ability.Among 48 species of grasshoppers with hind feet,the proportion of hind femur volume to total volume is between 2.1% and 19.6%.The grasshoppers were divided into two groups: those with dorsal longitudinal muscle and those without dorsal longitudinal muscle.There was a significant difference in relative wing length between the two groups,and thehind femur volume/total volume was not significant.It proved that jumping ability was not directly related to flight ability.3.Comparing the data of all females with that of males,we know that females have shorter wings than males.Several species of grasshoppers have long wings,and females become short wings.However,the degree of muscle development was significantly higher than that of males.4.By Ka/Ks analysis of 13 coding proteins of mitochondrial DNA of 30 grasshoppers which have been photographed in 3-D images,30 grasshoppers were divided into two groups: nondorsal longitudinal muscle/dorsal longitudinal muscle group and higherhind femur volume/lower hind femur volume group,knowing that the Ks value of both groups is higher in the underdeveloped muscle group,it proves that the underdeveloped muscle group has smaller population and more genetic drift,so the synonymous mutation rate is higher.5.Through the comprehensive analysis of Ks,Ka and Ka/Ks,we know that the genes affecting flight ability are nd4 l and nd6,among which the Ka/Ks value of nd6 gene is negatively correlated with the dorsal longitudinal muscle volume/total volume.That is to say,with the volume increasing,the Ka/Ks value of nd6 decreases.At the same time,nd2,nd4,nd4 l and nd6 are the genes affecting the development of hind femur volume/total volume.Only nd4 l and nd6 are negatively correlated with the development of hind femur volume/total volume.The results showed that the genes nd4 l and nd6 were highly correlated with grasshopper motility.6.80 grasshoppers with mitochondrial DNA data were divided into two groups,non-flying group and flying group.The total length of mitochondrial genome of the two groups was significantly different.The total length of mitochondrial genome of the non-flying group was 1497bp-15932 bp,and that of the flying group was 15443-16259 bp.And the AT-rich regions have significant differences in both length and AT content.The average length of AT-rich area in non-flying group was shorter than that in flying group,and AT content was lower.7.Comparing the Ka and Ks values of 13 protein-coding genes in each grasshopper of 80 species,the Ka/Ks values of nd2,atp8,cox3,nd3,nd5,nd4 and nd1 genes in non-flying group were lower than those in flying group,while the Ka/Ks values of cox 2,nd4 l and nd6 genes were higher.The results were consistent with the Ka/Ks analysis of 30 grasshoppers.The difference of evolution rate between nd4 l and nd6 genes was mainly determined by the difference of Ka.It indicated that nd4 l and nd6 allow more mutations in the non-flying group when the natural mutation rate was equal.