Physiology And Biochemical Responses Of The Cotton Bollworm To Ultrasound And Molecular Basis For Its Auditory System

The cotton bollworm,Helicoverpa armigera(H(u|¨)bner)(Lepidoptera:Noctuidae) is a videspread polyphagous pest using more than 60 crops as host plants and has high mobility and fecundity.Like other noctuid moths,H.armigera has tympanal ears on the lateroposterior edge of the metathoracic segment,which can detect the echolocation calls of insectivorous bats and have an auditory best frequency at 15-30 kHz with high sensitivity.The male and female of H.armigera are both able to produce ultrasonic signals in the range of 20-40 kHz while flying.In the present study,in order to know that the mechanism of H.armigera hearing,effects of ultrasound from a commercial device, LHC20,on fecundity of adults and development of larvae H.armigera were investigated in laboratory.And Changes in the activities of acetylcholinesterase(ACHE),superoxide dismutase(SOD),catalase(CAT),and peroxidase(POD) were measured in H.armigera after ultrasound stress.And H.armigera Nan and Iav genes were cloned and sequenced. The major results are summarized as following:1.Physiological effects of ultrasound on H.armigeraThe number of eggs laid by females of H.armigera in the absence and presence of ultrasound increased gradually with adult age up to 4 days,and then decreased gradually over the next 6 days.Females exposed to ultrasound from the LHC20 device laid most of their eggs between the third and sixth day,whereas those in the control treatment did between the third and seventh day.Ultrasound from devices significantly increased the number of eggs laid by H.armigera.The number of eggs laid by females was increased by 54.5%when exposed to ultrasound from the LHC20 device,respectively,compared to the control treatment.Viability of eggs laid by females in the control treatment was 61.51%,but those exposed to ultrasound from the LHC20 device was 67.64%.However, this difference was not significant.Across all three tests,each female,on an average,had 1.43 spermatophores in the presence of ultrasound and 1.28 spermatophores in the absence of ultrasound.This difference was significant.The weight per larva in separate test containers with ultrasound was not significantly than the weight per larva in separate test containers without ultrasound.The larva of H. armigera in the absence and presence of ultrasound had the similar daily development pattern.The pupation rate in separate test containers with ultrasound was significantly than the pupation rate in separate test containers without ultrasound.The eclosion rate in plastic containers with ultrasound was not significantly than the eclosion rate in plastic containers without ultrasound.2.Effect of ultrasound on acetylcholinesterase activity in H.armigeraThe AChE activities were significantly elevated compared with the control,after exposure to ultrasound stress for 6 h or 12 h.The maximum AChE activity was 0.434 U/mg prot after 12 h ultrasound stress exposure,and was about 2.6-fold the control.The activity of AChE was only 0.291 U/mg prot after 24 h ultrasound stress exposure,a total increase of 16%.The results of the ultrasounds with different lengths of time have significant but different effects on acetylcholinesterase activities in different developmental stages of H. armigera.The enzyme activities were increased in 20 min ultrasound-stress groups in adults,and decreased in 30 and 50 min groups in pupa,whereas they were reduced in 20 min groups and enhanced in 40 and 60 min groups significantly in larvae.3.Effect of ultrasound on the activity of antioxidant enzymes in H.armigeraThe SOD activities did not change significantly compared with the control after ultrasound exposure for different lengths of time,and they were between 94%and 106% of the control value.The ultrasound stress induced change in CAT activity related to the different durations.The CAT activity increase significantly at 6 h and 12 h ultrasound stress exposure,and the activity of CAT was about 2.2- and 1.4-fold the control, respectively.However,the CAT activity was significantly declined under 24 h ultrasound stress exposure,and it was only 68%of the control value.The increase was statistically significant under 6 h and 12 h ultrasound stress exposure,and the activities of POD both were 1.2-fold the control value.No significant change in POD activity was observed at 24 h of ultrasound stress exposure,and the POD activity was 98%of the control value.In adult,the activities of SOD and CAT changed irregularly but not significantly compared with the control after ultrasound exposure.However,the SOD and CAT activities declined after ultrasound exposure in larvae,and the SOD activity increased after ultrasound exposure in pupae.A significant increase in POD activity in adult H. armigera was observed at 40 min ultrasound exposure.And the POD activity in larvae H. armigera increased significantly after 20 min,30 min,40 min,and 50 min ultrasound exposed,respectively.4.Cloning and sequence of cDNA of Nanchung gene from H.armigeraThe cDNA of Nan gene was cloned from black porgy ovary by means of reverse transcriptase and polymerase chain reaction(RT-PCR) and 5' and 3'-rapid amplification of cDNA ends(RACE) analyses.The cDNA is 1020 bp in length and encodes a putative protein of 339 amino acids(m.w.39.191 kD,pI 6.76).The comparison of Nan amino acid sequence with those of nearly of all the other known members of insects showed that Bombyx mori shared the highest identity with H.armigera.5.Cloning and sequence of cDNA of Inactive gene from H.armigeraThe cDNA of Iav gene was cloned from black porgy ovary by means of reverse transcriptase and polymerase chain reaction(RT-PCR) and 5' and 3'-rapid amplification of cDNA ends(RACE) analyses.The cDNA is 1209 bp in length and encodes a putative protein of 402 amino acids(m.w.45.132 kD,pI 6.65).The comparison of Nan amino acid sequence with those of nearly of all the other known members of insects showed that Bombyx mori shared the highest identity with H.armigera.