| Brachymeria lasus(Hymenoptera:Chalcididae)is a solitary pupal parasitoid,with a host range of more than 100 species of Lepidoptera,Hymenoptera and Diptera,and have chosen to be biological control agent on a few pests.To ascertain the possibility of B.lasus as a potential parasitoid in suppressing population of Hyphantria cunea,and carried out research on propagation technique,we determined the optimum temperature range for B.lasus and as well as effective accumulated temperature and development starting temperature.Under laboratory conditions,we investigated the parasitoid offspring performance(longevity,size)and sex ratio of the offspring that emerged from hosts of different sizes.Besides,transcriptome sequencing was performed on female and male B.lasus and related genes was screened,offering theoretical basis for using this parasitoid.1.We surveyed the parasitism conditions of summer and overwintering pupae of H.cunea.Generally,four Hymenopteran parasitoid wasps(Chouioia cunea,Coccygomimus disparis,Tetrastichus nigricoxae,B.lasus)and one Dipterous parasitoid fly(Exorita japonica)successfully emerged from the pupae of H.cunea collected in the field.C.cunea had the highest parasitism ratios to both summer pupae(7.1%)and overwintering pupae(13.3%).B.lasus only parasitize summer pupae,which ratio was 6.6%.In addition,we found that eclosion ratio of H.cunea adults emerged from pupae expose to B.lasus(17.4%)was significantly lower than B.lasus absense condition(90.5%),which suggested that B.lasus had a considerable potential efficacy in controlling H.cunea.2.We examined the relationships between temperature and developmental duration from egg to adult.The results showed that wasps can successfully develop at different developmental temperatures range from 18℃to 32℃.There was a highly significant positive relationship between developmental temperature and the developmental rate from egg to adult.The development starting temperature of B.lasus was 13.20±1.73℃,and effective accumulated temperature was 210.29±28.74 day-degrees.3.We investigated the parasitoid offspring performance(longevity,size)and sex ratio of the offspring that emerged from hosts of different sizes.For H.cunea,the length of hind tibia of parasitoid which emerged from 67-milligram pupa was only 1.23mm,whose longevity was4 days,while the length of hind tibia of parasitoid which emerged from 154-milligram pupa was 2.01mm,whose longevity was 60 days.For Spodoptera exigua,the length of hind tibia of parasitoid which emerged from 49-milligram pupa was only 0.81mm,whose longevity was9days,while the length of hind tibia of parasitoid which emerged from 129-milligram pupa was 1.83mm,whose longevity was 67 days.These results showed that host size can reflect the size and longevity of the emerging offspring.More B.lasus males emerged from smaller hosts,and more females from bigger hosts,sex ratio(the percentage of female wasps)was larger from large hosts(56.25%)than those from small hosts(26.67%).Besides,body size and longevity of female was higher than that of male.4.To reveal B.lasus sex differences at the transcriptional level,we carried out an Illumina-based transcriptomic analysis.All high-quality reads(101,945,678)were pooled and assembled by using Trinity with the default parameters,and a total of 254,656 transcripts with lengths longer than 200 bp were generated.The pooled assembled unigenes were searched using blastx against 5 public databases with an E-value cutoff of 10~-55 to get annotation.A total of 37453 unigenes were successfully annotated,including 17248 genes in GO,13491 genes in COG,35427 genes in Nr,18195 genes in Swiss-Prot,and 15133 genes in KEGG.By comparing female to male transcriptomes,1416 DEGs and 12648 unbiased genes in B.lasus were found.Among these DEGs,there were 986 female biased and 430 male biased genes annotated.KEGG pathway enrichment tests revealed that DNA replication,fatty acid biosynthesis,metabolism,fatty acid synthase gene,insect hormone biosynthesis were up-regulated in females.In addition,only the phototransduction-fly pathway was enriched in males.5.Of the TRP channel genes in B.lasus,most belong to two subfamilies:TRPC and TRPA.TRPC plays an important role in the perception of light signals,i.e.,the phototransduction pathway,which was enriched in B.lasus male adults.To validate the transcriptome results,15 DEGs and 4 unbiased genes were selected for qRT-PCR verification.Generally,the trends for down-or up-regulated transcription of the DEGs by qRT-PCR analysis were consistent with those found in the transcriptome analysis,as were those of the unbiased genes,indicating the reliability of our expression profiling.As for sexual dimorphism in the phototaxis test;although both females and males tended to move towards light,male adults had significantly higher phototaxis than females. |
