| Chrysomya megacephala（Fabricius）is widely distributed in the zoogeographic areas of neotropical,nearctic and palaearctic regions and is widely distributed across China.It is characterized by necrophagy and coprophagy,which are regularly found around rural latrine,manure piles of livestock and poultry,and carrion.The necrophagy trait of C.megacephala raise attention from entomologists,environmental protect researchers and enterprises,aiming that its coprophagous nature can be applied to transform human feces,manure from livestock and poultry and other organic waste.However,the relative fundamental researches are a sort of lack,such as how adult C.megacephala locate manure,what is the efficiency and the mechanism of using larva C.megacephala to transform manure.These questions are short of base data which further impeded application of using C.megacephala to transform manure.It is a serious problem for China to manage swine manure.Therefore,swine manure was studied in this research with specific focus on the location,efficiency,ecological effects and further mechanisms of using C.megacephala to transform manure.With these results the theoretical basis of using insects to transform organic waste shall be supplemented and provide scientific instruction on application of C.megacephala in manure bioconversion.The main results are as follows.1 Oviposition location of C.megacephala to swine manureThis studied found that C.megacephala turned to swine manure for oviposition and its female antenna had EAG response to volatile matter of swine manure.Forty-one and33 kinds of volatile organic chemicals（VOCs）were identified from the n-hexane and headspace absorption extracts by gas chromatography-mass spectrometry（GC-MS）.Among these chemicals,3-methylindole（skatole）,phenol and 3-methylphenol were important constituents in the headspace absorption extracts.In total,30 odorant-binding proteins（OBPs）,4 chemosensory proteins（CSPs）and 2 Ammonia/ammonium transporter（AMTs）were identified from C.megacephala transcriptome.The candidate OBPs and CSPs had typical cysteine conserved sites and AMTs were comparatively high conservative in amino acid composition.Housekeeping gene EF1 was found to be the most stable reference genes in the tissues of adults.With EF1 as reference gene,the results of relative quantitative PCR showed that OBP1,OBP2,OBP3,OBP4,OBP5 and OBP6;CSP1,CSP2 and CSP3;ATM1 and ATM2 were expressed higher in the antennae,legs and wings than in the thorax and abdomen.These special organic compounds and volatile matters,highly-expressed olfactory gene in sensory tissues played a role in the location of C.megacephala to swine manure for oviposition.These specific organic compounds and VOCs from swine and highly expressed olfactory genes in sensory should have a function in the swine manure location of C.megacephala.2 Efficiency and ecological effect of swine manure conversion by C.megacephalaC.megacephala can transform swine manure with a high efficiency by small sacle trials.Under laboratory conditions,C.megacephala-transformed swine manure had an average loss of 37%-52%in fresh weight and lose of 49%-61%in dry matter compared with raw manure,and 3-12 kilo gram of fresh larvae were produced from per ton of swine manure.C.megacephala-transformed swine manure had a significantly lower water content and turned to granulation.Fertility parameter total nitrogen（TN）,total phosphorus（TP）and total potassium（TK）were 2.0%,4.7%and 1.3%,respectively,which is better than the standard of organic fertilizer.Bacterial diversity analysis and quantitative PCR indicated that the microbial structure changed significantly,and the content of salmonella sp.decreased sharply in the swine manure after C.megacephala conversion;BCR results indicated that the stability of lead,cadmium and chromium was maintained which means C.megacephala conversion did not increase the bio-availability（toxicity）of manure.Moreover,the toxicity of Cd was decreased after transformation.during C.megacephala-composting of manure significantly reduced the emission rate of CH4 and N2O in comparing with natural stacking situation.The composition and content of the VOCs changed significantly.Harmful benzene series phenol,3-methyl-phenol and1,2,4,5-tetramethyl-benzene decreased significantly.3 Influence of swine manure on larva survival and body weight in C.megacephalaLarvae fed by swine manure had a higher survival rate and better survival performance than cow manure and chicken manure.100-200 larvae should be applied to200 gram of swine manure for possible fine conversion.Larvae fed by swine manure and control feedstuff（A moist mixture of wheat bran and fish meal）had no significant difference in daily body weight,indicating that C.megacephala larvae had a good adaptation to swine manure and should be suitable for swine manure conversion.4 Mechanisms of swine manure conversion by C.megacephalaThe digestive enzymes and the gut microbes contribute to the bioconversion of swine manure in the alimentary tract of C.megacephala larvae.The alimentary tract of C.megacephala presented a distinct acid and alkali regions.The larvae had a high level of enzyme activity when bio-convert manure.The average level of protease for the first three days are 1.97,1.65 and 1.05 mg/mL,respectively;the activity of amylase were 0.53,0.50and 0.55 U/mgprot,respectively;the activity of lipase were 4.41,3.86 and 2.63 U/mgprot,respectively;the activity cellulase of were 0.27,1.73 and 1.69 U/mgprot,respectively.Larvae had highest microbial diversity and the composition and community structure of the microbial community significantly differed from 1-d-larvae to 5-d-larvae.Alphaproteobacteria,Bacilli,Bacteroidia,Betaproteobacteria,Flavobacteriia and Gammaproteobacteria were the most dominant classes in C.megacephala across life stages at class level.Microbiota changes might be be involved in heavy metal fractions,especially in Pseudomonas and Prevotella.Betaproteobacteria,Methanogens,Methanomassiliicoccaceae and Methanobrevibacter might be involved in the emissions of N2O and CH4.Comamonas sp.,Pseudomonas sp.and Aerococcus sp.might play a role in biodegradation of toxic gaseous benzene series.In this study,VOCs and olfactory genes were identified from swine manure and C.megacephala,respectively to establish the molecular basis of swine manure location in C.megacephala;the efficiency and ecological effect of using C.megacephala to transform swine manure were evaluated;the influence of swine manure on larva survival and body weight in C.megacephala,the acid-base property of different regions of digestive tract,the activity of digestive enzyme and the role of microbes were addressed to analyse the mechanisms of C.megacephala to transform swine manure.These results would accumulate basic data for basic theories on the location and transformation of swine manure by coprophagous insects,also have some guidance significance as C.megacephala to transform swine manure were in practical. |
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