Nutritional Requirements And Artificial Diet Formulation Of Tetranychus Urticae

Although being an important pest,Tetranychus urticae is also an important prey used in production of specialist predatory mites.This species fed on thousands of host plants and showed strong capability in host adaptation,but no success artificial diet has been developed for it.In this study,we compared adult longevity and reproduction of T.urticae that fed on its natural food(bean leaves)and an artificial diet with leaf juice added,and tried to investigate the reason why the artificial diet was inefficient through transcriptome analyses.We studied the differences of protein,fat,saccharides,amino acids,vitamins and trace elements between fresh bean leaves and fresh bean leaf juice.Among 10 essential amino acids,8 had their contents significantly lower in leaf juice than in leaves,with content of lysine decreased the most(38.46%).Among 8 non-essential amino acids,7 had their contents significantly lower in leaf juice than in leaves,with content of cysteine decreased the most(66.67%).The vitamin B1 content was lower than limit of quantification(0.10mg/100g),so it’s not detected in leaf juice.The contents of vitamin E,B2,B6,B12 and nicotinic acid were 45.00%,27.78%,34.30%,56.79%,27.43% lower in leaf juice than in leaves,respectively.But the content of vitamin K1 increased by 18.18% in the juice.K,Mg and Mn concentrations were 12.25%,15.60%,27.33% lower in leaf juice than in leaves,respectively.Artificial diets for T.urticae were prepared through adding egg yolk,honey,amino acids and other nutrients to bean leaf juices.We have tried a total of 33 recipes.The best formula was selected: sucrose8 g,fresh yolk 25.00 g,compound vitamin 0.08 g,potassium dihydrogen phosphate 0.15 g,streptomycin sulfate 0.005 g,potassium sorbate 0.20 g,fresh bean leaf juice 164.00 ml.We compared adult longevity and reproduction of T.urticae that fed on its natural food(bean leaves)and this artificial diet.The results showed that the average adult life span and cumulative reproductive rate of T.urticae decreased by 53.40% and 93.80%,respectively.The fecundity of artificial feed was very low,only a few female adults lay eggs for more than a week,indicates that artificial diet only allows female adult mites lay some eggs for their nutritional needs.To explore the reasons for inefficiency of the artificial diet,transcriptome sequences of female adults fed on natural host bean leaves,on artificial diet,and starved individuals were compared.There were 1731 differentially expressed genes in total,most of which(77.10%)were down-regulated when comparing those fed on artificial diet and natural food.When T.urticae was fed with the artificial diet,the differentially expressed genes were mainly concentrated in the biological processes related to digestion,especially in the pathways related to lipid metabolism,and most of them were down-regulated.Our results indicated the significance in further investigating lipid demand and metabolism of T.urticae to improve its mass rearing techniques.