Effects of different foods on growth， development and reproduction of Chrysopa pallens and comparative transcriptome analysis

Objective This study aimed to analyze the effects of different foods on the development， reproduction and transcriptomic differences of Chrysopa pallens， to screen indoor alternatives to feed Chrysopa pallens larvae， so as to provide a theoretical basis for large-scale Chrysopa pallens rearing.Method Four food types-Aphis craccivora nymphs， Sitobion avenae nymphs， 2^nd instar larvae of Spodoptera litura， 2^nd instar larvae of Spodoptera frugiperda were used to feed the 1^st， 2^nd， 3^rd instar larvae of Chrysopa pallens under indoor artificial rearing conditions to investigate the effects of different foods and rearing stages on the development and reproduction of Chrysopa pallens. The transcriptome sequen-cing was performed on the 3^rd instar larvae fed on Aphis craccivora and Spodoptera frugiperda based on effects of different foods on biological characteristics of Chrysopa pallens.Result During the three rearing stages， Chrysopa pallens larvae fed on Aphis craccivora and Sitobion avenae could develop and pupate normally. Low survival rates in pupal stage were observed among the Chrysopa pallens larvae fed on Spodoptera litura and Spodoptera frugiperda since their 1^st and 2^nd instar stages； however， for Chrysopa pallens fed on these two food types since 3^rd instar stage， the feeding effects on their development was less pronounced as most Chrysopa pallens larvae were able to pupate. For the 3^rd instar larvae of Chrysopa pallens， no significant effects of feeding on the four food types was found in their pre-oviposition period or oviposition duration of females （P>0.05）， but those fed on Aphis craccivora and Sitobion avenae enjoyed a significantly higher fecundity per female and egg hatching rates than those fed on Spodoptera litura and Spodoptera frugiperda （P<0.05）. Transcriptomic analysis revealed 680 differentially expressed genes （DEGs） between Chrysopa pallens larvae fed on Spodoptera frugiperda and those fed on Aphis craccivora， among which 333 were up-regulated and 347 were down-regulated. GO functional annotation and enrichment analysis indicated that these DEGs were primarily enriched in terms related to integral component and intrinsic component of membrane. KEGG signal pathway enrichment analysis showed that the DEGs were mainly enriched in pathways such as metabolism of xenobiotics by cytochrome P450， ascorbic acid and aldarate metabolism.Conclusion Chrysopa pallens larvae of all instar stages predate Aphis craccivora nymphs， Sitobion avenae nymphs， the 2^nd instar larvae of Spodoptera litura， and the 2^nd instar larvae of Spodoptera frugiperda. As Chrysopa pallens larvae grow with stronger adaptability to different foods， feeding on Spodoptera litura and Spodoptera frugiperda since the 3^rd instar stage brings minor effects on their growth， development and reproduction. DEGs identified between Chrysopa pallens fed on Spodoptera frugiperda and those fed on Aphis craccivora are associated with material transport， cellular immunity， and energy metabolism.