Larvae Crowding Increases Development Rate, Improves Disease Resistance, and Induces Expression of Antioxidant Enzymes and Heat Shock Proteins in Mythimna separata (Lepidoptera: Noetuidae)

Multi-Omics Reveals the Effect of Population Density on the Phenotype, Transcriptome and Metabolome of Mythimna separata

Population-density-dependent polymorphism is important in the biology of some agricultural pests. The oriental armyworm (Mythimna separata) is a lepidopteran pest (family Noctuidae). As the population density increases, its body color becomes darker, and the insect eats more and causes greater damage to crops. The molecular mechanisms underlying this phase change are not fully clear. Here, we used transcriptomic and metabolomic methods to study the effect of population density on the differentiation of second-day sixth instar M. separata larvae. The transcriptomic analysis identified 1148 differentially expressed genes (DEGs) in gregarious-type (i.e., high-population-density) armyworms compared with solitary-type (low-population-density) armyworms; 481 and 667 genes were up- and downregulated, respectively. The metabolomic analysis identified 137 differentially accumulated metabolites (DAMs), including 59 upregulated and 78 downregulated. The analysis of DEGs and DAMs showed that activation of the insulin-like signaling pathway promotes the melanization of gregarious armyworms and accelerates the decomposition of saccharides, which promotes the gregarious type to take in more food. The gregarious type is more capable of digesting and absorbing proteins and decreases energy consumption by inhibiting transcription and translation processes. The phase change traits of the armyworm are thus attributable to plasticity of its energy metabolism. These data broaden our understanding of the molecular mechanisms of insect-density-dependent polymorphism.

Larval crowding effects during early development in the Chinese oak silkmoth Antheraea pernyi (Lepidoptera: Saturniidae)

Chinese sericulture relies in part on the rearing of the Chinese oak silkmoth Antheraea pernyi, an insect with key cultural and ecological roles. While feeding primarily on oak, Antheraea species are known to accept alternative hosts such as birch Betula sp with little to no apparent negative fitness consequences. This opens up the range of hostplants that could be used for large‐scale rearing of A. pernyi for silk production and food, or used by this species in possible invasions. To date, however, the natural history and ecology of A. pernyi remain subject of investigation. For instance, we still do not know how individuals respond to crowding developmental environments, which is an important factor to consider for the ecology of the species as well as for commercial rearing. Here, I describe the implications of larval crowding to the survival and growth of A. pernyi larvae during early development. I show that higher crowding is associated with stronger negative effects on growth and survival, corroborating findings from other holometabolous insects. I then discuss the implications of this findings for our understanding of optimum larval crowding. Overall, the findings reveal important ecological information for an insect species key for provisioning and cultural ecosystem services.

Probing the antioxidant activity of functional proteins and bioactive peptides in Hermetia illucens larvae fed with food wastes

Food waste is becoming more prevalent, and managing it is one of the most important issues in terms of food safety. In this study, functional proteins and bioactive peptides produced from the enzymatic digestion of black soldier fly (Hermetia illucens L., BSF) fed with food wastes were characterized and quantified using proteomics-based analysis. The results revealed approximately 78 peptides and 57 proteins, including 40S ribosomal protein S4, 60S ribosomal protein L8, ATP synthase subunit alpha, ribosomal protein S3, Histone H2A, NADP-glutamate dehydrogenase, Fumarate hydratase, RNA helicase, Chitin binding Peritrophin-A, Lectin C-type protein, etc. were found in BSF. Furthermore, functional analysis of the proteins revealed that the 60S ribosomal protein L5 (RpL5) in BSF interacted with a variety of ribosomal proteins and played a key role in the glycolytic process (AT14039p). Higher antioxidant activity was found in peptide sequences such as GYGFGGGAGCLSMDTGAHLNR, VVPSANRAMVGIVAGGGRIDKPILK, AGLQFPVGR, GFKDQIQDVFK, and GFKDQIQDVFK. It was concluded that the bioconversion of food wastes by BSF brought about the generation of a variety of functional proteins and bioactive peptides with strong antioxidant activity. However, more studies are required to exploit BSF's potential in the value addition of food wastes.