Comparative Transcriptome Analysis of the Effects of a Non-Insect Artificial Diet on the Nutritional Development of Harmonia axyridis

Simple SummaryTheHarmonia axyridisis an important natural enemy insect that has received widespread attention in research and the application of biological pest control. Currently, suitable artificial feed for the mass-rearing of theH. axyridishas not been found, which affects the application of this natural enemy in biological control. This study found that the egg production of artificial feed without added egg yolk is similar to that of artificial feed without added egg yolk supplemented with juvenile hormone III. Compared to the control artificial feed, the egg production significantly increased, which is of great significance for further exploring the effects of non-insect source artificial feed on the growth and development of theH. axyridis.Artificial diets applied in the mass-rearing propagation ofH. axyridiscan improve reproductive ability by optimizing the feeding formula. This study used transcriptome data to investigate the effects of various artificial diets on the growth and development ofH. axyridis. Results indicate that spawning increased with the low-fat and JH III-supplemented artificial diet (Diet 3). Furthermore, the highest glycogen content found in Diet 3 was significantly different from the other two groups. Triglyceride content decreased as adult feeding time increased in the three artificial diet groups, with the fastest decrease observed in the low-fat diet (Diet 2). Protein content increased gradually in the high-fat diet (Diet 1) group compared to the other treatment groups. The adults reared on low-fat artificial diets, when compared to those on artificial diets supplemented with juvenile hormones at the transcriptome level, were found to have upregulated genes enriched in ubiquitin-mediated proteolysis, ribosome biogenesis, and the hedgehog signaling pathway. In contrast, the genes upregulated in the latter group were enriched in oxidative phosphorylation, amino acid biosynthesis, and the metabolism of other amino acids. The results suggest that nutritional status significantly affects the growth and development ofH. axyridisand has practical implications for the artificial feeding of natural pest enemies.