The Comparison of Juvenile Hormone and Transcriptional Changes between Three Different Juvenile Hormone Analogs Insecticides on Honey Bee Worker Larval’s Development

Juvenile hormones (JHs) play a crucial role in the development of honey bee (Apis mellifera) worker larvae. Juvenile hormone analogs (JHAs), insecticides widely used in pest control, have been reported to affect the health and survival of honey bee worker larvae. However, the molecular mechanisms of JHAs in the honey bee remain unclear. In this study, we treated honey bee worker larvae with pyriproxyfen, fenoxycarb, and methoprene, three different JHAs. We monitored the changes in the transcription of genes encoding major JH response enzymes (CYP15A1, CYP6AS5, JHAMT, and CHT1) using RT-qPCR and analyzed the transcriptome changes in worker larvae under JHA stress using RNA-seq. We found that the enrichment pathways differed among the treatment groups, but the classification of each pathway was generally the same, and fenoxycarb affected more genes and more pathways than did the other two JHAs. Notably, treatment with different JHAs in the honey bee changed the JH titers in the insect to various extents. These results represent the first assessment of the effects of three different JHAs on honey bee larvae and provide a new perspective and molecular basis for the research of JH regulation and JHA toxicity in the honey bee.

Methoprene, a juvenile hormone analogue, modifies maturation and emergence in overwintering Osmia rufa L. adults

The development of methods aimed at activation of imagos at any point of wintering provides a compelling potential avenue to utilize bees for pollination of greenhouse crops during autumn, winter, and early spring. In this study, we tested methoprene, a juvenile hormone (JH) analogue as a chemical stimulant to end a diapause of Osmia rufa L. and enable bee activation and emergence under experimental conditions. The application of methoprene significantly reduced the emergence time of adult bees in winter months as compared to vehicle (acetone) and negative controls. Bees treated with methoprene started to emerge 3–6 days earlier than bees from acetone and control groups and finished emergence 2–6 days earlier too. Statistically significant differences were observed between methoprene and controls groups of male and female in all tested incubation periods. It was also observed that the effects of methoprene were significantly more effective in female specimens during the first 2 months of winter. Moreover, in females, methoprene improved reproductive traits such as an increase in the size of terminal oocytes. Similarly, in males, methoprene treatment resulted in a significant increase in a seminal vesicle size and dynamic elevation of spermatozoa number. Taken together, our results indicate that methoprene may play an important role in the termination of diapause, bee activation, and emergence.