Does Insulin Signaling Regulate the Pre-migratory Phenotype Diapause in Monarch Butterflies (Danaus Plexippus)?

Abstract

In fall months, monarch butterflies (Danaus plexippus) enter a phenotypic state called diapause that is characterized by the sequestration of fat reserves and halted development of reproductive organs. This state in invertebrates such as C. elegans and C. pipiens has been shown to be regulated by the insulin signaling pathway. Using dsiRNA (interfering RNA), the genes for the insulin receptor InR, FOXO (Forkhead Transcription Factor) were targeted to test if this relationship exists in monarchs butterflies as well. Ideally mature oocytes would be counted for each treatment group for quantitative analysis. Due to an insufficient feeding protocol, quantitative data for this relationship was difficult to collect as the monarchs did not fully mature reproductively. However, photographs of the abdominal dissections and relative oocyte development reveal a potential success for future trials of this experiment with proper recalibration of the feeding protocol. It can be noticed in these photographs that InR interfered monarchs had fractionally less developed ovaries than the other treatment groups. Only one monarch butterfly had mature oocytes, and was in the FOXO treatment group, consistent with other successful experiments of this nature. If insulin signaling can be confirmed to regulate diapause, it may be key in regulating migration as whole in monarch butterflies.