A comparative study of vitellogenesis across Culicoides sonorensis and Stomoxys calcitrans

In hematophagous dipterans, vitellogenesis is tightly linked to blood feeding, as the blood meal serves as the initial catalyst for the succession of egg development. While numerous reports have characterized this process in mosquitoes, there are limited studies in vectors of veterinary importance, such as Culicoides sonorensis midges and Stomoxys calcitrans stable flies. By taking a comparative physiology approach, we used immunohistochemistry and RT-qPCR to characterize follicular development into the five Christopher’s stages and determine putative vitellogenin orthologs in C. sonorensis and S. calcitrans females. While five Christophers’ stages were observed in both species, the timing and nutritional requirements of follicular development were dissimilar. In midges, follicular development arrested at Stage II until blood feeding. After blood feeding, each follicle increased in size as the oocyte developed, and completed the remaining stages by 48 h post blood meal. In contrast, stable flies required multiple blood meals to complete egg development, with follicular development arresting at each stage until the next blood meal stimulated progression to the subsequent stage. Furthermore, while putative vitellogenin orthologs were analyzed, putative ortholog number and expression differed between and within species, respectively. These data illustrate the complexity of vitellogenesis regulation across species and serve as a foundation for future work to understand the underlying mechanisms of vitellogenesis in these understudied vectors.