Morphology of the male reproductive system and sperm in Enchenopa squamigera (Linné, 1758) (Membracini) and Calloconophora argentipennis Dietrich, 1991 (Aconophorini) (Hemiptera: Membracidae).

Research on the morphology of the reproductive system and sperm has provided valuable insights into taxonomy, systematics, and reproductive biology across diverse insect groups. Nevertheless, such investigations remain scarce for the Membracidae (treehoppers), despite the family's ecological and evolutionary significance. Here, based on light microscopy, we provide the first detailed description of the male reproductive system and spermatozoal morphology in two representative species of Membracidae: Enchenopa squamigera (Membracini) and Calloconophora argentipennis (Aconophorini). In both species, the male reproductive system conforms to the general pattern observed in other Membracoidea. It comprises a pair of testes, two vasa deferentia, each bearing a dilated region that forms the seminal vesicles, two accessory glands, and an ejaculatory duct. However, the volume and morphology of the seminal vesicles, accessory glands, and testicular follicles vary between species. The most conspicuous difference lies in follicle number, with E. squamigera possessing eight follicles per testis and C. argentipennis fourteen. In both taxa, spermatozoa occur in bundles within the seminal vesicles. In E. squamigera, the bundles exhibit a close association between the sperm head region and the epithelial lining of the vesicles. Sperm length also differs markedly, measuring 226 µm in E. squamigera and 102 µm in C. argentipennis. Additionally, spermatozoa of both species possess a branched terminal region of the flagellum, with terminal filaments measuring 77 µm and 1.9 µm, respectively, a distinctive feature previously reported only in cicadellids and membracids. Overall, we discuss how differences in the number and dimensions of follicles, and in sperm length, may reflect distinct evolutionary trajectories and potentially divergent reproductive strategies within the family Membracidae.