New insights into aberrant sperm morphology: The structure of dimorphic spermatozoa in Edessa rufomarginata (De Geer, 1773) (Hemiptera: Pentatomidae)

Male bugs of the Pentatomidae family can produce heteromorphic sperm during spermiogenesis, forming two or more distinct morphotypes. In Edessa rufomarginata (De Geer, 1773), this phenomenon culminates in the production of two specific sperm morphotypes: one typical (Type I) and the other aberrant (Type II). Using transmission electron microscopy techniques, we describe in detail the characteristics of these cells. Typical sperm have characteristics common to Heteroptera, including an acrosome positioned anteriorly to the nucleus, which later elongates laterally to it; two symmetrical mitochondrial derivatives in a “half-moon” shape connected to the axoneme by two bridges; and the absence of accessory bodies. In contrast, aberrant spermatozoa have a rounded acrosome that does not extend laterally to the nucleus until the nucleus-flagellum transition region. Furthermore, the mitochondrial derivatives of these spermatozoa are considerably thicker, reaching up to five times the diameter observed in typical spermatozoa. However, both morphotypes exhibit the synapomorphies of Heteroptera. These structural distinctions indicate a marked morphological variation that may be associated with specific functions or reproductive strategies of the species. These new morphological data are possibly specific to the genus Edessa, or perhaps to the Edessinae. They may be complementary tools for resolving taxonomic and phylogenetic questions for this diverse group.