Anatomy of the male reproductive system and sperm morphology in the caterpillar‐hunting wasp Ancistrocerus antilope (Hymenoptera, Vespidae)

Abstract

Abstract. The male reproductive system of the caterpillar‐hunting wasp Ancistrocerus antilope was composed of the testes, seminal vesicles, accessory glands, the penis, and the connecting ducts. The testes, which were paired structures lined with a thin layer of squamous epithelium, were composed of several lobes that contain developing spermatozoa. These spermatozoa began as spermatocytes in the distal portion of the testicular lobe and, as they matured, they moved proximally toward the seminal vesicles. Upon maturation, the spermatozoa were long, thin structures with a nucleus of ∼10–15 μm in length and 1–2 μm in width. Their tails, which were not morphologically distinct from their heads at the gross level, averaged 388±25 μm in length. Once the spermatozoa had fully developed, they traveled from the testes to the seminal vesicles, where they were stored. The walls of the seminal vesicles were composed of a ciliated, pseudostratified, columnar epithelium. A layer of fibrous connective tissue termed the testicular capsule encapsulated both the testes and the seminal vesicles. Upon ejaculation, the spermatozoa moved through the deferent ducts, where they combined with granular fluid from the accessory glands. From here, they traveled via the ejaculatory duct to the penis, where they were expelled. In this study, these anatomical descriptions are discussed in reference to other species of the Hymenoptera.