The Spermatozoon of Arthropoda. XXVI. The spermatozoon of Isoptera, Embioptera and Dermaptera

The spermatozoon of Reticulitermes and Calotermes appear highly evolved, and at the same time simplified. Both sperm types are devoid of acrosome. The role of the Golgi apparatus seems to be exclusively for the elaboration of the plasma membrane of mature sperms. The mitochondria are few and round, and have cristae of conventional type. The flagellum is absent. Even in the mature sperm, 2 centrioles are found, but no flagellar structures appear. No other structures are to be seen in substitution for the flagellum in Reticulitermes, while the mature sperm of Calotermes has retained a manchette of perinuclear microtubules projected outwards inside the characteristics festoons of the plasma membrane. characteristic might be interpreted as substitutes for the flagellum. In Calotermes lysosomes appear to digest large areas of the cytoplasm. The study of the sperm of Embioptera and Dermaptera demonstrates that the typical orthopteroid sperm type resembles the sperm type of most pterygota insects in having a 3 layered acrosome complex, a fusiform nucleus, a large centriole adjunct, 2 mitochondrial derivatives partly or entirely full of crystalline material and a 9 + 9 + 2 axoneme. In single lines of evolution within the orthopteroid orders this sperm type is simplified: the acrosome layers are fewer (Embioptera, Phasmida, Termites), the mitochondria also fewer or missing (Termites, Phasmida) and the flagellum is lacking (Termites).