Sperm ultrastructure in two species of Panorpa and one Bittacus (Mecoptera)

The sperm ultrastructure of the scorpionflies Panorpa liui and P. longihypovalva in Panorpidae and the hangingfly Bittacus planus in Bittacidae were investigated using transmission electron microscopy. The common features of the spermatozoa shared by all the mecopterans examined include a bilayered acrosome with a central perforatorium, an elongated homogeneously condensed nucleus, and a long flagellum with a 9+2 axoneme pattern and two mitochondrial derivatives. The two species of Panorpa possess a fossa at the posterior end of the nucleus, and differ from B. planus by lacking both the globular units running laterally from the head to the flagellum and the Golgi complex-derived membrane present in the flagellum. P. liui has pear-shaped mitochondrial derivatives and two small accessory bodies, while P. longihypovalva has elliptical mitochondrial derivatives and only one accessory body. The marked differences of the sperm structure among the Panorpa examined further confirm the paraphyly of this genus.