Comparative spermatology in Plecoptera (Insecta): an ultrastructural investigation on four species

The ultrastructure of spermatozoa. of four Plecoptera species, Leuctra fusc a Linnaeus, Brachyptera risi (Morton), Taeniopteryx stankovitchi Ikonomov, T. kuehtreiberi (Aubert), was investigated by light microscopy, scanning an d transmission electron microscopy, and immunofluorescence microscopy. The spermatozoa of all the species have a complex acrosome, are filiform and fl agellate, with a '9 + 9 + 2' axoneme flanked by two mitochondrial derivativ es. However, the structure shows a certain interspecific heterogeneity. L. fusca has a short conical nucleus in the apical position and an axoneme fla nked by two accessory bodies. In the sperm of the Taeniopterygidae, the nuc leus is a long cylindrical body which lies between the two mitochondrial de rivatives flanking the axoneme for most of its length. Our results suggest a close phylogenetic affinity between Plecoptera and the other orders of Po lyneoptera, although the proposed sister-group relationship between Plecopt era and Embioptera. cannot be confirmed. (C) 2001 Elsevier Science Ltd. All rights reserved.