Sperm structure of some Neuroptera and phylogenetic considerations

Abstract

Spermatozoa from members of Hemerobiidae, Chrysopidae and Mantispidae (Arthropoda; Hexapoda: Neuroptera) have been examined by electron microscopy. In all species examined, the nucleus is surrounded by a nuclear envelope that in its anterior domain, fans out laterally into one (Chrysopidae) or two wings (Hemerobiidae and Mantispidae). Furthermore, the anterior sperm region is surrounded by external dense material. In Mantispidae, sperm dimorphism with two types of spermatozoa is also confirmed: paraspermatozoa (not fertilizing), provided with giant axoneme and mitochondrial derivatives, and euspermatozoa (fertilizing). Spermatozoa of Chrysopidae and Mantispidae are characterized by the lack of an acrosome while sperm cells of Hemerobiidae are provided with a bilayered acrosome. Spermatozoa from all the investigated species have axonemes of the conventional insect type, with a 9+9+2 microtubular pattern and with accessory tubules provided with 16 protofilaments. In all the examined taxa the intertubular material has the same localization also observed in all other previously analysed Neuroptera. The mitochondrial derivatives and the accessory bodies in the three families are also described. Hemerobiidae are characterized by the presence of a large groove of the plasma membrane along the right side of the anterior sperm region, which results in an eccentric position of the axoneme. Chrysopidae have large mitochondrial derivatives, which encircle the axoneme. The peculiar feature regarding the nuclear envelope was not seen in other members of neuropteroid insects. These data are discussed in the light of the phylogenetic relationships of the taxa examined.

Sperm Ultrastructure of corydalid Corydalus diasi Navás (Megaloptera, Neuropterida, Insecta) with phylogenetic considerations

“…This ultrastrastructural study of the spermatozoa of Corydalus diasi confirms the features described previously for Sialidae (Afzelius & Dallai, 1988), Raphidioptera (Afzelius & Dallai, 1988) and several Neuroptera families (Afzelius & Dallai, 1979;Zizzari, Lupetti, Mencarelli, & Dallai, 2008;Zizzari et al, 2011Zizzari et al, , 2010 (Table 1).…”

The evolution of insect sperm − an unusual character system in a megadiverse group

“…) and Dichochrysa (Neuroptera, present in Hemerobius ) (Zizzari et al. ). Placement of the acrosome vesicle: (0) surrounding the tip of the sperm anterior pole; (1) adapted to a cavity of the nucleus; (2) extending alongside the length of the nucleus; (3) extending alongside the entire length of the sperm. An acrosome shaped to fit into a cavity of the nucleus is described for Embioptera (Dallai et al.…”

“…h) are described for Hemerobius and Dichochrysa (Neuroptera) (Zizzari et al. ). *Large space between the sperm plasma membrane and the acrosome + nucleus complex: (0) absent; (1) present. A large space occurs in Galloisiana (Grylloblattodea) (Dallai et al.…”

“…Wing-like lateral expansions ( Fig. 1h) are described for Hemerobius and Dichochrysa (Neuroptera) (Zizzari et al 2011). 17 *Large space between the sperm plasma membrane and the acrosome + nucleus complex: (0) absent; (1) present.…”

“…(1) absent. The acrosome vesicle is missing in Acerentomon (Protura) (Dallai et al 2010a), Mastotermes, Peruphasma (Euphasmatodea), Hydropsyche (Trichoptera), Micropterix (Lepidoptera) and Dichochrysa (Neuroptera, present in Hemerobius) (Zizzari et al 2011). 4 Placement of the acrosome vesicle: (0) surrounding the tip of the sperm anterior pole; (1) adapted to a cavity of the nucleus; (2) extending alongside the length of the nucleus;…”