Sperm structure of Mecoptera and Siphonaptera (Insecta) and the phylogenetic position of Boreus hyemalis

Abstract

Sperm ultrastructure has been studied in three species of the taxa Mecoptera and Siphonaptera. The spermatozoon of the scorpion fly Panorpa germanica shows an apical bilayered acrosome, a helicoidal nucleus, a centriolar region and a 9+2 flagellar axoneme helicoidally arranged around a long mitochondrial derivative. A second mitochondrial derivative is very short and present only in the centriolar region. A single accessory body is present and it is clearly formed as a prolongation of the centriole adjunct material. Two lateral lamellae run parallel to the nucleus. The snow fly Boreus hyemalis has a conventional sperm structure and shows a bilayered acrosome, a long nucleus, a centriolar region, two mitochondrial derivatives and two accessory bodies. The axoneme is of the 9+2 type and is flattened at the tail tip. Both P. germanica and B. hyemalis have two longitudinal extra-axonemal rods and have a glycocalyx consisting of longitudinal parallel ridges or filaments. The spermatozoon of the flea Ctenocephalides canis has a long apical bilayered acrosome, a nucleus, a centriolar region, a 9+2 axoneme wound around two unequally sized mitochondrial derivatives, and two triangular accessory bodies. In the posterior tail end the flagellar axoneme disorganises and a few microtubular doublets run helicoidally around the remnant mitochondrial derivative. The glycocalyx consists of fine transverse striations. In all three species, the posterior tail tip is characterised by a dense matrix embedding the disorganised axoneme. From this comparative analysis of the sperm structure it is concluded that Mecoptera, as traditionally defined, is monophyletic and that B. hyemalis is a member of Mecoptera rather than of Siphonaptera.

The sperm structure of Galloisiana yuasai (Insecta, Grylloblattodea) and implications for the phylogenetic position of Grylloblattodea

“…Sperm cells have a variety of different ultrastructural characters which can provide useful information for reconstructing phylogenetic relationships at different taxonomic levels (Dallai et al 1996a(Dallai et al , 1996b(Dallai et al , 2003b(Dallai et al , 2004. This is particularly true in insects where the presence of accessory tubules and several other specializations sometimes offer a vast number of different characters that can be used in cladistic analyses.…”

Spermatozoon Ultrastructure of Hangingflies,Bittacus strigosusandBittacus stigmaterus

“…This extension is known as an accessory body (AB) (Dallai et al 2003). In Mecoptera, there have been consistent reports of the presence of CAM and ABs in spermatozoa, but there is variation in its description among the species (Baccetti et al 1969;Gassner et al 1972;Dallai et al 2003;Xie and Hua 2010).…”

“…Several previous studies have included ABs and EARs in their descriptions of spermatozoon ultrastructure (Breland et al 1966;Gassner et al 1972;Dallai et al 2003;Xie and Hua 2010), but identification of these structures has been inconsistent and confusing among the publications. Clarification of the differences between ABs and EARs was included in this study due to the importance of these structures in terms of phylogenetic considerations.…”

“…Comparisons of spermatozoon ultrastructure are often used to help establish phylogenetic relationships among insects (Baccetti et al 1969;Gassner et al 1972;Jamieson et al 1999;Dallai et al 2003;Xie and Hua 2010). Documentation of the spermatozoon ultrastructure from additional members of the genus Bittacus has particular merit, since phylogenetic evaluation carries more validity with a greater number of described species.…”

“…The spermatozoon ultrastructural components of these species were also compared to Bittacus planus Cheng (Xie and Hua 2010) to discover if the structures considered important for phylogenetic placement were present in all three species. These structures were a short bilayered acrosome, tube-like glycocalyx, extra axonemal rods (EARs), elongated nucleus, centriole adjunct material (CAM), two mitochondrial derivatives (MDs), accessory bodies (AB), 9+2 arrangement of axoneme microtubules, and globular units (Dallai et al 2003;Xie and Hua 2010).…”