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

Abstract

The sperm ultrastructure of the Grylloblattodea Galloisiana yuasai was described and the sperm characters were comparatively examined in several orthopteroid insect orders for inferring the phylogenetic placement of the Grylloblattodea. The spermatozoa of G. yuasai are joined in bundles (spermatodesms) containing 200 units. Major features of these spermatozoa include a monolayered acrosome, a 9+9+2 axoneme with 16-pfs accessory microtubules and expanded intertubular material, and an evident ''centriole adjunct''. The diffused material observed between the axoneme and the mitochondrial derivatives is considered to be an extension of the three connecting bands observed in other orthopteroid taxa, similar to what happens in some orthopteran lineages. The presence of the connecting bands, even though modified in G. yuasai, suggests that the Grylloblattodea are to be placed in a clade with Mantophasmatodea, Mantodea and Orthoptera.

The sperm structure of Embioptera (Insecta) and phylogenetic considerations

“…These characteristics were also found in the previously studied species Haploembia solierii (Baccetti et al 1974) and can be found in all diVerent polyneopteran species studied so far (Dallai et al 2003(Dallai et al , 2005.…”

“…A trilayered acrosome is, for instance, the typical pattern of Blattodea, Dermaptera, Orthoptera and Plecoptera. The only taxon so far examined showing a spermatozoon provided with a monolayered acrosome is the Grylloblattodea (Baccetti 1982;Dallai et al 2005), which would suggest their aYnity with Embioptera. Nevertheless, Grylloblattodea have other sperm features in common with other orthopteroid insects, such as Mantodea, Orthoptera and the recently described taxon Mantophasmatodea (Dallai et al 2005), but not shared with Embioptera.…”

“…Among them, the presence of a monolayered acrosome is a sign of derived specialization, because basal insects have a tri-or bilayered acrosome provided with a perforatorium (Dallai et al 2003(Dallai et al , 2005. A trilayered acrosome is, for instance, the typical pattern of Blattodea, Dermaptera, Orthoptera and Plecoptera.…”

Cryo-electron tomography reveals conserved features of doublet microtubules in flagella

“…Classic EM studies of chemically fixed flagella have occasionally observed electron-dense material in the lumens of axonemal MTs, especially in insect sperm tails (20,21). Two recent reports have described MIPs that bind periodically to the luminal side of the DMT walls (8, 10) ( Fig.…”

Postembryonic development of the unique antenna of Mantophasmatodea (Insecta)

“…On the morphological side, the presence of ''connecting bands'' in the flagellum of the spermatozoa supports a clade comprising Mantophasmatodea, Grylloblattodea, Dictyoptera and Orthoptera (Dallai et al, 2003(Dallai et al, , 2005. A sister group relationship between Mantophasmatodea and Grylloblattodea is vaguely indicated by a few characters most of which, however, show a high degree of homoplasy across the Insecta: various embryonic features , ovariole morphology and ultrastructure (Tsutsumi et al, 2005), similarities in the mandibles (Baum et al, 2007) and proventricle (Klass et al, 2002), and absence of wings and ocelli (Beutel and Gorb, 2006).…”