The sperm structure of the gall-midges Anaretella and Lestremia (Insecta, Diptera, Cecidomyiidae)

The evolution of sperm axoneme structure and the dynein heavy chain complement in cecidomid insects

“…Two distinct evolutionary trends have occurred within this group, one comprising the subfamilies Lestremiinae and Cecidomyiinae, and the other leading to Lasiopteridae [Dallai and Mazzini, ; Dallai et al, ]. The first trend still retains a geometric—though deeply altered—organization of the axoneme, which is characterized by the absence of the central complex (substituted for by elongated, axial mitochondria), by a progressively increasing number of doublets (up to 2500 in Asphondylia) , and by the loss of the inner dynein arms, which are only present in the less evolved Lestremiinae [Dallai and Mazzini, ; Dallai et al, ]. However, and albeit only under particular conditions, these sperm cells are motile [Lupetti et al, ; Mencarelli et al, ].…”

“…In fact, we have reported that the loss of the central pair/radial spoke complex is not only followed by the loss of the inner dynein arms, but also results in a reduced complement of heavy chains in the outer dynein arms [Lupetti et al, ; Mencarelli et al, ]. The sperm cells of the species belonging to the other trend, on the contrary, assemble 9 + 0 axonemes that are able to maintain their ultrastructural integrity only in their very proximal part, after which doublets appear scattered in the cytoplasm [this article; Dallai and Mazzini, ; Dallai et al, ]. Both dynein arms are lost in this evolutionary lineage, and sperm cells are immotile.…”