Morphogenesis of the giant sperm axoneme in Asphondylia ruebsaameni Kertesz (Diptera, Cecidomyiidae).
The formation of the sperm giant axoneme of the gall-midge fly Asphondylia ruebsaameni is described here. The axoneme consists of a great number of microtubular doublets (up to 2,500) arranged in a double spiral wrapping around an axial cluster of mitochondria. Each microtubular doublet is provided with an outer arm only. In the early spermatid the occurrence of a large system of curved multi-layered filamentous material associated with membranous cisternae has been observed in the perinuclear region. Such a system extends throughout the cytoplasm to contact the plasma membrane. The filamentous material appears to act as a nucleating centre for the assembly of the microtubular doublets, which initially have a submembranous location and later are distributed in the interior of the cell. After their assembly, microtubular doublets are associated pairwise and are arranged in a single microtubular row with a zig-zag configuration. This configuration changes during spermiogenesis as a consequence both of a rotation of the microtubular doublet pairs and a compaction of the axonemal complex due to the elimination of the excess cytoplasm. As a result of this process, a double parallel spiral of microtubular doublets is formed.
Mencarelli
C
C
Department of Evolutionary Biology, University of Siena, Italy.
Lupetti
P
P
Rosetto
M
M
Dallai
R
R
D000818:Animals; D004175:Diptera / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D008854:Microscopy, Electron; D009942:Organometallic Compounds; D013082:Sperm Tail / Q000648:ultrastructure; D013091:Spermatogenesis; D013194:Staining and Labeling
D009942:Organometallic Compounds; C005460:uranyl acetate