Distribution of intramembranous particles and filipin‐sterol complexes in the spermatid and spermatozoon of Culex quinquefasciatus (Culicidae)

Abstract

Distribution of intramembranous particles and filipin-sterol complexes in the spermatid and spermatozoon ofCulex quinquefasciatus (Culicidae)Sônia N Báo Wanderley de Souza Abstract A freeze-fracture study was carried out on spermatid and spermatozoon of the mosquitoCulex quinquefasciatus. In the spermatid plasma membrane few and randomly distributed intramembranous particles were observed. In the spermatozoon the density of intramembranous particles was higher on the P-than on the E-fracture face of the plasma membrane. Two populations of particles were observed. Large particles (about 15 nm in diameter) are regularly arranged in double rows as a zipper-line, longitudinally oriented in relation to the main cell axis. These strands of particles were observed in the posterior head region, mainly associated with the E-fracture face. Filipin was used to analyse the presence and distribution of cholesterol in thin sections and freeze-fracture replicas. Filipin-sterol complexes were not homogeneously distributed throughout the spermatozoon plasma membrane. They were more abundant on the P-fracture face of the membrane lining the nuclear region. The results obtained show thatCulex spermatozoon differs from those of other species in that its plasma membrane exhibits only a membrane domain, the zipper-line, localized in the postacrosomal region.

A novel membrane specialization in the sperm tail of bug insects (heteroptera)

“…This insect specialization was formerly seen in freeze-fracture replicas by Baccetti et al (1971) and further by Dallai and Afzelius (1982) and identified in cross sections as short filaments between the plasma membrane and the thinner part of the right mitochondrial derivative. In Culex quinquefasciatus, such specialization was hypothesized to be located at the postacrosomal region (Bá o and de Souza, 1992). Another structure, also similar to the ''zipper line,'' was recently described in Drosophila species provided with different sperm lengths.…”

Structural organization of the “zipper line” in Drosophila species with giant spermatozoa

“…The particles were seen mainly associated with the P-face of the plasma membrane. Báo and de Souza (1992) observed a similar structure in freeze-fracture replicas of the mosquito sperm plasma membrane.…”