Synaptonemal complexes in the mosquito Culex quinquefasciatus
The presence of synaptonemal complexes between the paired homologous chromosomes at meiotic prophase is a prerequisite for meiotic crossing over, and it may be important for the regular disjunctions of the chromosomes at meiosis I (Moses, 1968; Westergaard and von Wettstein, 1972; Gillies, 1975). Reconstructions of nuclei during zygotene and pachytene have shown that the ends of the synaptonemal complexes in many organisms are attached to the nuclear membrane, often in a polarized fashion (Moens, 1969; Rasmussen, 1976); such a bouquet arrangement of the chromosomes is found in Culex.Materials and MethodsOvaries from Culex quinquefasciatus were fixed in glutaraldehyde, followed by 0s04, and embedded in Epon. The synaptonemal complexes were reconstructed from serial sections.Results and DiscussionCulex has 3 pairs of very long metacentric or slightly submetacentric chromosomes which during pachytene loop around the nucleus several times (Fig. 1). The centromeric regions are fused, and the synaptonemal complexes do not continue through the structure.