SPERMATID NUCLEUS OF MEGASELIA-SCALARIS LOEW (INSECTA, DIPTERA, PHORIDAE) - A STUDY USING ANTIHISTONE ANTIBODIES, SCANNING ELECTRON-MICROSCOPY, AND A CENTROMERE-SPECIFIC OLIGONUCLEOTIDE

The structure of elongated spermatid nuclei was examined in the fly Me gaselia scalaris using indirect immunofluorescence with anti-histone a ntibodies, scanning electron microscopy, and in situ hybridization wit h a centromere-specific oligonucleotide. The immunofluorescence experi ments showed that, in keeping with the situation in most animals, hist ones are hyperacetylated prior to their displacement from the nucleus in the course of spermiogenesis. Scanning electron microscopy revealed that grooves run parallel to the long axis of the spermatid nuclei. T he chromatin is segmented into blocks lateral to the grooves. This fin ding most probably indicates that the chromatin is not yet maximally c ondensed at this stage. The retarded chromatin condensation may be cor related with the export of somatic histones from the nucleus. The loca tion of the centromeres could not be identified using scanning electro n microscopy, but in situ hybridization showed that a centromere-speci fic oligonucleotide mapped to the central or close to the central area s within the spermatid nucleus. Possibly, the chromosomes are extended and arranged parallel to the long axis of the spermatid nucleus. (C) 1993 Wiley-Liss, Inc.