Cytogenetic Analysis of Partial Elimination of Germ Line Limited Chromosomes from Primary Germ Cells in Acricotopus lucidus (Diptera, Chironomidae)

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Unusual mitotic behavior of additional chromosomes present only in the germ line was reported for the dipteran families Cecidomyiidae, Chironomidae and Sciaridae, which are known to have complex chromosome cycles. In the chironomid Acricotopus lucidus all germ line limited chromosomes (=Ks) are eliminated from the future somatic nuclei during germ line-soma differentiation in early, still syncytial, embryonic divisions by remaining in the equatorial plane. But also in the germ line about half of the Ks are eliminated in the first mitotic division of the primary germ cells in the young gonads of first instar larvae. Until now not much is known about the cytogenetic processes in the course of germ line elimination of the Ks. In this study, the cytogenetic changes in the primary germ cells before, during and after the elimination mitosis were analysed in detail with DAPI stained gonad preparations.