X-ray induced rearrangements between germ-line limited and soma chromosomes of Acricotopus lucidus (Diptera,Chironomidae)

The germ-line limited chromosomes (Ks) [K being derived from Keimbahn (Bauer, 1970)] of Acricotopus lucidus were studied in gonial and differential mitosis. After C-banding the soma chromosomes (Ss) are stained only at their centromeric regions whereas the Ks exhibit centromeric, intercalary and terminal heterochromatin. By X-raying sperms it was attempted to transfer K sections on or into Ss in order to bring finally S-linked K sections to polytenization in the salivary glands, and to obtain more knowledge about the structure of Ks. Seven F₁-larvae were detected with K-S-rearrangements: four with insertions of heterochromatic segments, two with insertions of sections with S-homologous banding pattern and one with a translocated K chromosome part, which consists of S-homologous euchromatic sections as well as of an intercalary and a terminal heterochromatic segment. The present results strongly suggest that the Ks of A. lucidus are derived from the Ss by rearrangements and by formation and accumulation of repetitive sequences.