Cytogenetics of Oryctes nasicornis L. (Coleoptera: Scarabaeidae: Dynastinae) with Emphasis on Its Neochromosomes and Asynapsis Inducing Premature Bivalent and Chromosome Splits at Meiosis

The chromosomes of specimens of Oryctes nasicornis from three locations in France and two locations in Greece were studied. All karyotypes have an X-Y-autosome translocation: 18, neoXY. Two male specimens from France (subspecies nasicornis) displayed an unusual behaviour of their meiotic chromosomes in 30–50% of spermatocytes, with asynapsis at pachynema, premature bivalent and chromosome split at metaphases I and II. The karyotypes remained balanced at metaphase I, but not at metaphase II. These particularities mimic the meiotic behaviour of B chromosomes and question about their existence, reported earlier in Spanish specimens. Due to the variable character of B chromosomes, complementary analyses are needed. To our knowledge, such meiotic particularities have not been described, beside cases of infertility. In specimens from Corsica (subspecies laevigatus) and Greece (subspecies kuntzeni), all spermatocytes I and II had a normal appearance. The meiotic particularity may thus be limited to male specimens from subspecies nasicornis.