CYTOGENETICS OF 2 NORTH-GERMAN POPULATIONS OF NOSOPSYLLUS FASCIATUS BOSC (APHANIPTERA)

Specimens of the populations Hamburg and Wilhelmshaven of the ratflea N. fasciatus exhibit variation of the chromosome number in the range of 2n=20-23 and 2n=20-27 respectively, resulting from individual differences in the number of supernumerary chromosomes beyond the basic chromosome complement of 2n=20. The supernumerary chromosomes are mostly euchromatic and partly or completely homologous to each other and to the 10. pair of the basic complement. The numerical variation in the population Wilhelmshaven is produced by recurrent mitotic non-disjunction of the supernumerary chromosomes in anaphase II of spermatogenesis. Constant mitotic non-disjunction and preferential segregation of the supernumerary chromosomes towards the pronucleus leads to their accumulation in the population.-A multiple sex-chromosome mechanism of the type X1 X2 Y1 Y2 (male): X1 X1 X2 X2 (female) has been demonstrated for the population Wilhelmshaven of N. fasciatus. The X1 X2 Y1 Y2-chain of four is restricted to the male meiosis, in oogenesis two sex bivalents (X1 X1 and X2 X2) are formed. - The cytogenetic data presented do not support the concept of a closer phylogenetic relationship between the Aphaniptera and Nematocera, but do not preclude the possibility of a kinship of Aphaniptera and Neomecoptera. © 1969 Springer-Verlag.