The genetic diversity of the parthenogenetic gall wasp Diplolepis rosae is investigated by a survey of 26 enzyme loci. D. rosae, which is confined to roses (Rosa) and reproduces by obligate gamete duplication, was sampled from five host-plant species in southern Sweden. Additional galls were obtained from Germany and Greece. Eight genotypes were determined on the basis of nine variable loci. The genotypes are not correlated to host-plant species, and in some cases differ in geographical distribution, indicating adaptation to climatic factors. The consequences of gamete duplication for the genetic diversity and ecology of D. rosae are discussed.

First meiotic division in females and males of Yponomeuta evonyrnellus (L.), Y. cagnagellus (Hiibner). Y. rnalinellus Zeller, Y. padellus (L), Y. rorellus (Hiibner) and Y. gigas Rebel was studied in the light microscope. In the heterogametic females the sex chromosomes were found to be associated in a sex chromosome trivalent. The sex chromosome trivalent, written AAWZ, consisted of a W‐chromosome translocated to an autosome to form an Aw‐chromosome, which was paired with the homologous auto‐some and the 2‐chromosome. In the homogametic males the two Z‐chromosomes were paired in a usual bivalent. The sex chromosome inheritance can be balanced in this way. The haploid chromosome number was n = 29 A + AAWZ in females and n = 30 A + ZZ in males, for all species examined. It is of interest to notice that the chromosome number of Y. rorellus earlier has been differently determined to be n = 29 for males. Especially in females the bivalents were observed to be nonhomologously associated at the telomeres during meiotic prophase.

An attempt was made to illustrate by light-microscope photomicrographs and drawings the females meiosis and fertilization of Drosophila melanogaster. The centromeric regions of the meiotic prophase chromosomes form a chromocenter whereas the telomeric parts adhere to the nuclear membrane. The meiotic process is correlated with the successive stages in the development of the egg follicle.

No abstract

No abstract