A Further Study on the Chromosomes of the Parthenogenetic Weevil, Listroderes costirostris Schönherr, from Japan

The chromosomes of Listroderes costirostris Schönherr obtained from Kurashiki City, Okayama Prefecture, Japan, were studied in both oogonial and oocyte-maturation divisions in squash and sectioned slides, respectively. Oogonial chromosome-numbers varied between 28 and 41+ in 1967, and between 27 and 30, and 28 and 31 in 1968. The commonest number encountered was 30. Three metaphase plates of the single equational maturation division showed 28, 29, and 30 unpaired chromosomes. One oocyte metaphase plate was tripartite and “a rudimentary reduction division” was often observed. It is, therefore, concluded that L. costirostris is a parthenogenetic polyploid in Kurashiki City. A karyotype analysis revealed a probable base number of ten, and hence strongly suggests triploidy.