On the chromosomes of some species of the zygopterous dragonflies (Odonata, Zygoptera)

Abstract

(1) The numerical relations of the chromosomes studied in the male germ cells of seven species belonging to Lestidae and Coenagriidae (Zygoptera-Odonata) obtained from several localities of Japan are given in Table 1.(2) Without exception, there is present an unpaired X-chromosome in all species investigated. It is always divided into equal halves in the first division, while in the second division it migrates to one pole without separation. The size of the X is rather variable among the species. In Agriocnemis selenion, the X is represented by the largest element in the complex, while in the other species it is the smallest chromosome in the garniture except the m-chromosome.(3) The seven species herein studied always contain the so-called m-chromosome of minute size, which shows a considerable variation in size from species to species. It is interesting to find that the m-chromosome of Lestes sponsa shows individual variation in size (see Figs. 4-5).(4) The following four species belonging to the Coenagriidae, viz., Agrion (Coenagrion) hieroglyphicum, Ischnura senegalensis, Agriocnemis selenion and Copera annulata, possess spermatocyte chromosomes of a huge size, while in the members of the Lestidae the chromosomes are not so great in magnitude.