Abstract
The chromosomes were investigated in male germ cells of Luperodes praeustus Mo tsch. (Chrysomelidae; Coleoptera) with special regards to the structure of the sex chromosomes. The number of chromosomes was determined as 32 in diploid and 16 in haploid (Figs. 1, 2, 8, 10, 11). The male of the present species was found to possess the sex chromosomes of an unequal X-Y pair, a large V-shaped element representing the X and a little smaller J-shaped one the Y. The female was ascertained to be homogametic for the X, since the large V-shaped element is present in a paired condition (Fig. 3). The autosomes are relatively small in size as compared with the X and Y; they appear in the form of curved rod and obscure V, on account of the presence of a remarkable constriction in each.
From the observations through the meiotic prophase, it was pointed out that the sex chromosomes are multiple in structure. The X consists of three components, resulted in the fus on of the original X-element with two autosomes (A and B). The Y chromosome is also of multiple nature, being composed of the a and b elements which are homologous for A and B respectively (Figs. 18-20). It is noticeable that in early prophasic nuclei of meiosis, the autosomal parts of both X and Y take the form of the chromonema thread, while the original X-part remains as the heteropycnotic condensed body (Figs. 4, 5).
In conjugation the Y associates with the autosomal arm of the X. At the first metaphase, the XY complex stands vertical on the equatorial plate, with the autosomal arm of the X parallel to the axis of the spindle (Figs. 9, 12, 13, 14, 15). In the first division, the X and Y separate, and migrate to opposite poles, resulting two sorts of secondary spermatocytes, the X-class and the Y-class (Figs. 10, 11).
