Maintenance of B chromosomes in natural populations of Acrida lata MOTSCHULSKY in Kami-goto Ilands, Hirado-jima, and Tabira-chyo in Nagasaki Prefecture

Chromosomes of Acrida lata MOTSCHULSKY were studied using males collected in natural populations at four localities : Madara-jima and Uku-jima both of Kami-goto Ilands (upper part of Goto Ilands west to Kyushu), and Hirado-jima and Tabira-chyo in Nagasaki Prefecture (Fig. 1). Chromosome numbers of the males varied from 2n♂ =23 to 2n♂=25 due to B chromosomes, i. e., 2n♂ =22+X (consisting of A chromosomes only), 2n♂ =22+X+1B, and 2n♂=22+X+2B. The B chromosomes were the same as found in other populations in Kyushu (cf. Kayano, Sannomiya and Nakamura 1970). Mitotic chromosomes at metaphase of spermatogonia and meiotic chromosomes at metaphase of primary spermatocytes were shown in Figs. 2a-3b and Figs. 4-6. Frequencies (%) of males with B chromosomes in the four populations were 35.0 (Madara-jima), 24.4 (Uku-jima), 18.0 (Hirado-jima), and 17.0 (Tabira-chyo), 100 males being observed in each of the populations excepting the Uku-jima population in which 119 males were oberved (Table 1). The result was discussed bio-geographically taking the low mobility of A. lata into consideration