Interessante comportamento dos cromossômios na espermatogênese dp escorpião Isometrus maculatus De Geer

Resumo

Having had the opportunity of studying a male of the species Isometrus maculatus De Qeer (Scorplones, Buthidae) the author was able to observe one of the most interesting anomalies hitherto met with in his investigations on Scorpions. This anomaly consisted in the formation by the primary spermatocyte metaphase chromosomes of a complex group of eight elements, and two independent pairs. As it is clear, the octovalent group resulted from tranlocations involving the members of four chromosome pairs. Since aside the compound group two independent bivalents were always present, 12 was estabilished as representing the diploid chromosome number of the individual, what was soon confirmed by the counts in the spermatogonia. This peculiar behavior of the chromosomes of the primary spermatocytes represents the habitual condition in the studied individual, since it was found everywhere in the whole testis. Better than any description, the figures in this, paper show what was observed. Notwithstanding the complications which may occur at anaphase, separation of the chromosomes goes normally, each pole receiving four chromosomes from the group and two from the free bivalents. Secondary spermatocytes are thus provided with six monovalents. Though not found, we may believe in the existence of secondary spermatocytes with more or lesse than six chromosomes, because it seems highly probable that lhe chromosomes of the complex may now and then passe to the wrong pole 'n consequence of an incorrect orientation. Bridge vestiges suggest that chromosomes may sometimes break. The spermatogonia have 12 short chromosomes, which bend to the poles at anaphase. The chromosomes of the present species approach, in shape and behavior, those of Tityus mattogrossensis.