Achiasmatic male meiosis in two species of Saldula (Saldidae, Hemiptera)

Abstract

Male meiosis in two species of Saldula, S. orthothila and S. saltatoria was studied. The diploid chromosome numbers were found to be 2n=32+m+XY and 2n=32+2m+XO respectively. The existence of a Y-chromosome was recorded for the first time in this primitive heteropteran genus. The meiotic behaviour of the sex chromosomes was found to be similar to that of sex chromosomes in more advanced Heteroptera. Autosomal bivalents during late meiotic prophase and metaphase I consisted of two parallelly aligned chromosomes. No traces of chiasmata could be found. The role of Y-chromosome in the evolution of sex chromosome systems in Heteroptera, the mechanisms behind the regular segregation of achiasmatic chromosomes, the adaptive significance of achiasmatic meiosis and the restriction of achiasmatic meiosis to the heterogametic sex are discussed.