Post-meiotic Splitting of Spermatid Nucleus and Beaded Tail Formation During Spermiogenesis to Eliminate DNA in Two Grasshoppers With B Chromosomes

Abstract

: The end product of meiosis in male grasshoppers is round spermatids and these will not undergo post meiotic division, under normal conditions. In two species of grasshoppers carrying B chromosomes, the postmeiotic division of the nucleus of spermatids was observed. The number of nuclear bits formed ranged between 1-4 in the elongating head region of developing spermatids during spermiogenesis. The nuclear bits were also pushed in to the tail region resulted in a beaded appearance to the tail of sperm, with five to ten number of nuclear bits in the tail region. Addition to this small, round micro-spermatids formed from the eliminated nuclear bits, remained the same without showing further development. The range of nuclear bits generated outnumbered the B chromosomes encountered in the two species of grasshoppers. The grasshopper Neorthocris acuticeps acuticeps had one small B and the other Chrotogonus trachypterus had two kinds of Bs- large and small. This unusual process of post-meiotic division of the spermatid nucleus and beaded tail formation in sperms is discussed in the light of DNA elimination during gametogenesis in males of grasshoppers.