Effects of b chromosomes on development in grasshopper embryos

Abstract

Pre- and post-diapause embryonic development was described in Myrmeleotettix maculatus in 24 stages up to hatching. The rate of development and mitotic index of 0B, 1B and 2B karyotypes in males and females were compared in the laboratory in material from two disjunct locations. The overall influence of one B chromosome on development does not appear to be major; however, higher numbers of Bs have a more noticeable effect. The B chromosome quite clearly slows down the early prediapause development of male embryos, and individuals with 2B or 3B chromosomes are on average retarded in the later stages of the post-diapause period prior to hatching. The presence of B chromosomes produces a variety of chromosomally mutant embryos, many of which are arrested prior to diapause and few develop to hatching. The results are discussed in relation to the maintenance of the B chromosome polymorphism in this insect. © 1978 The Genetical Society of Great Britain.