Meiosis inStethophyma(Mecostethus)Grossum(Orthoptera: Acrididae): An Exciting History

The present study is a sincere tribute from some of the cytogenetic laboratories of Madrid involved in the study of grasshopper meiosis, for the inestimable contribution of Professor Michael J.D. White to orthopteran cytogenetics, on the 100th anniversary of his birth. Here we review the knowledge accumulated over almost 90 y on the meiosis of the grasshopper Stethophyma grossum, especially on the male side, because of the very unusual meiotic characteristics shown by the spermatocytes, namely: whereas the three shortest bivalents achieve full synapsis and do not show chiasma localization and the single X chromosome remains asynapsed, the remaining eight bivalents show restricted synapsis and proximal chiasma localization. In addition, supernumerary segments and accessory chromosomes are present in some natural populations. Special attention is paid to the relationships among cohesin axis morphogenesis, initiation of recombination events and synapsis achievement.