Serial sectioning study of some meiotic stages in Scaptericus borrelli (Grylloidea)

An electron microscope study of the spermatocytes I of Scaptericus borrelli was performed using serial sections and tridimensional reconstruction. The stages examined were: mid-pachytene, early diplotene and the so-called diffuse stage. At mid-pachytene the nucleolus (associated to an autosome) shows a glomerular array formed of supernumerary synaptonemal complexes (extra-complexes, ECs). At early diplotene the autosomes still show remnants of synaptonemal complexes (SC) and the sex chromosome is formed by two substances: one is homogeneous (chromatin-like) the other is granular and dense. A short number of ECs occur in the latter. — At the diffuse stage (lobulated in this paper) the SCs remnants and the ECs have disappeared and the granular material is assembled in a nuclear lobule. This lobule was found associated with one centriole. — A tridimensional model of a diplotene nucleus and models of diplotene bivalents are shown. — The capacity to form repetitive components of the synaptonemal complex type by spermatocytes of the super-Family Grylloidea is discussed.