, Volume 20, Issue 2, pp 234–250 | Cite as

Fine structure of meiotic chromosomes comparative study of nine species of insects

  • J. Roberto Sotelo
  • Rodolfo Wettstein


A comparative electron microscope study at magnifications ranging from about 80,000 up to 800,000 x was carried out in nine species of insects (Gryllus argentinus, Myogryllus verticalis, undetermined species of Gryllus; Blaptica dubia, Periplaneta americana, Blattella germanica; Laplatacris dispar, Aleua lineata and Omexechae servillei). Particular attention was paid: a) to the elementary components of the s. complexes and b) to the structure of their medial ribbon. - a) In all the species examined the basic element found is a curled filament some 15–20 Å thick. Filaments of this kind integrate: the 100 Å fibrils of the chromosome body, the compacts layers of the s. complexes (lateral arms) and the slender planes of the pairing space. The filaments are similar to those described in metaphase chromosomes and their kinetochores (Wettstein and Sotelo, 1965). A difference in density between the filaments of the lateral arms and those of the medial planes is sometimes noticed. - b) Three structural patterns were found in the pairing space. In crickets, the medial ribbon is composed of three parallel, longitudinal planes of filaments, interconnected and connected with the lateral arms by means of bridges. The latter are constituted by fibrils or by single filaments. In cockroaches only two longitudinal planes were found. The distribution of components in these planes follows a plan similar to the one found in crickets. In the electron-micrographs the medial component of both groups of Insecta appears as composed of three (crickets) or two (cockroaches) lines in the longitudinal frontal views, and ladder-like striated in lateral views. The latter striae correspond to filaments or groups of filaments running in antero-posterior direction. - The pattern of structure of grasshoppers differs completely from those mentioned above. Bridging between the homologues is made of regularly spaced transversal planes of filaments. No longitudinal array was observed.


Fibril Medial Component Frontal View Metaphase Chromosome Medial Plane 
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Copyright information

© Springer-Verlag 1966

Authors and Affiliations

  • J. Roberto Sotelo
    • 1
  • Rodolfo Wettstein
    • 1
  1. 1.Departamento de Ultraestructuar Celular MontevideoInstituto de Investigación de Ciencias BiológioasUruguay

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