Abdel-Hameed, Fathi, 1938-||Bennett, Jack (Cecil Jackson)
M.S. (Master of Science)
Department of Biology
A cytological study was made of the chromosomes of several species of Orthopteran grasshoppers: Melanoplus femur-rubrum, M. differentialis differentialis, M. oregonsis, Asemoplus somesi, and Dissosteira carolina. Adult male grasshoppers were collected from natural populations and aceto-orcein squashes of testicular tissue were made. An electron microscopic study was also made of spermatogenesis in the grasshopper Chortophaga viridifasciata. The various populations were surveyed for the presence of B chromosomes (supernumerary chromosomes) and other numerical and structural anomalies. Determinations of chiasma frequencies were made from samples of all populations and all species studied. All populations of M. femur-rubrum and one of M. differentialis differentialis were found to be polymorphic for the presence of B chromosomes. The frequency of B carrying individuals varied between different populations of H. femur-rubrum, ranging between 3.75 and 17.77%. A majority of the B carriers had only one B chromosome, although individuals with as many as three B’s were observed. Two types of B chromosomes were observed in M. femur-rubrum. The most frequent type was a metacentric iso-chromosome, slightly smaller than the X chromosome. A smaller telocentric B chromosome was also observed fairly frequently. All B chromosomes were positively heteropycnotic at first meiotic prophase. They moved undivided to one of the poles at anaphase I. Segregation seemed to be random relative to the X chromosome, even though the B chromosomes frequently showed nonhomologous heterochromatic associations with the X chromosomes in earlier stages. Extensive work was done to correlate the presence of B chromosomes with a change in chiasma frequency, similar to that reported for other species. No correlation was found. Studies of variations in chiasma frequencies were made on several different levels: inter-specific, inter-populational, inter-seasonal, intra-seasonal, and intra-daily. No clear-cut relationships were found on any of these levels. In an inbred population of Asemoplus somesi, a series of translocations involving terminal segments of three chromosome pairs were observed. In the heterozygous state, the three chromosome pairs sometimes formed multiple associations which were seen in diplotene and sometimes persisted until metaphase I. On the ultrastructural level, observations were made of membraneous structures believed to be instrumental in the breakdown of the nuclear envelope during early meiosis. A cyclic "fragmentation" of the nucleolus was also observed in Chortophaga spermatocytes. Nebenkern formation and changes in the structure of the nucleus during spermatogenesis were also described.
Ball, David W., "A light and electron microscopic study of six species of Orthopteran grasshoppers with special emphasis on B chromosomes and chiasma frequencies" (1974). Graduate Research Theses & Dissertations. 383.
xii, 221 pages
Northern Illinois University
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