Chromosomes of the primary spermatocytes of Nephotettix nigropictus (Stal) [Philippines]
1986
Saxena, R.C. | Barrion, A.A. (International Centre of Insect Physiology and Ecology (Kenya))
The testicular primary spermatocytes of newly emerged green leafhopper N. nigropictus contained first meiotic holocentric chromosomes. At diakinesis the genomic complement consisted of 7 bivalent autosomes plus a univalent X-chromosome. Therefore the diploid chromosome number of male N. nigropictus is 2n = 5 (7IIA + XO). The prospective spermatozoa are of 2 types: n = 8(7IA + X) and n = 7(7IA + O). During metaphse I, the heterochromatic X-body can be seen isolated from autosomes at the equatorial plate. Pachytene analysis showed that the whole genome of males consisted of eight linkage groups. The longest autosome was almost double the shortest. The relative mean lengths of chromosomes ranged from 0.062 to 0.165. The six chromosome measured 0.062 and the autosome with the nucleolar organizing region (NOR) 0.155. The chromosomes condensed maximally during premetaphase into dumbbells of bivalent measuring 3.9 micron, 3.3 micron (NOR), 2.7 micron, 2.5 micron, 2.4 micron, 2.1 micron, 2.0 micron, and 1.6 micron (X). Their corresponding chromosome volumes were 0.025 micron to0807the third power, 0.015 micron to the third power, 0.009 micron to the third power, 0.007 micron to the third power, 0.007 micron to the third power, 0.004 micron to the third power, 0.003 micron to the third power, and 0.001 micron to the third power. The mean meiotic index approximated 0.61, the mean number of dividing spermatocytes was 227, the number of nondividing cells was 147. Of 100 cells at diakinesis, 24% contain a reduced number of bivalents and 5% possessed an increased number of chromosom
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