THE CHROMOSOME CYCLE OF PHENACOCCUS (COCCIDÆ)

¹ From the Department of Zoölogy, Columbia University

1. The diploid chromosome number of Phenacoccus acericola is twelve in both sexes.

2. The female is normal in all respects. All eggs undergo two maturation divisions with typical synapsis and reduction of the choromosomes to the haploid condition.

3. In the male, from the blastula stage of development on, one haploid set of chromosomes maintains a permanently condensed condition, forming a pycnotic knot in resting phases and separating into its component chromosomes at division.

4. Meiosis in the male is effected without synapsis. The first division is equational and diploid. Without interphase the telophase chromosomes separate into two groups of six, one condensed and closely aggregated, and one loosely arranged and more diffuse. A single half spindle forms in connection with the condensed group and reduction is effected by the consequent passage of the condensed group to the single pole of the spindle.

5. No cytoplasmic division accompanies the second division; the binucleate spermatids thus formed fuse in pairs.

6. That half of the spermatid nuclei originating from the condensed chromosome set disintegrates without trace of sperm development; the other half of the spermatid nuclei, those originating from the nonpycnotic normal chromosomes, develops into typical coccid sperm.

This article has been cited by other articles:

				S. W. Brown and U. Nur Heterochromatic Chromosomes in the Coccids: The process of heterochromatization and the function of heterochromatin in coccid insects are reviewed Science, July 10, 1964; 145(3628): 130 - 136. [PDF]