Cytogenetic studies following high dosage paternal irradiation in the mealy bug, Planococcus citri: I. Cytology of X1 embryos
In the mealy bug, Planococcus citri, following high dosage paternal irradiation (60,000 to 120,000 rep), the survivors are mostly female (about 30 to 40% of the unirradiated control value) whereas very few males survive (about 5% of control value). After lower doses of paternal irradiation (P.I.), however, few or no females survive while the normal number of males (never less than the control value) survive. The females developing after high dosage P.I. are gynogenetic and are triploid or diploid or 3N/2N or 2N/N mosaics. The cytology of X1 embryos following 90,000 rep is described in comparison with data from embryos following lower doses (8,000 r) of P.I. and unirradiated controls, to illustrate the chromosomal mechanisms leading to the production of gynogenetic females and the probable reasons for lethality of X1 males after heavy P.I. It has been shown that triploid females stem from a fusion nucleus of the first and second polar bodies. This triploid polar nucleus, which normally participates in the formation of a polyploid sector in the young embryo, undertakes a successful embryogeny in many embryos when the zygote nucleus is unable to do so because of the heavily damaged paternal complement of chromosomes. Since the chromosomes are characterized by holokinetic activity, the irradiated paternal set manages to divide with the maternal complement but did not always segregate as successfully. Restitution divisions of the zygotic nuclei result in haploid, hyperhaploid, diploid and polyploid nuclei. Most of the diploid gynogenetic females probably originate from diploid nuclei of zygotic origin although it is possible that a few diploid females and the 2N/N mosaic females develop from polar bodies.
- Research Organization:
- Univ. of California, Berkeley
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-000067
- OSTI ID:
- 4163877
- Journal Information:
- Chromosoma, Vol. 14, Issue 3; Other Information: Orig. Receipt Date: 31-DEC-64; ISSN 0009-5915
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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