Summary
A modified Comstockiella chromosome system is described in the olive scale insect, Parlatoria oleae (Colvée), in which one, two, or three pairs of chromosomes may play the D role during spermatogenesis.
In the male, one set of chromosomes became heteropycnotic in the embryo and remained so until spermatogenesis. Prior to the meiotic prophase, some of the heteropycnotic (H) chromosomes became euchromatic and the number of these chromosomes was cyst-specific. Those chromosomes of the H set which remained heteropycnotic are referred to as DH elements and these chromosomes together with their euchromatic (E) homologues are called the D pairs.
During prophase and metaphase, 4 E and from one to three H elements were present. The number of H elements was considered to be an indication of the number of pairs which did not undergo pairing (D pairs). Thus in cysts with 1H and 4 E elements, 3 of the E elements were considered to be bivalents while 1 E and 1H elements were considered to be univalents.
All the chromosomes at metaphase were of about the same size. This was taken to mean that the univalents replicated prior to meiosis while the bivalents did not.
During anaphase, all the elements divided, with 4 E and from one to three DH derivatives going to each pole. In the stages which followed telophase, the DH derivatives segregated from the 4 E chromosomes. During spermiogenesis, only the nuclei with the E chromosomes formed functional sperm.
On the basis of the analysis of pairing in the Comstockiella system and in other coccids, it is suggested that in the Comstockiella system, and probably also in other coccids, when pairing is not associated with chiasma formation, the homologues entering pairing are unreplicated chromosomes.
The modified Comstockiella system found in P. oleae is called the multiple-D variant and is considered to be an intermediate between the lecanoid and the simple Comstockiella systems. The presence of such intermediates was predicted by Brown (1963 and 1964) who considered the evolution of the Comstockiella system to be the product of automatic frequency response.
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Postdoctoral Trainee in Biology, U.S. Public Health Service 1962–1963.
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Nur, U. A modified Comstockiella chromosome system in the olive scale insect, parlatoria oleae (Coccoidea: Diaspididae). Chromosoma 17, 104–120 (1965). https://doi.org/10.1007/BF00330077
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DOI: https://doi.org/10.1007/BF00330077