Biomedical subjects
Publications and source records attributed to L Ehrman.
Six strains of the cosmopolitan species D. immigrans from the Australian life zone plus one from the USA, show weak sexual isolation and more rarely sexual selection. Levels of sexual isolation cannot be related to geographic distances. Assortative mating may have evolved as a byproduct of ecological divergence.
A successful attempt was made to culture the mycoplasmalike microorganism causing semispecific hybrid male sterility in Drosophila paulistorum utilizing Ephestia kühniella as the intermediate host. Data gleaned from this passage indicates that the induction of sterility depends upon the quality not the quantity of infectious intracellular symbionts.
Matings between Drosophila pseudoobscura strains differing at the amylase (Amy) locus were observed in Elens-Wattiaux chambers. Males homozygous for either Amy1.00 or Amy0.84 alleles in the CH gene arrangement enjoyed a mating advantage when moderately rare, but none when quite rare. The minority male advantage for strains differing at the Amy locus, and other loci linked to it, was comparable in size to that observed between strains carrying the ST or CH gene arrangements, and either alike or different at the Amy locus. Although some features of our results are puzzling, there is evidence that the Amy locus and others for which it serves as a marker have effects on mating behavior which include some degree of rare male mating advantage.
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Drosophila pseudoobscura females show a positive bias toward mating with males whose proportion in the population is low. They can perform this discrimination even when three strains of males are present. The olfactory recognition required for this discrimination entails a hierarchically ordered recognition system and a natural unit of olfactory strength.
With few exceptions, previously published experiments documenting ethological isolation between Drosophila populations have used young virgin females. We have observed directly females of Drosophila paulistorum semispecies in choice experiments with both homogamic and heterogamic males. Aged females' sexual selection did not differ from that of young females. Previous heterogamic copulatory experience did not change the degree of sexual isolation; however, females with homogamic copulatory experience showed a significantly higher preference for homogamic males.
The pole cells of young D. paulistorum embryos are destined to form the germinal cells of both male and female imagoes. In addition, specialized portions of the midgut may be derived from pole cell progenitors. In this initial study of their embryogenesis by means of electron microscopy, various stages of pole cell development are shown in both non-hybrid (potentially fertile) and intersemispecific hybrid (potentially sterile as males) materials. Originally, approximately 5 or 6 cells emerge to form the early polar cap and subsequently divide asynchronously until the 35-50 cells of the late polar cap are derived. Unlike other Drosophila species, however, mycoplasma-like symbionts, apparently an hereditary infection, have been traced to locations within the cytoplasm of these pole cells. They are depicted as arriving there after transmission via the egg cytoplasm, implicating this as their probable route of entry into the future germinal tissues of adult flies. It is postulated that these microorganisms function as an infectious reproductive isolating mechanism fostering hybrid male sterility between D. paulistorum semispecies.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Male hybrids from Mesitas and Santa Marta (Colombia) strains of Drosophila paulistorum are sterile. Homogenates of males belonging to these strains and from the hybrids were injected into Mesitas or Santa Marta females, which were crossed to males of their own strains, so that their progenies were genetically nonhybrid. Nevertheless, some of the males from these progenies were sterile. Male progenies of females that were injected with homogenates from males that disagreed in the source of cytoplasm with the recipients were sterile. No sterility was induced if the donors and the recipients had similar cytoplasm.