A QUANTITATIVE STUDY OF ANAPHASE MOVEMENT IN THE APHID TAMALIA

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Abstract
Testes and embryos of T. coweni, isolated in paraffin oil, were used to study the anaphase movement in living spermatocytes and embryonic cells. The distance between kinetochores of separating daughter chromosomes as well as the length of the cell were measured with a camera lucida and plotted against time. In stained sections the length of chromosomal fibers and spindle as a whole was detd. and plotted against kinetochore distance. In secondary spermatocytes and embryonic cells the curve consists of 2 S-shaped components separated by a plateau. Comparison with measurements on fixed cells shows that the first part is correlated with a shortening of the chromosomal fibers, moving the chromosomes to the poles, while the spindle as a whole remains constant in length. The 2d phase coincides with spindle elongation (and cell elongation) with the chromosomal fibers remaining unchanged. In the primary spermatocytes only the spindle elongation takes place. The chromosomal fibers transmit the movement to the chromosomes but are of constant length throughout anaphase. This is an exceptional behavior. A study of first meiotic divisions in the hemipteran Protenor and homopteran Thelia showed that the anaphase movement is of the same type as in secondary spermatocytes and embryonic cells of the aphid. The data demonstrate that there are at least 2 independent factors in the anaphase movement of chromosomes, the shortening of chromosomal fibers and the elongation of the spindle body. The separation in time of these 2 processes appears to be correlated with the diffuse spindle attachment characterizing the forms analyzed.

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