[The movement pattern during cleavage in artificially activated eggs ofPimpla turionellae (Hym.)].

The early embryonic development ofPimpla is characterized by a complicated temporal and spatial pattern of ooplasmic movements detected in time-lapse films made during cleavage. The modified movements observed after the architecture of oviposited eggs had been altered artificially by centrifugation indicated that there are different dynamic systems for ooplasmic streaming, contractions, and nuclear migration. The discovery that unlaid, explanted oocytes ofPimpla can be activated by mechanical deformation provided a new way of studying alterations of egg architecture, nucleocytoplasmic interactions, and the control of morphogenetic processes during cleavage and blastoderm formation.

Artifical rearrangements of insect ooplasm caused by fixation, and their microkymographic recording.

Time-lapse photomicrographs of eggs from the Ichneumonid waspPimpla and from the gall midgeWachtliella reveal that during fixation the ooplasm performs excessive streaming movements when conventional fluids such as Bouin's or Dubosq-Brasil's are used. InWachtliella, intravitelline cleavage may continue for two mitotic cycles during fixation. The cytoplasm of individual egg regions may become displaced up to 45% of the egg's length inPimpla, and up to 14% of the egg's length inWachtliella.

[Analysis of ooplasmic flows and their structural basis during cleavage ofPimpla turionellae L. (Hymenoptera) : III. Time lapse analysis of the development of centrifuged eggs].

Films ofPimpla eggs in which three different density gradients were produced (Nuss, 1974) made it possible to analyse the dynamic conditions that form the basis for the correct course of cleavage, of ooplasm movements and the distribution of energids. The results of sublethal stresses on the eggs led to the postulate that there is a system of factors which are arranged in a cylindrical wall in the central plasm flowing system, linked with the marginal streaming in opposite direction (Bruhns, 1974). Centrifuged eggs developing normally do not show any visible change in longitudinal streaming or in energid migration, as a result of the different stratification after spinning or after swinging at a short distance as well further from the rotational axis.

[Analysis of ooplasmic flows and their structural bases during cleavage inPimpla turionellae L. (Hymenoptera) : II. Strain of egg architecture by different acceleration gradients].

In the egg ofPimpla turionellae L., three density gradients are produced by different methods of centrifugation. In spinning, the egg is rotated about its own long axis, so that the lightest egg material is collected in a central column (radial stratification).