[First analysis of ooplasmic flows and their structural bases during cleavage ofPimpla turionellae L. (Hymenoptera) : I. Light microscopic-anatomical alterations in egg architecture in coincidence with time lapse findings].

Investigations are based on findings of Wolf and Krause (1971). Further advances in knowledge of ooplasm flows over the entire egg were obtained by slow time lapse micrographs. 1. We succeeded in filming the first reaction of eggs to fixation solution.Specific fixation reactions corresponding to the different phases at ooplasm motion indicate additional characteristics of dynamic potentialities in the egg. Osmium-bichromat solution does not cause fixation reactions. The microscopic-anatomical finding therefore correctly reproduces the situation in ooplasm in the moment of fixation. The movements, visible in time lapse micrographs taken before and after the beginning of fixation were recorded on micro-kymograms. The typical ooplasm flows coinciding to the different phases of mitosis and structural alterations in the ooplasm could be exactly determined by 77 individual lapses. 2. Each phase of mitosis is accompanied by typical movements in the ooplasm. As first maturation division in the anterior pole region nears completion, amixing motion begins in the posterior half of the egg and gradually spreads over the entire egg. As the mixing motion comes to an end, the egg is clearer and possesses a periplasm. During the first maturation division, the central and marginal plasm begin to flow weakly in opposite directions within the anterior third of the egg. 3. Thefirst unipolar flow begins with the end of the second maturation division. This and the following unipolar flow, running from the anterior to the posterior pole, are completing within a few minutes. The first unipolar flow and occasionally the second as well initiate not only in the maturation plasm but also in the posterior half of the egg. The strongersecond unipolar flow leads to cleavage, because the syncarion is shifted within it into the cleavage center. 4. The first cleavage divisions can be distinguished as pulses within thetransfer flow. This flow accompanies the energid group into the fontain flow initiation region, where the differentiation center for germ layers and segmentation is also localized. The pulsation point in the transfer flow indicates the position of the energid group, which reaches the fontain initiation region with 8-32 nuclei. 5. In this region, between 74-66%, the two fontain flows begin, moving in oppositely directed coincident flow pulsations towards both ends of the egg. These flows are correlated with the bipolar energid distribution to both egg poles. Thefront of the migrating energids is situated in the fontain flow front, which is recognizable by euplasmic streaks in sections. Within the energid group is a space containing vitellophags; the remaining contents of this space do not show a specific coloring and therefore are unknown. 6. The phases of the fontain flow are correlated in time with the phases of mitosis, between two pulses: pro- and metaphase, slow beginning phase: anaphase; quick mid-phase: telophase; slow ending phase: interphase. Eggs with the fourth or fifth flow pulsation have mitosis phases in three zones along the egg axis. This arrangement is possibly due to the bipolar motion during the fifth pulsation of the fontain flow toward the posterior pole. This bipolar motion, the posterior starting point of first unipolar flow, and the intensive mixing motion in the posterior part of the egg are interpreted as the visible effect of dynamic factors of aposterior initiation region. The investigations have produced the basis for experiments in creating different density gradients within the egg, with the aid of which we intend to search for the structural basis of ooplasmic dynamics.