Zeitrafferfilmanalyse der Embryonalentwicklungin vitro der vivipar paedogenetischen GallmückeHeteropeza pygmaeaWent, Dirk
doi: 10.1007/BF00575520pmid: 28304830
1.
In the paedogenetic gall midgeHeteropeza pygmaea, embryonic growth is at the expense of maternal tissues. The possibility of culturing egg folliclesin vitro throughout the entire period of embryonic development allowed the filming of embryogenesis. In the present paper development, growth and degeneration of egg folliclesin vitro (at 25° C) are analysed by time-lapse film.
2.
During development of the mature egg follicle up to germ band formation, the yolk globules undergo alternative periods of oscillation and rest within the yolk syncytium. During the periods of time in which the yolk globules are at rest, cleavage divisions take place. All egg follicles analysed showed 13 resting periods which corresponded to the 13 cleavage divisions. A comparison with other investigations indicates, that oscillation of the yolk globules is not required for the migration of the nuclei, but is connected with a special function of the yolk syncytium in paedogenetic gall midges.
3.
From the 1st until the 6th cleavage division the average duration of the mitotic cycle decreases from 75 to 50 minutes; from the 6th until the 13th cleavage division it increases to more than 3 hours.
4.
Blastokinesis, i. e. germ band extension and germ band retraction, in all probability is the consequence of autonomous movements of the germ band and not of a morphogenetic effect of the yolk syncytium.
5.
Egg follicles from different preparations show varying rates of development and growth whereas egg follicles within one culture drop develop and grow with the same rate although they may not be at exactly the same stage of development.
6.
In certain stages of development (cleavage, germ band retraction and dorsal closure) the increase in length of the egg follicle is discontinuous. During germ band retraction many egg follicles show up to 7 elongations and contractions, which may amount to as much as one fifth of the egg follicle length. The period of time of one elongation-contraction cycle is between 1 1/4 and 2 3/4 hours and increases by 1/4 hour with each new cycle. At the same time as the egg follicle length increases, its width decreases and vice-versa, suggesting that the increase in volume is continuous.
7.
Measurements of two egg follicles at the blastoderm stage revealed rhythmic fluctuations in length which amounted to no more than one fiftieth of the total egg follicle length. There may be as many as 60 such fluctuation cycles, each of which has a constant period of about 15 minutes. The endogenous process underlying these fluctuations is obscure.
8.
The egg follicles which degenerate in culture are generally the smaller and less developed ones in any given preparation; however, until their sudden degeneration, they show the same rate of growth and development as the non degenerating egg follicles.
9.
The extraordinary mode of paedogenetic egg development ofHeteropeza is interpreted as a displacement of embryogenesis into oogenesis.
Untersuchungen zur Entwicklung von Ganz- und Teilimplantaten der Flügelimaginalscheibe vonEphestia kühniella ZRahn, Peter
doi: 10.1007/BF00575521pmid: 28304831
1.
After implantation of an imaginal wing disc a mirror-image duplication of the disc is formed, starting with the development of a fold at the back edge of the basic region of the implanted wing disc.
2.
After implantation of an imaginal wing disc the host's pupation is delayed, the duration of the delay diminishing with the age of the regenerate.
3.
Implanted parts of wing discs also duplicate. In this case, too, the duplication starts with the formation of a fold in the basal region.
4.
No regenerate is formed, if the implant comprises no material from the basic region. Missing distal parts are not replaced during the host's phase of growth; they are, however, replaced during the phase of the prepupa.
5.
If the implant contains material from the basic region, a regenerate always develops. If the basic region is complete, a whole wing disc is regenerated; if it is not complete, only a duplicate of the implant is formed.
6.
Not before the 4th day is the regeneration fold finally determined.
7.
The regenerate of the implant always consists of fewer cells than a regenerate of the same age in the host.
8.
Implanted duplications do not lead to regeneration. On division of such a duplication along its axis of symmetry two new mirror-image duplications are formed (Verklonung).
9.
Implanted wing discs which have been incised down into the basic region can give rise to a treble formation besides a normal regenerate. Transplanted treble formations do not duplicate; they only form a normal regenerate.
10.
The transplantation of the upper layer of cells leads to the formation of two complete imaginal wing discs. A transplant from the lower layer of cells only duplicates itself.
11.
The formation of lacunae is limited to the upper layer of cells.
12.
Metamorphosed mirror-image duplications are not inverted. The regions which produce the articular portions are determined by implanted parts of wing discs.