Early embryonic development of the dipteran insect Heteropeza pygmaea in the presence of cytoskeleton-affecting drugs

Abstract

Embryos of the paedogenetically reproducing gall midge Heteropeza pygmaea develop floating in the haemocoel of a so-called mother larva. The egg membranes remain permeable and the embryos increase in size during embryonic development by taking up nutrients from the haemolymph. Such embryos can be cultured in vitro, i.e. in haemolymph drops obtained from mother larvae. We tested the effects of several drugs known to interact with cytoskeletal elements on different stages of embryonic development, including cleavage and gastrulation. The drugs were added to the in vitro cultures and the effects were studied with time-lapse cine-micrography. Colchicine and vinblastine blocked cleaving eggs in metaphase stage and arrested yolk globule oscillation. In spite of such a block blastoderms once formed continued development through germ band formation and extension and also increased in size. Cytochalasin B did not affect the stage of cleavage; however, it inhibited gastrulation and subsequent morphogenetic processes and also prevented size increase. We conclude that (1) the functioning of microtubules is needed for yolk globule oscillation during cleavage interphases but not for the gastrulation processes subsequent to blastoderm formation and (2) microfilaments do not play an important role in cleavage, at least not for the orderly succession of the cleavage divisions, but are essential for the morphogenetic movements associated with gastrulation. We suggest that during cleavage a limited stock of microtubules and their precursors is responsible for both transport of chromosomes during mitoses and translocation of organelles during interphase. Yolk oscillation seems to be a secondary effect and of minor or no importance for the normal course of embryonic development.

From egg to pole cells: Ultrastructural aspects of early cleavage and germ cell determination in insects

“…Several drugs known to interact with cytoskeletal elements have been used in Drosophila (Foe and Alberts, 1983;Kellogg et al, 1988;Zalokar and Erk, 19761, in the nonpaedogenetic gall midge Wachtliella (Wolf, 19781, and in the paedogenetically reproducing gall midge Heteropeza (Kaiser and Went, 1987). In the latter, no cytaster has been found so far, but during periods of interphase, microtubules are very numerous throughout the cleaving egg (Junquera, 1985).…”

“…Moreover, these studies have been frequently restricted to certain selected egg regions (for review see Zissler and Sander, 1982). Attempts at analyzing the entire cytoarchitecture of the newly laid egg and the early developmental stages (i.e., cleavage to early blastoderm) by TEM have been made so far in certain species of the fruitfly, Drosophila (Engstrom et al, 1982;Fullilove and Jacobson, 1971;Fullilove et al, 1978;Hay et al, 1988a;Kobayashi and Okada, 1989;Mahowald, 1962Mahowald, , 1963aMahowald, ,b, 1968Mahowald, , 1971aMahowald et al, 1976Mahowald et al, , 1979aMahowald et al, ,b, 1981Mahowald et al, , 1983Okada, 1986;Okada and Kobayashi, 1987;Okada and Waddington, 1959;Sanders, 1975;Swanson and Poodry, 1980;Ueda and Okada, 19821, in the cecidomyiide gall midge, Heteropeza pygmaea (Fux, 1975;Junquera, 1983Junquera, , 1985Kaiser and Went, 1987;Meats and Tucker, 1976), in the chironomid midge, Smittia spec. (Zissler, 1987;Zissler and Sander, 1973, 1977 and in the domesticated silkmoth, Bombyx mori (Miya, 1978(Miya, , 1984(Miya, , 1985Takesue, 1985;Takesue and Keino, 1982;Takesue et al, 1985).…”

The Spindle Assembly Checkpoint Functions during Early Development in Non-Chordate Embryos

“…As already mentioned, colchicine treatment blocks cyclin B degradation in clam embryos during first mitosis [13], and addition of nocodazole blocks nuclear division in embryos of another mollusk, the gastropod Ilyanassa obsoleta [58]. Similarly, treatment with colchicine delays nuclear division at least for the length of one cell cycle in embryos of the fruit fly D. melanogaster [41] and in binucleated embryos of the gall midges Wachtliella periscariae [59] and Heteropeza pygmaea [60].…”