Vital Staining of Insect Eggs by Incorporation of Trypan Blue

Abstract

MORPHOGENETIC movements which occur during the early stages of animal embryogenesis are difficult to study unless some kind of marking technique is used. In vertebrates vital staining of small cell patches¹ or application of charcoal powder² has permitted the construction of maps showing extensive morphogenetic movements during early embryogenesis. Similar techniques have proved useful for the study of morphogenesis in other animal phyla. There are, however, no reports on successful intra vitam staining of insect eggs. This may be because the protective covers of most insect eggs do not permit dyes to enter locally, while eggs deprived of their covers cease to develop. Morphogenetic movements taking place during the plasmodial stages³ of insect embryogenesis therefore had to be reconstructed from a series of fixed material^4–6 or were analysed by using local defects as markers^7,8 and by time lapse studies^7,9,10. Defect marking more than other techniques involves the danger of misinterpretation. Time lapse studies and investigations on fixed material share the disadvantage that only a limited range of structures located in the egg plasmodium can be traced satisfactorily, for example, nuclei or special inclusions of the cytoplasm; furthermore, work with fixed material is technically difficult and cinematography fails to reveal movements within bulky eggs sufficiently clearly. Renewed attempts to overcome these handicaps have produced a technique which, although far from being as versatile as vital staining in amphibians, serves to reveal the type and extent of movements within the whole egg plasmodium of the house cricket (Acheta domesticus L.) during germ band formation and anatrepsis.