Modifications volumetriques et ultrastructurales des corpora allata du lepisme Thermobia domestica (Pacard) (Thysanura : Lepismatidae) au cours des cycles biologiques

Abstract

During the moulting and reproductive cycles, which coexist in adult females of the primitive insect Thermobia domestica, the corpora allata (CA) undergo periodical changes: their volumes and numbers of cells are lower at the beginning and at the end of each moulting cycle, and higher about the middle. However, the nucleo-cytoplasmic ratio does not undergo significant variations. An ultrastructural description of the CA cells is given for the first time in a lepismatid. The glandular cells, which are all similar, undergo 2 different stages: the so-called “clear cells” present at the beginning and the end of the moulting cycle, and the “dense cells” in the middle of the cycle. If there is no insemination at the beginning of each intermoulting period, the terminal oocytes are totally resorbed and most of the CA cells are in an intermediate stage between clear and dense cells. These data are discussed in relation to the probable variations in the physiological activity of the CA during normal adult cycles.