ORGANIZATION OF THE EGG CHAMBERS IN HYDRADEPHAGA (INSECTA, COLEOPTERA-ADEPHAGA) AND ITS PHYLOGENETIC SIGNIFICANCE

The structure of the ovaries in three representatives of Hydradephaga (Haliplus flavicollis Gyrinus natator and Orectochilus villosus) and o ne of Geadephaga (Carabus variolosus) was studied. In all the investig ated species the ovarioles are of the meroistic polytrophic type. With in ovarioles several egg chambers occur, clearly separated into two co mpartments: one occupied by nurse cells and the other by an oocyte. Th e analysis of serial semithin sections revealed that the clusters of t he germ cells are branched and that there art: always 7 nurse cells in the egg chambers in the examined Hydradephaga. In contrast, the numbe r of nurse cells in Carabus variolosus egg chambers is variable and mu ch greater (around 60). In addition, in the last species a few trophoc ytes were found containing 2 nuclei. In view of the results obtained t he possible phylogenetic implications are discussed. A tentative hypot hesis is proposed that a small and constant number of the nurse cells might be a plesiomorphic condition for the suborder Adephaga.