Organization of the egg chambers in Hydradephaga (Insecta, Coleoptera-Adephaga) and its phylogenetic significance
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The structure of the ovaries in three representatives of Hydradephaga (Haliplus flavicollis, Gyrinus natator and Orectochilus villosus) and one of Geadephaga (Carabus variolosus) was studied. In all the investigated species the ovarioles are of the meroistic polytrophic type. Within ovarioles several egg chambers occur, clearly separated into two compartments: one occupied by nurse cells and the other by an oocyte. The analysis of serial semithin sections revealed that the clusters of the germ cells are branched and that there are always 7 nurse cells in the egg chambers in the examined Hydradephaga. In contrast, the number of nurse cells in Carabus variolosus egg chambers is variable and much greater (around 60). In addition, in the last species a few trophocytes were found containing 2 nuclei. In view of the results obtained the possible phylogenetic implications are discussed. A tentative hypothesis is proposed that a small and constant number of the nurse cells might be a plesiomorphic condition for the suborder Adephaga.
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M. K. Jaglarz, Department of Zoology, Institute of Zoology, Jagiellonian University, R. Ingardena 6, 30-060 Krakow, Poland. E-mail: email@example.com