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Keywords:

  • ovary;
  • ultrastructure;
  • primitive aphids;
  • Adelgidae;
  • phylogeny;
  • endosymbiotic micro-organisms

Abstract

The structure of ovaries has been analysed in advanced aphids only. In this paper we report the results of ultrastructural studies on the ovarioles of Adelges laricis, a representative of the primitive aphid family, Adelgidae. The ovaries of the studied species are composed of five telotrophic-meroistic ovarioles that are subdivided into a terminal filament, tropharium (= trophic chamber) and vitellarium. The tropharium houses trophocytes (= nurse cells) and arrested oocytes. The vitellarium consists of one or two ovarian follicles. The total number of germ cells (trophocytes + oocytes) in the ovarioles analysed varies from 50 to 92 and is substantially higher than in previously studied aphids. The centre of the tropharium is occupied by a cell-free region, termed a trophic core, which is connected both with trophocytes and oocytes. Trophocytes are connected to the core by means of cytoplasmic strands, whereas oocytes by nutritive cords. Both trophic core and nutritive cords are filled with parallel arranged microtubules. In the light of obtained results the anagenesis of hemipteran ovaries is discussed.