The ovary structure, previtellogenic and vitellogenic stages in parthenogenetic species Dactylobiotus dispar (Murray, 1907) (Tardigrada: Eutardigrada)

The reproductive system of Dactylobiotus dispar consists of the ovary and the oviduct that opens into the rectum. The sack-like ovary is filled with the developing oocytes, which are assisted by the trophocytes. In D. dispar, the mixed vitellogenesis takes place. One part of the yolk material is produced inside the oocyte (autosynthesis), the second part is absorbed by micropinocytosis while the third part is synthesized in the trophocytes and is transported to the oocytes through the cytoplasmatic bridges. Moreover, rRNA, lipids and mitochondria are transfered from the trophocytes to the oocytes. The histochemical researches show that the reserve material accumulated in the oocytes contains proteins, polysaccharides and lipids.