Endocytobionts in Dermacentor reticulatus ticks (Ixodidae): an electron microscope study.

Endocytobionts (ECBs) were detected in the ovaries of Dermacentor reticulatus. Their developmental cycle is directly related to the developmental stages of tick oocytes. Two basic forms of ECBs occur in tick cells, i.e. dense forms, occurring singly or in aggregates situated free in the cytoplasm of host cells, and the light forms which are larger, pleomorphic and always situated inside vacuoles of host cells. The light forms occur together with dense forms in all oocytes. The dense forms occur freely and independently in funicular cells of the oocyte, the epithelial cells of oviducts, and additionally in the cells of the Malpighian tubules. A probable function of ECBs in the tick host is discussed.