[Electron microscope studies on developmental stages of Theileria parva (Theiler, 1904) in the intestine of the tick Hyalomma anatolicum excavatum (Koch, 1844) (author's transl)].

The developmental stages of Theileria parva within the intestine of ticks were studied by electron microscopy. On the 2nd-4th day post repletionem (p.r.) the intestine of the ticks contained numerous stages, which were very similar to microgamonts and microgametes of haemosporidia. From these results it seemed likely that gamogony of Theileria parva takes place in the intestine of ticks, too. The microgamont-like stages were spear-head-like; they measured about 10.5 mum in length with a maximum diameter of about 2.1 mum in their middle region. These parasites, which were limited by a unit membrane, had a stiletto-like apex, several flagellar-like protrusions of about 3 mum in length and mostly two slender posterior protrusions. The stiletto-like structure was electron-dense and measured about 2.0 mum in length; at its base it appeared spongy consisting of coiled, fibrillar elements of about 20 nm in diameter. Up to 4 flagellar-like protrusions were found in cross sections originating near the base of the stiletto-like structure. At most, up to six microtubules were seen within these protrusions, which, however, at their free ends usually contained only two microtubules. Near the base of the stiletto-like structure two groups of additional microtubules began. One group ran beneath a third of the peripheral margin to the posterior cell pole. The other group was bundle-like arranged. In cross sections through the posterior slender protrusions of the parasite about 10 microtubules appeared in an irregular pattern. The slender posterior protrusions had nearly double dimensions of the flagellar-like protrusions.