[The fine structure of the cortical zone in the gregarine Bothriopsides histrio (Eugregarinida: Actinocephalidae)].

Attached and non-attached trophozoites of the septate gregarine Bothriopsides histrio were found in the intestine of the freshwater beetle Acilius sulcatus. Circular folds in the border between proto- and deutomerites and longitudinal striation, running along the entire body of the parasite, were revealed in an optical microscope. Our studies have demonstrated that circular folds, forming a specific collar, are formed of ecto- and endocytes. The longitudinal striation is represented by overdeveloped folds developed by the epicyte and the ectocite. Numerous typical epicite folds were observed over the entire cell surface. Additionally, the symbiosis between gregarine cells and bacteria was revealed.

[Morphology of Urospora chiridotae (Sporozoa: Gregarinomorpha: Eugregarinida) from sea cucumber Chiridota laevis (Echinodermata: Holothuroidea: Apoda)]. / Morfologiia gamontov Urospora chiridotae (Sporozoa: Gregarinomorpha: Eugregarinida) iz goloturii Chiridota laevis (Echinodermata: Holothuroidea: Apoda).

Several morphological forms (morphotypes) of Urospora chiridotae gamontes are found in White Sea holothuroid Chiridota laevis. All these morphotypes are differed by localization in the body of host, form and cytological features. The gregarines are situated in several host biotopes, such as blood vessels, intestine and mesenteries. In the blood vessels elongate skittle-like cells supplied with long thin cytopillia are observed. On the external surface of the intestine spherical gregarines are found. These parasites commonly covered with one layer of coelomic epithelium's cells. In some holothuria intratissue spherical cells of parasites located in intestinal epithelium are presented. Both of these types of parasites lack cytopillia, and folds or ridges on its surface. On different mesenteries, connections between intestine and body wall, and also on intestine elongate ounce-shaped cells and gamontocysts are observed. These cells are situated on the apices of finger-like processes of the intestine and mesenteries surface. Ounce-shaped gregarines have cytopillia shorter than in skittle-like gregarines. The differences between morphotypes of Urospora chiridotae are probably caused by different environmental conditions. In the narrow rift of blood vessel elongate cells are developed. The cytopillia may serve for making more or less wide space around gregarines, which is necessary for food uptake. Spherical cells surrounded by host's cells and have the form typical for tissue parasites. In the wide coelomic cavity where convection of liquid proceeds better than in blood vessel, ounce-shaped gregarines with short cytopillia are developed. We found only typical for Urospora chiridotae ovoid oocysts with dissimilar ends, anterior collar and spine-like posterior end. Thus, the all above-mentioned morphotypes undoubtedly belong to the same species. The relationships between defense host cells and the different morphotypes of trophozoites are variable.