[Characterization of Cestoda tissue organization].

The comprehensive ultrastructural characteristic of the somatic tissues for the class Cestoda is presented on the basis of own and literary data: muscular, nervous systems, parenchyma and epithelial tissue. The composition of the cambial systems is summarized and characteristic of its organization are revealed in comparison with other classes of flat worms.

[Interaction of the uterus and developing eggs in cyclophyllidean cestodes with different fecundity].

The interaction of morphological changes of the uterus and fecundity of the strobilus of cestodes has been investigated. It is shown that cestodes with maximal fecundity have different and highly effective ways of supplying eggs with nutrients. It is noted that differences in fecundity of cestodes depend not only on their strategy of reproduction, ecology, and complexity of life cycles but also on the complexity of interactions between the uterus and the developing eggs.

[Structure of the glial cells in the nervous system of parasitic and free-living flatworms].

This study is devoted to ultrastructural and immunosytochemical investigation of the nervous system in parasitic and free-living platyhelminthes to learn if glial cells exist in the nervous system of flatworms. We described the ultrastructure of different types of glial cells and the peculiarities of myelinization of gigantic axons; immunoreactivity to the S100b protein is revealed. Comparative analysis of the glia structure of annelids and platods is given; structural, functional, and evolutionary aspects of myelinization of gigantic axons, which are revealed in cestodes, are discussed.

[The symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts].

The indigenous symbiotic microflora associated with the tegument of proteocephalidean cestodes and the intestines of their fish hosts has been investigated in morphological and ecological aspects. The indigenous microflora associated with the cestode tegument consists of the nannobacteria population, which was present obligatorily on the surface of tegument, and the "deep microflora". The deep microflora associates with some few species of parasites only. Each individual host-parasite micro-biocenosis includes specific indigenous symbiotic microorganisms, with the differing microfloras of host intestine and parasite. Physiology, biochemistry and/or diet of hosts apparently influence on the symbiotic microflora's structure of parasites. The least bacteria abundance and diversity of their morphotypes were observed in the parasites from baby fishes. The diversity and abundance of bacteria were increased with the fish host ageing and the formation of the definitive structure of its intestine. It is an evidence of the gradual invading of the intestinal parasites (cestodes) tegument by bacterial cells. The invading is realized on the base of the microflora that was present in the food of fish host. The symbiotic microflora has specific morphological features, can regulate the homeostasis of the cestodes and fish hosts and also can maintain equilibrium of alimentary and immune interrelations in the host-parasite system.

[Indigenous microflora associated with the tegument of Triaenophorus nodulosus (Cestoda) and the intestine of its pike host].

Investigations of the indigenous microflora associated with the mucous intestines of fish and its cestode parasites have been for the first time carried out using the methods of transmission and scanning electron microscopy. New data on the bacterial biodiversity in the cestode and its fish host are obtained. Nanobacteria and spirochaetes are for the first time revealed in a fish host together with the previously known bacteria forming the intestinal microflora of fish. Spirochaetes were shown to be associated with the intestines of a pike host only, while nanobacteria cover abundantly the surface of the apical parts of the intestinal microvilli and the apical parts of the microtriches in the cestode tegument. The similarity of the bacterial floras associated with the apical surface of the parasite tegument and the intestine of the host should be noted. At the same time, deeper bacterial communities represented by obligate symbionts are specific. Thus, there is a normal indigenous microflora in cestodes, associated with the tegumental surface. This symbiotic microflora has specific morphological features and provides the balance of relations in the parasite-host system.

[Fine structure of the female reproductive system in Sobolevicanthus gracilis and Cloacotaenia megalops (Cestoda: Cyclophyllidea)]. / Tonkoe stroenie zhenskoi reproduktivnoi sistemy u Sobolevicanthus gracilis i Cloacotaenia megalops (Cestoda: Cyclophyllidea).

The fine structure of the female reproductive organs and ducts in two cyclophyllidean cestodes was studied by transmission electron microscopy. All the studied ducts (vitelline, fertilization and vaginal ducts, and oviducts) as well as the uterine and ootype walls have the luminal surface elevated to form apical cytoplasmic lamellae and are surrounded by bands of circular muscules, which are attached to the basement layer. The structure of the studied ducts epithelium corresponds to the pattern described in other ducts of the cestode genital system, namely a nucleate syncytial layer. An exception is the vagina Sobolevicanthus gracilis, in which the surface is lined with not numerous atypical microtriches. The comparison of our results and the data reported for other species is given. It is found out that in different species of cestodes forming oligolecital eggs, there are observed various uterine structures and diverse contacts between the eggs capsules and the uterine epithelium. The formation of special structures and contacts is the evolutionary way from the extrauterine type to more progressive intrauterine type of embryo development in cestodes.

[The parenchymal cellular composition and extracellular matrix in ontogenesis of Triaenophorus nodulus (Cestoda)]. / Kletochnyi sostav parenkhimy i mezhkletochnyi matriks v ontogeneze Triaenophorus nodulus (Cestoda).

The cellular composition of parenchyma was studied in the ontogenesis of Triaenophorus nodulosus and it was shown that the specialized parenchymal cells was absent. The extracellular matrix fibrils were synthesized successively by the tegumental cytons and muscle cells. The coracidium basal matrix consisted of electron-light and electron-dense layers, and the reticular layer appeared at the procercoid stage. Reserve nutrients were accumulated by the musculocutaneous sac elements at the procercoid stage and, later, by the glandular and tegumental cells. It has been proposed that the parenchyma as an independent histological unit is absent, while the parenchymal organization is based on all specialized cellular elements that do not lose their typical features.

[Structure of the copulative apparatus of Sobolevicanthus gracilis (Cestoda: Cyclophyllidea)]. / Stroenie kopuliativnogo apparata Sobolevicanthus gracilis (Cestoda: Cyclophyllidea).

Fine structure of genital atrium, Furman body, distal region of vagina and sac cirrus were investigated. The broad polymorphism of surface microstructures (microtriches) in various parts of copulative apparatus has been revealed. The constitution of prostate glands, being the modified cytons of syncitial epithelium of the intrabursal section of spermaduct wall, is described. Based on obtained and reference data, a comparative morphological analysis of copulative apparatus organization in lowest and highest cestodes was carried out. The hypothesis suggests that evolution of its organization was connected with the reduction of the muscular elements and simultaneous improvement of their managing, their isolation from surrounding parenchyma and development of supporting connective tissue elements. It is shown, that Fuhrmann's body has its own developed muscular system armed with power microtriches and being capable to evaginate into the distal region of vagina. It is supposed that S. gracilis obtains of two different ways of copulation in: by means of cirrus that executes the cross fertilization; and by means of the additional copulative formation--Furman body, which guarantees the self fertilization of worms.