[TRANSFORMATIONS OF LIFE CYCLES IN THE EVOLUTIONARY HISTORY OF TRYPANOSOMATIDS. ENDOTRANSFORMATIONS AND ABERRATIONS].

Endotransformations and aberrations of the life cycle in the evolutionary history of trypanosomatids (Kinetoplastea: Trypanosomatidae) are analyzed. We treat the term "endotransformations" as evolutionarily fixed changes of phases and/or developmental stages of parasites. By contrast, we treat aberrations as evolutionary unstable, periodically arising deformations of developmental phases of trypanosomatids, never leading to life cycle changes. Various examples of life cycle endotransformations and aberrations in representatives of the family Trypanosomatidae are discussed.

[Light- and electron-microscopic study of pelobiont Pelomyxa secunda (Gruber, 1884) comb. nov. (Archamoebae, Pelobiontida)].

Morphology of a pelobiont Pelomyxa secunda (Gruber, 1884) comb. nov. was investigated at light- and electron-microscopical levels. Locomotive forms are elongated or cigar-shaped. The size of active forms varies from 200 to 300 µm. Larger individuals (up to 400 µm) are not able to directed movement. Organism can produce short, usually finger-shaped hyaline pseudopodia at the frontal side or laterally. The cell coat is represented by amorphous glycocalix, up to 300 nm in thickness. A thin periphery cytoplasmic zone is deprived of any organelles, vacuoles, endocytobionts and other inclusions and separated from main cytoplasm by a layer of arranged microfilaments. P. secunda is multinucleate organism; nuclei are of granular type. The nucleolar material is represented by two forms of discrete structures differing in size and electron density. Two or three layers of short microtubules organized in the parallel arrangement are associated with outer side of the nuclear envelop. P. secunda possess two types of obligate prokaryotic endocytobionts lying in individual symbiontophoric vacuoles. Undulipodia, kinetosomes and root microtubular derivatives are not observed in P. secunda cells as well as any developed cytoplasmic microtubular cytoskeleton.

[TRANSFORMATIONS OF LIFE CYCLES IN THE EVOLUTIONARY HISTORY OF TRYPANOSOMATIDAE. EXOTRANSFORMATIONS].

The present review is devoted to the analysis of exotransformations of life cycles in the evolutionary history of trypanosomatids (Kinetoplastea: Trypanosomatidae). Exotransformations are treated as processes associated with the transition of a trypanosomatid to a new host. The result of these transformations comprises both the inclusion of new hosts in life cycles of parasites and also epy formation of parasitic systems de novo. It is shown that exotransformations are one of the main modi in the evolution of trypanosomatids. Different examples of exotransformations of life cycle in all the taxonomic groups of Trypanosomatidae are given.

[TRANSFORMATIONS OF LIFE CYCLES IN THE EVOLUTIONARY HISTORY OF TRYPANOSOMATIDS. MACROTRANSFORMATIONS].

The review concerns analysis of life cycle macrotransformations in the evolutionary history of trypanosomatids. The term "macrotransformations" stands for evolutionary processes leading to the establishment of heteroxenous and secondary homoxenous life cycles within Trypanosomatidae. There were three direct macrotransformations in the evolution of the group resulting in the rise of heteroxenous genera Leishmania, Trypanosoma and Phytomonas, and one case of reverse macrotransformation in trypanosomes of T. (b.) brucei group. The issues of the origin, diversity and phylogeny of taxa whose emergence resulted from macrotransformations of life cycles of homoxenous trypanosomatids.

[Reisolation and redescription of pelobiont Pelomyxa paradoxa Penard, 1902 (Archamoebae, Pelobiontida)].

Morphology of a pelobiont Pelomyxa paradoxa Penard, 1902 was investigated at light- and electron-microscopical levels. Locomoting cells are cigar-shaped. The cells produce many hyaline pseudopodia of digital and conical form at lateral sides of the body. The organism has a pronounced hyaline bulbous uroid with broad peripheral zone of hyaloplasm and many conical hyaline villi. There is a thin layer of amorphous glycocalix at the cell surface. "Structure" and food vacuoles of different size are very abundant in the endoplasm. Two different species of prokaryote endocytobionts are peculiar for P. paradoxa. Uninucleate stage dominates in the life cycle of P. paradoxa. Usually there are no more than 10-12 nuclei in multinucleate forms of P. paradoxa. Pelomyxae nuclei are closely surrounded by thick multilaminar layer and additionally by one more layer, which is formed by small vesicles with electron-dense content. Several irregular-shaped nucleoli are situated at the nucleus periphery. Inside the nucleoli, and sometimes directly in nucleoplasm the small round bodies are revealed, these bodies being formed by tightly packed electron-dense fibrils. Many non-motile flagellae are located mainly in the uroidal zone of the cell. Pronounced lateral root and 50-60 radial microtubules originate from the electrone-dense muft around the kinetosome. All elements of the rootlet system of flagella are limited by peripheral layers of cytoplasm. P. paradoxa occupy an intermediate position between two groups of species of Pelomyxa genus--P. gruberi + P. prima and P. palustris + P. stagnalis + P. belewski, which differ greatly by the organization of their flagella basal apparatus.

[Homoxenous trypanosomatids from true bugs Pyrrhocoris apterus (L.) in the north of the Pskov region].

In the north of the Pskov region (58 degrees 35' N, 28 degrees 55' E) the appearance of a single colony of true bugs Pyrrhocoris apterus has been recorded. Dissection of 95 individuals from this colony revealed 100% prevalence of infection with homoxenous trypanosomatids. In 3% of the cases intestinal infection was accompanied by hyperinvasion into the salivary glands and hemolyph of the hosts. Analysis of trypanosomatid morphotypes demonstrated mixed infections in all studied P. apterus individuals. At least 4 forms of promastigotes along with epimastigotes, choanomastigotes and amastigotes were found. The distribution of the trypanosomatid morphotypes over all intestinal parts as well as salivary glands and hemolymph was investigated. Three isolates of the flagellates were deposited into the living cultures collection of the laboratory of Protozoology of the Zoological institute of the Russian Academy of Sciences.

[Comparative morphology of the subphilum Conosa Cavalier-Smith 1998].

Comparative analysis of archamoebae and slime molds morphology revealed that this organisms have a marked similarity in organization of locomotive forms, structure of glycocalix and also in organization of nuclear and flagellar apparatus. A possible scheme of formation the modern diversity of Conosa group was proposed.

[Morphology of Mastigamoeba aspera Schulze, 1875 (Archamoebae, Pelobiontida)].

The morphology of Mastigamoeba aspera, a type species of the genus Mastigamoeba Schulze, 1875, has been investigated at the light- and electron-microscopical level. Motile individuals are oval or peach-shaped. Motile flagella is situated at the anterior end of uninucleate cells. During locomotion, the surface of mastigamoebes forms many conical or finger-shaped hyaline pseudopodia, wereas bulbous uroid is often formed at the posterior end of the cell. Micropopulations of M. aspera consist of uninucleate flagellate forms as well as multinucleate aflagellate ones. There is a thick layer ofglycocalix on the cell surface where many rod-shaped bacterial ectobionts live. The nucleus is vesicular with spherical central nucleolus. The flagellar apparatus of M. aspera is connected with nucleus to form so called kariomastigont. A single kinetosome is associated with many radial microtubules and a lateral root. A distinct microtubule organization centre (MTOC) is situated at the basal part of the kinetosome. Microtubules of the nuclear cone are connected with the MTOC. This microtubules take part in the formation of kariomastigont. The axoneme has a standart set of microtubules 9(2)+2. Digestive vacuoles are the main component of the cytoplasm of M. aspera. Beside, many light-difracted granules and glycogen bodies were found in the cells. Mitochondria, dictyosomes of the Golgi apparatus and microbodies were not revealed in the cytoplasm of M. aspera.

[Investigation of causes of the conflict between taxonomy and molecular phylogeny of trypanosomatids by the example of Leptomonas nabiculae podlipaev, 1987].

Results of study of Leptomonas nabiculae using various molecular markers and different material (cultures D2 et Nfm2) contradicted each other and taxonomic position of this species. We investigated morphology of the cells in these cultures as well as in hapantotype of L. nabiculae and those of L. peterhoffi and L. occidentalis that had been described from the same host species. We also reconstructed 18S rRNA gene phylogeny using sequences from both cultures. The D2 culture according to its morphology and phylogenetic position revealed to be a Crithidia that had accompanied L. nabiculae in a mixed infection. We named it Crithidia dedva. The cells in the hapantotypes of the three Leptomonas species and those of the Nfm2 culture represent a single species that is a Herpetomonas (H. nabiculae) judging by morphology and molecular phylogeny. We also showed that the sequence of 18S rRNA gene that had been formerly determined represents a chimaera. This had resulted in the wrong position of this species on the phylogenetic tree that had contradicted results of the analysis of 5s rRNA gene.

[Light- and electron-microscopical study of Pelomyxa flava sp. n. (archamoebae, pelobiontida)].

Using light and electron microscopy, the morphology of a new species of pelobionts Pelomyxa flava was studied. The coverings of P. flava are represented by plasma membrane bearing the thick layer of weakly structured glycocalyx on its outer surface. Numerous flagella are often located on the tops of short conical pseudopodia. Kinetosomes of flagella reach a length of 0.9 microm and are hollow with a pronounced central filament. Rootlet system is represented by three groups of microtubules: the radial, basal and microtubules of lateral root. The transition zone is short and does not exceed the level of cell surface; the axoneme is characterized by an unstable set of microtubules. Trophic stages of P. flava life cycle are presented by binuclear cells; plasmotomy is performed at the tetranuclear stage. Nuclei have a granular structure. Fibrillar nuclear bodies were revealed in karyoplasm. The nuclei shell has a complex organization. On its surface, the outer membrane has a layer of electron-dense material which contacts with short microtubules, located in a row at the surface of the nuclear envelope. The bubbles and cisterns of endoplasmic reticulum, which are the derivatives of the nuclear envelope, are located outward from the microtubules. The presence of structural and digestive vacuoles and grains of glycogen was noticed in P. flava endoplasm. Three types of prokaryotic cytobionts were revealed. Large multi-membranous organelles reaching 5 pm in diameter were described for the first time. We discuss morphology and biology features of P. flava in comparison with the previously studied Pelomyxa species.

[Light- and electron-microscopical study of Pelomyxa stagnalis Sp. n. (Archamoebae, Pelobiontida)].

The structure of a new pelomyxa species was investigated with the use of light- and electron-microscope technique. Motile individuals reach 800 microm in length. There is a thin layer of amorphous glycocalix on the cell surface. Many non-motile flagellae are found mainly in the uroidal zone. The axoneme has a non-stable set of microtubules. There are no any special elements in the transition zone. A short kinetosome is about 150 nm long. A bundle of 15-20 microtubules starts from the one side of kinetosome and pass below the cell surface. Structure vacuoles are one of the main cytoplasm components of Pelomyxa stagnalis. Glycogen bodies are surrounded with flattened reticulum cisterns often containing electron-dense material. Two morphological distinct species if prokaryote endobionts were found in the cells of P. stagnalis. The number of nuclei in the cells of P. stagnalis reaches 50 or more. The nuclei are rounded by a two-layer envelope including a multilaminar layer and outer layer, which is formed by small vesicles often containing electron-dense material. One nucleolus is situated at the center of a nucleus. In the nuclei, often in connection with the nucleolus, there are bodies formed by electron-dense threads.

[On the problem of identification of homoxenous trypanosome cultures with the description of a new species Wallaceina podlipaevi sp. n. (Kinetoplastida: Trypanosomatidae)].

The type culture of Leptomonas peterhoffi Podlipaev, 1985 (stamm P-101) was examined using light and electron microscopy. The hapantotype of L. peterhoffi Podlipaev, 1985 was reexamined with a light microscope. As a result, a new species of homoxenous trypanosomes, Wallaceina podlipaevi, sp. n. was described.

[The morphological study of the cysts Pelomyxa palustris Greeff, 1874].

Pelomyxa palustris Greeff, 1874, is the only species of pelomixoid amoebas with the rest cysts in its life cycle. The morphology of the P. palustris has been studied by the light and electronic microscopy. Encystation of P. palustris under climatic conditions of North-West of Russia occurs within August-September. Rest cysts have a complex, trilaminar wall. Two inner lamina are the dense endocyst and the laminated mesocyst, thickness of each layer runs up to 0.6-0.7 microm. Thickness of the electron-dense ectocyst usually does not exceed 0.1-0.2 microm. The encystated cell of P. palustris has the unique structure. About 60 % of the cell volume are occupied by a huge vacuole placed in the center and filled up with the prokaryotic cytobionts. Different vacuoles, small vesicles of various nature, autophagosomes and lipid drops could be found inside that huge vacuole. The amoebae cytoplasm occupies the space in between endocyst's inner surface and the central vacuole. No any inclusions, prokaryotic cytobionts and most of cell organelles are absent in the cytoplasm. There are 4 large nuclei filled with relatively homogeneous karyoplasm lying in the cytoplasm. Nuclear envelope forms a lot of long tubular channels, running through the cytoplasm and lining the membrane of the central vacuole. Encysted pelomixoid stay in this state up until the beginning of excystation. Excystation of P. palustris in the studied region occurs in spring, during the latter half of April and the beginning of May. Cysts undergo complex morphofunctional changes, related to the reorganization of the wall and formation of young multinucleate amoebas. Only one wall lamina of the 3 initial ones is left up to the moment of excystation. The central vacuole endures ruination and its content penetrates into the cytoplasm. Pelomixoid nuclei divide twice. Prokaryotic cytobionts are localized in cytoplasm and in the perinuclear area. Young multinuclear species of P. palustris coming out of the cysts do not differ in their structure from the adult forms.

[Mitosis in the free-living flagellate Bodo saltans strain PS+ (Kinetoplastidea, Bodonida)].

The mitosis in the free-living flagellate Bodo saltans Ps+ with prokaryotic cytobionts in perinuclear space has been studied. The nuclear division in B. saltans Ps+ occurs by closed mitosis type without condensation of chromosomes. Two spatially separated mitotic spindles begin to form consistently at the initial stages of nuclear division. The spindle including about 20 microtubules appears first and later the second spindle with half the number of microtubules comes at the angle of 30-40 degrees. Both spindles rest their ends against the inner nuclear membrane and form 4 distinct poles. The microtubules of the first spindle are associated with 4 pairs of kinetochores, the microtubules of the second one are associated with 2 pairs of kinetochores. The divergence of the kinetochores towards the poles occurs independently in each spindle. The equatorial phase is not revealed in B. saltans Ps+. The poles of both spindles unite in pairs at the elongation phase of mitosis and form the integrated bipolar structure. At this stage of the nuclear division, the kinetochores reach the poles of subspindles and become indistinguishable. Then the nucleus takes the shape of a dumbbell. The inner nuclear membranes of just formed nuclei have layers of condensed chromatin characteristic of the interphase nuclei of kinetoplastidea. The daughter nuclei separate at the phase of reorganization. There are 1-2 prokaryotic endocytobionts in the perinuclear space of the interphase nuclei in B. saltans Ps+. The symbionts multiply during mitosis and their number reaches more than 20 specimens par nucleus.

[Leptomonas jaculum (Leger, 1902) Woodcock 1914: a leptomonas or a blastocrithidia?].

Flagellates Leptomonas jaculum, inhabiting the intestine of the water scorpion Nepa cinerea posses promastigote organization, typical of the genus Leptomonas. Nevertheless phylogenetic analysis of the 18S rRNA gene revealed that these trypanosomatids form a common phylogenetic clade with cyst-forming representatives of the genus Blastocrithidia. Morphological characters supporting the unity of the group Blastocrithidia + L. jaculum and the probability of including L. oncopelti in it are discussed.

[Development of cyst-like cells of the flagellate Leptomonas oncopelti in the midgut of the hemipteran Oncopeltus fasciatus].

The structure of cyst-like cells of Leptomonas oncopelti (Trypanosomatidae) found in the midgut of the bug Oncopeltus fasciatus (Lygaeidae) was examined with light and electron microscopy. The formation of "cysts" begins with an unequal division of active flagellates with promastigote configuration. Cytokinesis starts on the lateral side of the flagellate, and then the cleavage furrow moves toward the apical end of the cell. The anterior part of a smaller daughter cell, referred to as cell C1, remains associated with the flagellum of maternal promastigote. C1 divides twice to give rise first to two equivalent cells (C2), and then to four morphologically similar cells (C3). C2 join with each other, and afterwards C3 attach between themselves as well via short cytoplasmic outgrowths, which appear instead flagella. In the point of outgrowth attachment of only one C2 and then of only one C3 to maternal flagellum zonal desmosomes occur. C1--C3 of L. oncopelti are similar to so-called straphangers (cyst-like parasites attached to the flagellum of maternal promastigote) known in some species of the genera Leptomonas and Blastocrithidia. Basal bodies are present in C1 and C2 but not in C3. DNA fibrils in the kinetoplast lack their common circular configuration, they progressively condense to form a disordered mass. C3 chromatin becomes denser to acquire eventually a characteristic "labyrinthine structure" looking like a huge bundle of whorled filaments 3-5 nm width. Inside this bundle there are channels of 10-12 nm in diameter filled with karyoplasm. On becoming ovoid, C3 are separated from the maternal promastigote flagellum and differentiate into mature "cysts". Straphangers C1--C3 and mature "cysts" lack any visible outer extracellular protective envelope (cyst wall). Instead, these cells have a cortical complex made of a reinforced plasmatic membrane underlined by a layer of a dense granular cytoplasm free of subpellicular microtubules. The mature "cyst" endoplasm shows a high electron density, and because of this identification of the majority of cellular organelles is next to impossible. Nevertheless, in both C3 and mature "cysts" some unusual membranes are seen composed of two electron lucent layers, with a single electron dense layer in between.

[Light and electron microscopic investigation of Pelomyxa prima (Gruber, 1884) (Peloflagellatea, Pelobiontida)].

Cell organization of a multinuclear pelobiont Pelomyxa prima has been studied at the light and electron microscopic levels. Motile individuals demonstrate a characteristic drop-like or pyriform shape and reach 550 microkm in length. The cell cover is represented by a well-developed, morphologically differentiated glycocalyx 80-100 nm thick. The cytoplasm contains many structural vacuoles. The nuclei are of vertical type, numbering up to several nuclei in large individuals. Numerous cytoplasmic microtubules are associated with the external membrane of the nuclear envelope. Separate non-motile flagella are distributed throughout the cell surface, being more numerous in the posterior body end and uroidal zone of the protist. Basal bodies of the flagella are extremely long, being deeply immersed into the cytoplasm. These bodies are surrounded by a muff of electron-dense material, with numerous microtubules radiating from it. A compact bundle of microtubules starts from the base of a basal body axially into the cytoplasm. Besides, a band-like lateral microtubular rootlet is present. The number of microtubules in the axoneme of undulipodia is unstable. Neither mitochondria, nor Golgi complex were found. Two species of bacterial endocytobionts are present in the cytoplasm in considerable numbers.

[The description and laboratory cultivation of Leptomonas repentinus sp.n. ( Kinetoplastida: Trypanosomatidae)--a parasite of the water strider Gerris rufoscutellatus]. / Opisanie i laboratornoe kul'tivirovanie Leptomonas repentinus sp.n. (Kinetoplastida:Trypanosomatidae)--parazita klopa-vodomerki Gerris rufoscutellatus.

A new homoxenos trypanosomatide, Leptomonas repentinus sp. n., is described from the digestion tract of the water strider Gerris rufoscutellatus. The laboratory culture of L. repentinus has been obtained. Cultural stages of L. repentinus have been studied with TEM. The mitochondrion and kinetoplast have unusual structure. Large symbiont-like spherical bodies have been found in the mitochondrial matrix.

[Ultrastructure of the flagellate Cruzella marina (Kinetoplastidea)]. / Ul'trasruktura zhgutikonostsa Cruzella marina (Kinetoplastidea).

The ultrastructure of a marine, free-living heterotrophic kinetoplastid Cruzella marina was investigated with special attention being paid to the mitochondrion and flagellar organization. The flagellates have a polykinetoplastidal mitochondrion. Two flagella emerge from the pocket; one of these turns anteriorly being forward-directed, while the other is posteriorly directed to be adjacent to the ventral cell surface. The transition zone of both the flagella includes central filaments. The cytostome opens on the tip of the rostrum. The cytostome leads to the channel of cytopharynx, which penetrates the rostrum and proceeds into the flagellate body cytoplasm. The comparison of the relevant morphological and molecular data suggest that C. marina may arise early in the Kinetoplastidea lineage, before divergence of the majority taxa of the kinetoplastid flagellates.

[Cryptobia udonellae sp. n. (Kinetoplastidea: Cryptobiida) - parasites of the excretory system of Udonella murmanica (Udonellida)]. / Cryptobia udonellae sp. n. (Kinetoplastidea: Cryptobiida) - parazit vydelitel'noi sistemy Udonella murmanica (Udonellida).

A new cryptobiid flagellates, Cryptobia udonellae sp. n., is described from the excretory channels of Udonella murmanica. The body of flagellates is spindle-shaped. The flagellar pocket is subapical. Two flagella emerge from the pocket. One flagellum turns anterior and is forward-directed; the other flagellum is directed posterior and close to the ventral cell surface. The ventral groove is well developed. The cytostome opens just anterior to the flagellar pocket. The cytostome leads to the short cytopharynx. In the excretory channel of worms the flagellates C. udonellae sp. n. are attached to microvilli of epithelium or lay free in the lumen. Both flagellates have been studied with TEM. The unusual parasite system which involves organisms of four different phylums of animals has been described for the first time.