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Ultrastructure of colourless predatory Spiromonas angusta was studied. Pellicle of the cell consists of the external membrane and two membranes of endoplasmic reticulum. Some micropores represent invaginations of plasmalemma. Vegetative stages have two flagella: one flagellum begins from a small flagellated chamber, the other begins directly from the body surface. Subpellicular system of microtubes deviates from the anterior end of the body. Conoid consists of 24—25 microtubes. Two bands of 4 microtubes pass near kinetosomes. Two bundles of narrow micronemae lie in the anterior part of the body, roptriae are not found. Large digestive vacuole lies in the hind end of the body. Reproduction of cells carries out in cysts surrounded by a thin membrane. The pattern of the structure of S. angusta corresponds fully to that of Sporozoa. On the basis of original and literary data members of the family Spiromonadidae Hollande, 1952 are separated into the subclass Spiromonadomorphina subcl. n. with the order Spiromonadida ordo n. in the class Perkinsemorpha Levine, 1978, the type Sporozoa.

The orientational behaviour of the imago of ticks in natural conditions is based on the optimal using of relatively primitive eyes with the development of a specifical mechanism of orientation. A statistical study of tracks of ticks together with the analysis of the optical system and functional possibilities of the eyes have made it possible for the author to suggest a model of orientational mechanism based on different signal meanings of increasing and decreasing of light intensity registered by the eyes from the direction of their main optical axes.

Ultrastructure of receptor endings, which are localized in the tegument of mature larvae and strobilae of 10 species of cyclophyllids, has been studied. A great morphological variety of endings, which in total enable the organism to perceive the whole complex of physical and chemical parameters of the medium, has been found out. According to cytomorphological criteria receptor endings are classified into three main types and 12 subtypes. Functional meaning of some endings is discussed.

Material and literary data on the occurrence of tetraphyllids in invertebrates and fishes as well as consideration of food links of hosts at all developmental stages of cestodes suggest that the life cycle of these cestodes is accomplished according to bixenic and trixenic developmental types. Modifications of life cycles are possible.

An ecological and parasitological investigation of benthic gastropods in the South-East region of the Barents Sea has been made for the first time. 14 species of parthenitae and trematode larvae have been found. The molluscs Margarites groenlandica, Solariella varicosa, Cryptonatica clausa and Neptunea despecta are highly infected. Maximum specific varietyof trematodes and the highest extensiveness of their infection of molluscs were marked at small depths in coastal waters, and in more seaward waters — on banks. Near the coast of the Kolguyev Island powerful seat of infection of sublitoral gastropods by microphallids of the group "pygmaeus" was discovered. It was shown that specific conditions of the South-East region of the Barents Sea are favourable for successful realisation of the trematode life cycles. Therefore, the infection of the benthic molluscs here exceeds the infection noted in more western regions of the Barents Sea.

Comparative study on effectiveness of intravenous and subcutaneous methods of infection of animals has shown that infection rate of helminths after the injection of equal dozes of cercariae under skin, into portal and femoral veins of golden hampsters does not differ significantly (42.6±4.2, 37.8±5.8 and 26.0±6.6 schistosomes, respectively). When using the above methods for cotton rats the infection rate was lower than that in golden hampsters. The most insignificant infection rate of parasites was recorded in both species after the injection of cercariae into the femoral vein. Results of the infection of golden hampsters with different dozes of cercariae have shown that with the increase of dozes of infectious material the infection rate of helminths rises during the experimental intestinal schistosomatosis only to a definite level, which is attained by the injection of cercariae into the portal vein in dozes lower than those used for subcutaneous infection.

On the basis of the author's and literary data the analysis of morphological and biological characters of nematodes of the genus Heterotylenchus was conducted. As a result the genus includes now only two species, H. aberrans and H. simplex (parasites of Diptera). For three species, H. bovieni, H. stammeri and H. wuelkeri (parasites of beetles), the genus Wachekitylenchus has been erected. The genus Wachekitylenchus is similar to Heterotylenchus, Paregletylenchus and Psyllotylenchus in its life cycle but differs from them in fabiform body of gamogenetic females, presence of cephalic lips and structure of the stylet in individuals of gamo- and parthenogenetic generations, and by the presence of lumen of the gut in free-living females and males. The genus differs from Heterotylenchus and Paregletylenchus in the structure of the genital system of females of both generations, viviparity and the presence of gubernaculum in males.

The amino acid composition of protein in the oocysts of Eimeria tenella has been studied in detail by using the new method of purification of the coccidial oocysts. 35 amino acids and their metabolites have been established for the first time at the exogenous stages of development of E. tenella. The oocyst sporulation is noted to be followed by quantitative changes of the majority of free amino acids and their metabolites.

Only mature ticks, engorged females and hungry imago hibernate in mountain regions of Armenia. According to the author's observations eggs of ticks as well as their larvae are not capable of hibernating. In females of spring satiation the development of eggs proceeds in most short periods from May to October. The longest period before the beginning of egg laying is observed in ticks of summer and autumn satiation. It becomes prelonged, in general, on account of hibernation of satiated females. Females of August — September satiation hibernate more successfully than females satiated in June and July.

Dermacentor raskemensis and Haemaphysalis pospelovashtromae were first recorded from the West Pamirs in the flood-land of the Gunt river at the height of 2700 m above the sea level. The ticks were collected from sheep, on which in addition to the above species D. marginatus was found. In the Rushansk region of the Mountain-Badakhshan district at the height of 2100 to 2300 m Rhipicephalus pumilio, R. turanicus and Hyalomma plumbeum were collected from domestic sheep and goats.

A new subspecies of simuliids, Chelocnetha angustitarsis zaporojae Pavlichenko ssp. n., from the steppe zone of the Ukraine is described. The subspecies is characterized by a peculiar structure of genital appendages of imago and a smaller number of rays in a big flabellum of larval mandibles.

The developmental cycle of the cestode Wardium stellorae (Deblock, Biguet et Capron, 1960) parasitic in marine Larus genei Brême from bitter-salt lake Tengiz (65—80‰) in Central Kazakhstan was studied. Artemia salina inhabiting in mass this water body in the intermediate host of this cestode. Morphological description and original figures of cysticercoids and mature cestodes are given.

In one summer old fishes of the pike perch, caught in the Kurish Gulf of the Baltic Sea in August — September of 1984, at 100% infection with A. paradoxus 94% of monogeneans were localized under the lower anterior angle of the operculum on the lateral surface of the intergill space (isthmus). In fishes 1+ on the isthmus there were found 52%, in pike perches 2+ 42%, and in fishes 3+ 67% of worms. In older fishes (4—10+) the number of worms on the isthmus accounts for 5% of their total number while others are localized on gill filaments. Variability of sizes, chitinoid structures and microlocalization of worms depending on the age of fish were established.

Summary is absent.

A brief analysis of the state of knowledge of Protozoa occurring in reptiles of the Soviet Union is given. The importance of research on protistofauna of reptiles is substantiated and the main directions for the elaboration of this question are indicated.

Summary is absent.