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Fibrinogen-related proteins (FREP) are calcium-dependent lectins with one fibrinogen domain and one or two immunoglobulin-like domains. FREP of gastropod molluscs have an ability to somatic diversification, which is unique among pathogen-recognizing molecules of invertebrates. The structure of the genomic regions encoding FREP implies the possibility of alternative splicing and somatic mutagenesis. Since the discovery of FREPs in Biomphalaria glabrata, these molecules have been described in many gastropods. At least 14 subfamilies of FREPs are currently known. FREPs of different subfamilies selectively participate in the immune response to various pathogens. In particular, their role in defense reactions to trematode invasion and in resistance to trematodes of particular species has been confirmed. The supposed functions of FREP are diverse, ranging from recognition of foreign matter to opsonization and neutralization of pathogens. Despite the abundance of FREPs studies, the Russian literature on this subject is scarce. The main purpose of this review is to analyze the available information on gastropod FREPs and to discuss their role among pathogen-recognizing receptors of molluscs.

The fauna of endobiotic ciliates of the rumen of the Siberian roe deer Capreolus pygargus from Terneisky region of Primorsky Territory of Russia was investigated. In the investigated roe deer, a single ciliate species, Entodinium dubardi, was found, and it was found in less than 40% of hosts in the surveyed population. We assume that the extremely low species diversity of endobiotic ciliates and the low degree of infestation of hosts are primarily associated with a decrease in the level of herding, as well as with the peculiarities of the diet of roe deer.

Taxonomic diversity and peculiarities of distribution and host-parasite relations of fleas of the Palearctic genus Frontopsylla (Leptopsyllidae, Paradoxopsyllinae) are analyzed in the present review. The role of separate representatives of this genus as pathogen vectors and reservoirs in natural plague foci of Eurasia is observed. It is demonstrated that 11 out of 36 flea species of the genus Frontopsylla are marked as main, secondary, or occasional vectors of this infection.

The results of long-term (2005-2020) monitoring of combined tick-borne encephalitis (TBE) and tick-borne borrelioses (TBB) natural foci in several sites of southern part of Baikal region are presented. The studied territory showed high degree of heterogeneity of adult Ixodes persulcatus population density and their infection with TBEV and borrelians. Significant difference between the studied sites regarding pathogenicity of vectors with positive TBEV - ELISA results for laboratory mice has been revealed. Positive correlation between vector abundance and TBEV antigen prevalence and the number of murine viral isolates has been shown. The incidence of TBE on the studied territory also correlated with ELISA results and success of isolation on worm-blooded animals. The number of Borrelia PCR positive results was higher if the ticks abundance was high, but TBB incidence correlated neither with ticks abundance, no with their Borrelia infection rates.

Some biological traits of Tomicobia seitneri (Ruschka, 1924), parasitoid of the spruce bark beetle Ips typographus L., 1758, were studied. Fraction of parasitized bark beetles is usually higher in the second half of summer. Tomicobia seitneri possesses two generations per year, and its complete development in the natural conditions of Moscow Province lasts for 32-37 days while under laboratory conditions at 24°С it takes 30-68 days to develop from an egg to adult. The analysis of pheromone traps demonstrated that the infested spruce bark beetle I. typographus is able to fly for at least about 20 days after being parasitized by T. seitneri. Life expectancy of the infested beetles and fertility of females T. seitneri under laboratory and natural conditions differ and most likely depend on their nutritional conditions. After end-of-the-winter emergence from the bark, T. seitneri females have no mature eggs. After additional feeding for 3-4 days, females contain 3 eggs on average. The average number of eggs in females collected at the beginning of I. typographus flight is 3 (3.34 ± 3.61, n = 32). In mid-summer, females with a large number of eggs are predominant whereas females without eggs are rare (average 20.16 ± 6.81 eggs, minimum - 1 egg, maximum - 38 eggs, n = 114). To rear T. seitneri under laboratory conditions successfully, it is necessary to create favorable conditions for the development of their bark beetle host. The article contains information about the detected forms of larvae of T. seitneri.

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