Research interests: Trematodes morphology and evolution of their life cycles. Adaptations of trematodes to transmission in different ecosystems. Relationships between trematodes and their hosts – mollusks at the organismal and populational levels. Taxonomy and phylogeography of trematodes. Fauna and life cycles of parasites of marine animals. Circulation patterns of marine birds parasites in Arctic and subArctic coastal ecosystems. Marine parasitology. Problems of general parasitology.
Prize named after E.N. Pavlovsky (RAS, 2005) for two monographs on biology and evolution of trematodes (with A.A. Dobrovolsky)
St. Petersburg State University, dep. Invertebrate Zoology, a course "General Parasitology" Masters course. Scientific supervision of undergraduate and graduate students (1-3 students per year, currently D.Losev and A.Gonchar). Student projects are mainly related to the work on the White Sea Biological Station and are within the scope of the main directions of research named below.
Studies were conducted since 1999 in the intertidal zone of the Chupa Inlet of the Kandalaksha Bay of the White Sea. We analyze component populations of 20 species of trematodes, using as first intermediate hosts of intertidal molluscs Littorina saxatilis, L. obtusata, L. littorea, Hydrobia ulvae and H. ventrosa: Himasthla elongata, H. continua, Cryptocotyle concavum, C. lingua, Levinseniella brachysoma, Maritrema subdolum, Microphallus similis, M. claviformis, M. pirum (= M. somateria), M. pygmaeus, M. piriformes, M. triangulatus, M. pseudopygmaeus, Cercaria parvicaudata (= Renicola sp.), Paramonostomum anatis, P. alveatum, P.chabaudi, Cercaria Notocotylidae sp. 12 Deblock, 1980, Cercaria Notocotylidae sp. 13 Deblock, 1980, Bunocotyle progenetica. We study the dynamics of the demographic composition of groups of sporocysts and rediae and the seasonal production of cercariae. We found that production of cercariae by parthenites (sporocysts and rediae) stops in the cold period and resumes only when the water temperature rises in spring. These processes are accompanied by rearrangements in the demographic groups of the parthenites, which differ between the species that form the local component populations (= infrapopulations) and self-reproducing infrapopulations. Among the studied species of trematodes found cold- and warm-loving forms, in which the release of cercariae block at lower and higher water temperatures, respectively. Particular attention is paid to forecasting of possible changes in the transmission of trematodes in coastal ecosystems due to global climatic changes. Work performed in collaboration with K.E. Nikolaev, I.A. Levakin and V.V. Prokofiev, with the participation of students of St. Petersburg State University.
2. Biology and behavior of free-living larvae (cercariae) of trematodes circulating in the coastal ecosystems of the northern seas.
We study the nature of the motor activity of cercariae, especially their respiration at different periods of life, the age dynamics of the invasive ability, the daily and long-term rhythm of emission of cercariae from the host mollusk at different temperatures. It has been established that temperature is the leading factor determining the dynamics of the output of cercariae of the host mollusk for most of the intertidal trematodes . Long-term emission of cercariae from an infected clam is subject to recurring natural oscillations, the frequency of which is species-specific. The project is carried out in collaboration with V.V. Prokofiev (Pskov State Pedagogical University - PGPU), involving students of PGPU and St. Petersburg State University.
Currently, the work focuses on studying the characteristics of infection of second intermediate hosts by trematode cercariae. Experimental studies are performed on the model system consisting of mussel Mytilus edulis and cercariae Himasthla elongata and Cercaria parvicaudata (= Renicola sp.). We study intrapopulation variability of the mussel resistance to parasites and the cellular and humoral mechanisms that underlie the mechanism of resistance to the cercariae infection in the mussel lines resistant to infection by cercaria. Ecological and population component of work includes development and testing of quantitative approaches to assessing the success of transmission of trematodes in coastal ecosystems of the White Sea. These include assessing the loss of free-floating larvae (cercariae) on the way between the first and the second intermediate host and defining the role of different host species in the transmission of trematodes. This project is performed by the researchers from the Zoological Institute RAS I.A. Levakin and K.E. Nikolaev, students of St. Petersburg State University and the Polytechnic University in collaboration with a group of comparative immunology IEM RAMS (Head A.V. Polevschikov).
Recent studies are focused primarily on the trematodes, circulating in the coastal zone of the Barents, White, Norwegian and Okhotsk Seas and Iceland. We described new species of trematodes and clarified some of the taxonomic diagnoses. We also studied experimentally a new type of the trematode life cycle characteristic of some representatives of fam. Gymnophallidae (Galaktionov et al., 2006; Galaktionov, 2007). We use morphological and molecular markers to study phylogeography of trematode taxa. Work is done in collaboration with the Laboratory of Parasitology, Institute for Biological Problems of the North (IBPN), FEB RAS (K.V. Regel, S. Orlovskaya, G.I. Atrashkevich), University of Iceland (K. Skirnisson), Ulster University (Northern Ireland, S.W.B. Irwin, D.H. Saville) and the Natural History Museum (London, P. Olson).
We study the distribution of parasites of seabirds in the arctic and subarctic regions of the Barents and Norwegian Seas and the White Sea. We investigate the formation of foci of marine bird infection with parasites and the bird adaptations, preventing the invasion by pathogenic worms. At present, special attention is paid to areas lying on the major flyways of migratory birds and the sites crucial to their feeding (south-east of the Barents Sea - the so-called Pechora Sea). The analysis of trophic relations of common eiders (Somateria mollissima) in different geographic areas (from Ireland and Iceland in the west to the Okhotsk Sea in the east) and the patterns of helminth invasions associated with regional characteristics of bird feeding. We also study the ways of transmission of the major species of parasites of common eiders in the seas of the Palearctic. The work is carried out in collaboration with the staff of the Murmansk Marine Biological Institute KSC RAS (V.V. Kuklin, V. Krasnov), Institute of Biological Problems of the North (IBPN), FEB RAS (K.V. Regel, S. Orlovskaya, G.I. Atrashkevich ), University of Iceland (K. Skirnisson), Ulster University (D.H. Saville), University of Dublin (Trinity College, J.G. Wilson, C. Holland) and the Norwegian Institute of Natural Research (NINA) (J.O. Bustnes).
The work is theoretical in nature and is based both on literature data and on the results of the projects mentioned above. Many aspects are summarized in the monographs (Galaktionov, Dobrovolsky, 1998; Galaktionov, Dobrovolskij, 2003). Currently the main focus of the study is the reconstruction of the phylogenetic relationships among the different taxa of trematodes based on the analysis of the of the life cycles, morphological and functional traits of parthenogenetic and hermaphroditic generations and critical analysis of the phylogenies obtained using molecular markers. During the study we developed the concept of ecological evolution of trematodes and different versions of the natural systems of the class Neodermata. The work is conducted in close and creative collaboration with A.A. Dobrovolsky. Morphological studies performed in together with the staff of the Zoological Institute RAS I.M. Podvyaznaya and S.W.B. Irwin, D.H. Saville (Ulster University, Northern Ireland, UK).
All of the above directions partially fit into the framework of the planned studies of the Zoological Institute RAS and at different times supported by RFBR, the program "Universities of Russia, INTAS, the Royal Society of Great Britain, the Norwegian Research Council, the Department of Environment of Norway, Iceland Research Foundation and the University of Iceland.