Biomedical subjects

K V Galaktionov

Publications and source records attributed to K V Galaktionov.

18 recordsLinked to original sources

PubMed2006

Infection patterns in white sea blue mussels Mytilus edulis of different age and size with metacercariae of Himasthla elongata (Echinostomatidae) and Cercaria parvicaudata (Renicolidae).

Infection of mussels Mytilus edulis L. by 2 trematode species was studied in a natural intertidal population in the Chupa inlet of the White Sea. The prevalence of metacercariae of Himasthla elongata (Mehlis, 1831) and Cercaria parvicaudata (Stunkard & Shaw, 1931) in mussels reached 100% in 3 to 4 yr old molluscs and remained at this level in older individuals. Infection intensity increased evenly with the age of the molluscan host, showing a tendency to decrease only in the oldest (9 yr old) mussels. These patterns of age dynamics of prevalence and infection intensity were associated with accumulation of trematode larvae in the course of the molluscs' lives. Ability of metacercariae to exist in mussels for long periods (at least 2.5 yr) was verified in the course of an experiment, during which infected molluscs were kept in a subtidal net cage. Decrease of infection intensity in the oldest individuals may reflect selective mortality of the most severely infected molluscs. Among mussels of the same age, higher infection intensity values occurred in larger individuals. This may be due to an enhanced pumping rate in large molluscs, which increases the probability of cercariae, free-living trematode larvae, infecting them via water currents.

Analysis of Variance↗

PubMed2006

One of the most complex life-cycles among trematodes: a description of Parvatrema margaritense (Ching, 1982) n. comb. (Gymnophallidae) possessing parthenogenetic metacercariae.

This study used light and electron microscopy to provide observations and morphometric details of the life-cycle of the gymnophallids (Trematoda, Digenea), Parvatrema margaritense (Ching, 1982) n. comb., the parthenogenetic metacercariae ('germinal sacs') of which were previously described by Ching (1982) as Cercaria margaritensis. The research was instigated by the discovery, on the Barents Sea coast, of a high prevalence of gymnophallid sporocysts and cercariae in the bivalve Turtonia minuta and an equivalent presence of distinctive gymnophallid metacercariae in the gastropod Margarites helicinus. Experiments and data obtained from naturally infected M. helicinus demonstrated that cercariae released from the bivalves invaded the gastropods to give rise to the metacercariae. Two generations (M1 and M2) of these parthenogenetic metacercariae were formed in the extrapallial cavities of their bivalve hosts and they, in turn, gave rise to a third generation (M3) which was shown to infect marine ducks such as the eider (Somateria mollissima). As only small numbers of cercariae are released from T. minuta, it was concluded that the inclusion of parthenogenetic metacercariae in the life-cycle is particularly significant. It allows each cercaria that infects M. helicinus to give rise to over 2000 invasive metacercariae. Evidence suggests that the parthenogenetic metacercariae are commensal rather that parasitic in the pallial cavities of their hosts. Implications of this for theories of early digenean evolution are discussed.

Animals↗

PubMed2004

An ultrastructural study of excretory system development in the cercariae of Prosorhynchoides gracilescens (Rudolphi, 1819) and Prosorhynchus squamatus Odhner, 1905 (Digenea, Bucephalidae).

The ultrastructure of the developing excretory system of Prosorhynchoides gracilescens and Prosorhynchus squamatus cercariae is described. The development pattern was similar in both species. In early embryos the two main collecting tubes were composed of a layer of cells which were wrapped around the lumen. Later, the tubes fused and the excretory epithelium of the fusion zone and that of the lateral caudal ducts became a syncytium. The collecting tubes in the cercarial body retained their cellular organization. As the tails grew, additional excretory pores were formed in the tail stem where thickened portions of the caudal duct epithelium contacted the surface tegument. Following this, the distal portions of the lateral caudal ducts lost contact with the primary excretory pores and progressively degenerated. Excretory atrium development started with differentiation of secretory active cytons peripheral to the fusion zone. These cells gave rise to cytoplasmic extensions that penetrated the fusion zone wall to eventually form a continuous cytoplasmic layer. This layer eventually replaced some of the fusion zone excretory epithelium and became the lining of the excretory atrium. The anterior end of the fusion zone differentiated into an excretory bladder and a short posterior portion gave rise to the caudal vesicle.

Animals↗

PubMed2004

An ultrastructural study of the cercarial excretory system in Bucephaloides gracilescens and Prosorhynchus squamatus.

The ultrastructure of the flame cells, capillaries, collecting tubes, excretory bladder, excretory atrium, caudal vesicle, lateral caudal ducts and excretory pores of cercariae of Bucephaloides gracilescens (Rudolphi, 1819) Hopkins, 1954 and Prosorhynchus squamatus Odhner, 1905 (Digenea: Bucephalidae) is described. Both species are essentially similar except for some details. The terminal parts of the protonephridia have all the structural features that are typical of trematodes. The collecting tubes in the cercarial body are composed of cells that are wrapped around the lumen. The main collecting tubes are joined to the excretory bladder syncytium by septate junctions. Features of P. squamatus excretory bladder epithelium indicate that it is involved in secretory activity, but this is not the case in B. gracilescens. In both species the luminal surface of the excretory bladder epithelium is increased by lamellae, and the basal plasma membrane forms invaginations. In the bladder syncytium of P. squamatus both apical lamellae and basal invaginations are more developed and mitochondria are also more numerous. The excretory atrium is lined by a syncytium with nucleated cytons located in the surrounding parenchyma. The atrium lining is not continuous with the body tegument and possesses specific secretory inclusions and a thick glycocalyx. Septate junctions connect the atrium syncytium to the excretory bladder epithelium at its anterior end and to the syncytial excretory epithelium lining the caudal vesicle and the lateral caudal ducts at its posterior. In the excretory pores the caudal duct syncytium is joined to the tegument by septate desmosomes.

Animals↗

PubMed2004

Evolutionary relationships within 'pygmaeus' group microphallids using genetic analysis and scanning electron microscopy.

There are four species of 'pygmaeus' microphallids, namely Microphallus pygmaeus, M. piriformes, M. pseudopygmaeus and M. triangulatus (Trematoda: Microphallidae) which are parasites of marine birds and their sporocysts give rise to transmissible metacercariae inside littoral gastropods (mostly littorines). Universally primed polymerase chain reaction (UP-PCR) showed no apparent pattern between genetic diversity of the metacercariae as estimated by genomic banding profiles and their geographic region or molluscan host species. At the same time UP-PCR product cross-hybridization showed that M. pseudopygmaeus and M. triangulatus are genetically very similar, indicating that these taxa represent one species complex. In contrast, M. pygmaeus and M. piriformes are genetically well separated from each other and also from the pseudopygmaeus-triangulatus complex. Scanning electron microscopy of ventral spines, and analyses of spine angles and the number of teeth per spine, showed that all species differed significantly from one another. It was concluded that M. piriformes represents the original western member of the 'pygmaeus' group. Microphallus pygmaeus probably diverged from M. piriformes as it progressively specialized for sea duck final hosts. Microphallus pseudopygmaeus and M. triangulatus diverged from each other and the piriformes-pygmaeus ancestral line relatively recently. Microphallus pseudopygmaeus specialized for adoption of a wide range of gastropod host species and M. triangulatus developed morpho-functional specialization associated with final host exploitation.

Animals↗

PubMed2003

An ultrastructural study of reproduction in the parthenogenetic metacercariae of Cercaria margaritensis Ching, 1982 (Digenea: Gymnophallidae).

The parthenogenetic metacercarial stages of the gymnophallid trematode Cercaria margaritensis are found in the extrapallial cavity of the subtidal prosobranch mollusc Margarites helicinus. The primary metacercariae (M1) produce second-generation metacercariae (M2) which become independent and give rise to M3 metacercariae which are infective to the definitive host, the common eider (Somateria mollissima). This study used transmission electron microscopy to follow the development of M2 inside M1 organisms and M3 inside M2 organisms. The process is similar in both cases with embryos developing from individual cells from the parent body walls. In each case the brood sac was divided into brood chambers by multilaminated cells and both M2 and M3 embryos developed inside embryonic membranes that originated from specialized blastomeres. The tegument of M2 and M3 embryos developed in a similar manner underneath the embryonic membrane. Both the multilaminated cells and the embryonic membranes possessed features that indicated that they are involved in transport of nutrients. It is suggested that the continuous nature of M2 and M3 embryo development may well be similar to that postulated for ancestral digeneans.

Animals↗

PubMed2000

Digeneans from intertidal molluscs of SW Iceland.

The fauna of digenean daughter-sporocysts, rediae, cercariae and metacercariae infecting molluscs Littorina spp., Onoba aculeus. Nucella lapillus and Epheria vincta has been studied in the Skerjafjordur and Grindavik regions of SW Iceland. In total, intramolluscan stages of 19 digenean species were recorded; 14 of them are new for Iceland and one of them, a microphallid named Cercaria islandica I, was unknown. A description of this new microphallid cercaria is provided. In addition, the identification and separation of the intramolluscan stages of some microphallid, renicolid and echinostomatid species are discussed. Consideration is given to difficulties encountered when identifying digenean species found on the coasts of European countries. Problems have arisen largely because larval and adult stages have been described and named independently and in isolation, synonyms are common and many "definitive" descriptions are inadequate or incomplete.

Animals↗

PubMed1999

Distribution patterns of marine bird digenean larvae in periwinkles along the southern coast of the Barents Sea.

An important component of the parasite fauna of seabirds in arctic regions are the flukes (Digena). Different species of digeneans have life cycles which may consist of 1 intermediate host and no free-living larval stages, 2 intermediate hosts and 1 free-living stage, or 2 intermediate hosts and 2 free-living larval stages. This study examined the distribution of such parasites in the intertidal zones of the southern coast of the Barents Sea (northwestern Russia and northern Norway) by investigating 2 species of periwinkles (Littorina saxatilis and L. obtusata) which are intermediate hosts of many species of digeneans. A total of 26,020 snails from 134 sampling stations were collected. The study area was divided into 5 regions, and the number of species, frequency of occurrence and prevalence of different digenean species and groups of species (depending on life cycle complexity) were compared among these regions, statistically controlling for environmental exposure. We found 14 species of digeneans, of which 13 have marine birds as final hosts. The number of species per sampling station increased westwards, and was higher on the Norwegian coast than on the Russian coast. The frequency of occurrence of digeneans with more than 1 intermediate host increased westwards, making up a larger proportion of the digeneans among infected snails. This was significant in L. saxatilis. The prevalence of different species showed the same pattern, and significantly more snails of both species were infected with digeneans with complicated life cycles in the western regions. In L. saxatilis, environmental exposure had a statistically significant effect on the distribution of the most common digenean species. This was less obvious in L. obtusata. The causes of changing species composition between regions are probably (1) the harsh climate in the eastern part of the study area reducing the probability of successful transmission of digeneans with complicated life cycles, and (2) the distribution of different final hosts.

Animals↗

PubMed1997

The structure and formation of metacercarial cysts in the trematode family Microphallidae travassos 1920.

This study deals with the formation of the metacercarial cysts of four microphallid trematodes, Maritrema subdolum, M. arenaria, Levinseniella brachysoma and Microphallus claviformis. The first observable cyst was present around Maritrema arenaria 18 h p.i. (post-infection). The other species had not developed a cyst by day 8 p.i. but their cysts were apparent by day 16 p.i. These were bi-layered and that of M. subdolum was thicker than those of L. brachysoma and Microphallus claviformis of the same age. The structure of older cysts varied substantially between the four species. Microphallus claviformis and Maritrema subdolum cysts were fully formed at 30 days p.i. Like those of M. arenaria they were bi-layered, the outer layer (up to 3 microm thick) being electron-dense and the inner one (up to 7 microm thick) being less electron-dense. The cysts of fully formed L. brachysoma metacercariae were much more complex, composed of four layers, one of which was divisible into three sub-layers. It was concluded that the outer cyst layer was the product of secretory granules which were previously identified in cercarial tegument. The inner, thicker layer was derived from several sources. These included small tegument vesicles produced over the entire surface of the metacercariae, larger fragments of tegument released from the anterio-ventral region and material liberated from the metacercarial excretory bladder. This heterogeneous material accumulated in the cyst lumen for some time before becoming polymerized to form the thick inner layer or layers of the metacercarial cysts.

Animals↗

PubMed1994

The glands of trematode cercariae of the family Microphallidae Travassos, 1920.

The ultrastructure of the glands of microphallid cercariae is described. The fully-formed cercariae possess only penetration glands opening onto the surface of the tegument. Cercarial embryos have tegumental glands transferring their secretion in the tegument. In all studied species two anterior pairs of penetration glands produce identical granules while two posterior pairs produce heterogeneous granules of various shapes and sizes. Tegument cells are divided into mucoid and two other types of tegument glands (TG1 and TG2). The mucoid glands of Microphallinae cercariae produce large fibrous granules, while those of Maritrematinae cercariae produce osmiophil ones. TG1 cells of Maritrema subdolum produce large rod-shaped granules and TG1 cells of Levinseniella brachysoma, Microphallus sp. and M. claviformis produce two types of osmiophil granules. TG2 produce small rod-shaped granules. The association of gland ultrastructure with their function and features of the microphallid life-history are discussed.

Animals↗

PubMedDate not supplied

[The organizational characteristics of the generative material and the the proliferative dynamics of trematode mother sporocysts].

Analysis of miracidia germinal material organization and proliferation dynamics of mother sporocysts enabled us to divide them into three well-defined groups. The first one includes species whose miracidia possess only differentiated (mature) generative cells and embryos of earlier stages of cleavage. In this case during parasite phase of development of maternal sporocysts the generative function is not performed. To the first group therefore trematode species with pedogenetic larvae could be attributed also. The next group embraces species whose miracidia as well as mature generated cells have some undifferentiated cells; thus the parasitic phase of mother sporocyst development acquires restricted proliferative capacity. The third group consists of species with higher trematodes dominating. They perform generative function exclusively at parasitic phase of mother sporocyst development. Representatives of more archaic and ancient species are the bases of the first two groups on the contrary. Such type of distribution can not occur occasionally and apparently reflects first steps of emergenes of parthenogenetic generations of trematodes.

Animals↗

PubMedDate not supplied

[The finding of a cestode in the little auk Alle alle on Franz Josef Land].

One of 14 dovekeys (Alle alle) investigated in August 1993 on Hooker Island (Franz Joseph Land) was found to harbour a single specimen of an early immature dilepidid cestode attributed as Alcataenia sp. The rostellum bears a double crown of 22 hooks, 0.025-0.027 mm in length. Except Threlfall (1971) there was no information concerning dovekey's parasites.

Animals↗

PubMedDate not supplied

[Effect of parasites on host adaptation to abiotic environmental factors: host-parasite relationship of trematode parthenites--mollusc system].

This laboratory study examined the survival of extreme environmental conditions by the White Sea periwinkle Littorina saxatilis. Molluscs from localities with high and low prevalence of Microphallus piriformes, which is a representative of the "pygmaeus" group of digeneans (Microphallidae), were compared. These parasites have not a stage of free-living cercariae in their life cycle. Metacercariae mature inside the sporocysts parasitizing the molluscan host. No negative influence of infection was found on resistance of molluscs to prolonged desiccation and extremes of air and water temperature. On the contrary, significant lower mortality of high infected snails was observed in some experiments. Exposure to fresh water was the only treatment that caused more intensive mortality of high infected snails in comparison with low infected one. The results of the experiments were discussed taking into consideration the available data on mechanisms of molluscan resistance and features in the relationships of "pygmaeus" group sporocysts with the organism of molluscan host. It was emphasized that the wide spread opinion regarding the only negative influence of trematode infection on the resistance of infected molluscs should be revised.

Adaptation, Biological↗

PubMedDate not supplied

[Respiration and motor activity of cercariae of three trematode species from the intertidal mollusc Littorina littorea L (Gastropoda) from the White sea].

The age dynamics in oxygen consumption of the cercariae Himasthla elongata, Cryptocotyle lingua and Cercaria parvicaudata (Renicola sp.) was studied using modified Winkler's method. It was detected that under stable temperature and water salinity conditions the rate of oxygen uptake depends directly on cercariae size. The highest intensity of energetic metabolism was recorded in the first few hours of cercariae life when their movement activity was maximal. The following reduction of oxygen consumption passed unequally in three cercariae species studied. Large, long-lived H. elongata cercariae after relatively short period of active swimming turn to crawling on the bottom. The rate of oxygen uptake in such cercariae was two times less than in free-swimming ones and remained approximately invariable up to the cercariae death. The smaller sized, short-lived Renicola sp. cercariae swim actively in the water and during this time the level of their energetic metabolism remains more or less stable. It decreased drastically after cercariae sinking to the bottom, after that they perished very soon. Also relatively small C. lingua cercariae alternate the active and passive phases of swimming. Thanks to that they consume the energetic resources economically and prolong their longevity. During free-swimming period the rate of oxygen uptake of C. lingua cercariae remains more or less stable. As in the case of Renicola sp. cercariae, it decreased drastically after the cercariae sinking to the bottom. Apparently such cercariae lose their ability to infect the second intermediate host (fish).

Animals↗

PubMedDate not supplied

[Comparison of resistance to environmental factors of the molluscs Hydrobia ulvae infected with trematoda parthenitae and free from infection].

The influence of trematode infection, mainly with Microphallus claviformis, onto the resistance of mudsnails Hydrobia ulvae to fresh water, desiccation and extremely high temperature has been investigated. It was found out in all variants of experiments that the intensity of mortality in infected individuals is reliably higher than in individuals free of infection. It is suggested, that the negative influence of parasites on the resistance of hosts is related to the disturbance of molluscs' capability to isolate themselves from extremal condition by shutting up the shell with operculum. It is proved by the high rate of salt loss in the infected molluscs in a comparison to non-infected individuals. Our hypothesis based on results obtained and reference data suggests that the rate of trematode parthenites' influence onto the resistance of molluscs depends upon the character of interrelationships in hostparasite systems. Normally, the trematode species having the active cercaria stage in the life cycle show more negative impact onto the resistance of infected molluscs, than those species, larval stages of which develop to metacercaria inside the parthenites.

Animals↗

PubMedDate not supplied

[A comparative analysis of the helminth fauna of kittiwake Rissa tridactyla (Linnaeus, 1758) and glaucous gull Larus hyperboreus Gunnerus, 1767 from different parts of the Barents Sea].

The article is based on the results of helminthological observations made on kittiwake Rissa tridactyla and glaucous gull Larus hyperboreus in 1991-2001 in different areas of the Barents Sea (Eastern Murman coast, Franz Josef Land, Novaya Zemlya, Spitzbergen). 18 helminth species (2 trematodes, 11 cestodes, 4 nematodes, and 2 acanthocephalans) were recorded in the kittiwakes and 19 (3 trematodes, 9 cestodes, 5 nematodes and 2 acanthocephalans) species were recorded in the glaucous gulls. Trematodes were absent in the birds collected at the Franz Josef Land and the northern island of Novaya Zemlya. 3 trematode species, namely Gymnophallus sp. (somateria?), Microphallus sp. 1 (M. pseudopygmaeus), and Cryptocotyle lingua were found in the glaucous gulls of western Spitzbergen. It was supposed that the life cycles of these parasites can be completed there. On the other hand, coastal ecosystems of Arctic archipelagoes turn out to be favourable for the transmission of some cestodes. This is closely connected with the regional traits in the marine bird diet, namely the increase of the amphipod (intermediate hosts of hymenolepidids and some dilepidids) and polar cod (supposed second intermediate host for some tetrabothriids) portion in Arctic. As a result, cestodes are the base of the helminth fauna of kittiwakes and glaucous gulls of the Barents Sea, by their species richness, prevalence and abundance. Nematodes and acanthocephalans were represented by a few species with low infection intensity. The main ecological factors affected the regional difference in the species richness and abundance of the helminths parasitising kittiwakes and glaucous gulls in the Barents Sea are proposed. Those are regional climatic features and regional traits in the behaviour and food priorities of birds, and also the distribution of the helminths intermediate hosts, invertebrates and fishes. The phenomenon of host specificity lowering with respect to the definitive host was recorded in some cestode species (Microsomacanthus diorchis, M. microsoma, and Arctotaenia tetrabothrioides) on the border of their distribution ranges, the coastal ecosystems of Arctic.

Acanthocephala↗

PubMedDate not supplied

[The structure of the cercarian tegument of microphallid trematodes].

The tegument of mature cercariae of Microphallus sp. Podlipajev, 1979, M. claviformis, Levinseniella brachysoma and Maritrema subdolum consists of the outer syncytial layer filled with several types of secretory inclusions. Cytons and subtegumental cell ducts are absent. Covers of Microphallus cercariae have structure typical of larvae of trematodes. The tegument surface of L. brachysoma cercariae carries lamelli, spines are divided into two parts: short massive body sharpened at fore end and long thin stalk connected with basal membrane. The tegument surface of M. subdolum larvae forms tongue-like protrusions, modified spines serve as their frame. The development of tegument of the above species during cercaria morphogenesis has been traced. It is shown that at first in embryos syncytial lamina of the tegument is formed. Within it rudiments of spines have been detected as narrow transversal columns of mediate electron density. Henceforward syncytial layer has thickened, provisional spines have become conical, their matrix has become fibrous. Then the joining of protrusions of subtegumental glandular cells to outer syncytium has begun. These cells have been arranged into three types depending on the character of secret produced. The spines have acquired the species-specific structure. In members of the genus Microphallus they have become massive, and both in L. brachysoma and M. subdolum they have lengthened and subdivided into body and stalk. Spines of M. subdolum have flattened appreciably, their bodies have been found within tegumental tongue-like protrusions.

Animals↗

PubMedDate not supplied

[Variations in the number of metacercariae in the daughter sporocysts of Microphallus pygmaeus (Trematoda: Microphallidae)].

The daughter sporocystes of Microphallus pygmaeus from the snails of Littorina saxatilis and L. obtusata were investigated. The average quantity of metacercariae in sporocysts is influenced by host species, its syze and by the season. There are differences in the average number of larvae from parthenites of L. saxatilis, collected in the Barents and White seas.

Animals↗