Trematode Parthenitae Research Articles

Effect of trematode infection on cardiac activity of marine gastropod Littorina littorea in situ and under laboratory conditions.

Physiological mechanisms underlying relationships between the trematode parthenitae and their molluscan hosts are poorly understood. In this study, we estimated the cardiac function of gastropods Littorina littorea L. infected with Himasthla elongata and Cryptocotyle lingua under laboratory conditions and in situ. The heart rate (HR) of the infected periwinkles was significantly lower than in the uninfected ones. HR of uninfected periwinkles in the natural environment followed a clear tidal pattern, with high values at high tide and low values at low tide. However, HR in most of the infected molluscs did not follow this rhythm. The decrease in HR was more pronounced in the periwinkles infected with C. lingua than with H. elongata. Thus, infection with C. lingua had a greater effect on the physiology and metabolic rate of periwinkles than infection with H. elongata.

Infection with Trematodes in Littorina obtusata Snails (Gastropoda: Littorinidae) with Different Shell Color Genotypes

The prevalence of infection with trematode parthenitae was studied in Littorina obtusata littoral periwinkles with different shell color genotypes. Activities of genes responsible for a purple or orange single-pigment background shell coloration was not found to affect the prevalence of trematode infection in periwinkles. In L. obtusata with a yellow-purple background shell color and a pattern of white pigment spots on the shell, the prevalence of infection with Microphallus piriformes and M. pygmaeus was lower than the theoretical expectation. The prevalence of infection in periwinkles with purple, orange, or white stripes on the shell did not differ from that of unstripped periwinkles. The differences found were presumably associated with genetically determined susceptibility to infection. Possible consequences of differential infection with trematodes in periwinkles with different shell color genotypes are discussed in terms of the stability of parasitic systems and possible changes in the phenotypic structure of the host population.

Bithyniid snails as hosts of Opisthorchiidae and Notocotylidae in the south of Western Siberia, Russia.

Opisthorchiasis and related infections are persistent and substantial public health burdens from eastern Europe to southeastern and northern Asia. Snails of the family Bithyniidae act as first intermediate hosts not only for the trematodes of the family Opisthorchiidae but also for those of the family Notocotylidae. There are certain morphological similarities between the aforementioned trematode cercariae. In order to find natural local foci of opisthorchiasis, which are established primarily according to the presence of infected bithyniid snails at the area under examination, it is crucial to correctly identify the rediae and cercariae of the trematodes. The aim of our investigation was to evaluate the role of bithyniid snails in the transmission of Opisthorchiidae and Notocotylidae in ecosystems in the south of Western Siberia. We have been studying the process of bithyniid snail dissemination in Western Siberia and examining their infection by trematodes from 1994 until now. A total of 16,213 bithyniid snails in 23 water bodies (in 28 localities) of four major basins situated in the Novosibirsk region were inspected for trematode infestation. Long-term research has been conducted in the Kargat river estuary and the Ob river floodplain for 15 and 25years, respectively. In both water bodies, the prevalence of notocotylid and opisthorchiid trematodes was positively correlated with the global land-ocean temperature index. Trematode parthenitae were identified if there were mature cercariae capable of leaving the shell of the host snail on their own. Identification to the species of opisthorchiid cercariae was verified using molecular genetic analysis methods targeting ITS2 locus. Opisthorchis felineus and Metorchis bilis, two opisthorchiid species that are potentially perilous to human health, were found in bithyniids in the Novosibirsk region. The mean prevalence of infection with notocotylid trematodes in bithyniid snails was higher than the corresponding prevalence of infection with opisthorchiid trematodes. The results of this study can be used to identify and predict natural foci of epidemiologically and/or epizootically dangerous diseases.

Transposons-Based Clonal Diversity in Trematode Involves Parts of CR1 (LINE) in Eu- and Heterochromatin.

Trematode parthenitae have long been believed to form clonal populations, but clonal diversity has been discovered in this asexual stage of the lifecycle. Clonal polymorphism in the model species Himasthla elongata has been previously described, but the source of this phenomenon remains unknown. In this work, we traced cercarial clonal diversity using a simplified amplified fragment length polymorphism (SAFLP) method and characterised the nature of fragments in diverse electrophoretic bands. The repetitive elements were identified in both the primary sequence of the H. elongata genome and in the transcriptome data. Long-interspersed nuclear elements (LINEs) and long terminal repeat retrotransposons (LTRs) were found to represent an overwhelming majority of the genome and the transposon transcripts. Most sequenced fragments from SAFLP pattern contained the reverse transcriptase (RT, ORF2) domains of LINEs, and only a few sequences belonged to ORFs of LTRs and ORF1 of LINEs. A fragment corresponding to a CR1-like (LINE) spacer region was discovered and named CR1-renegade (CR1-rng). In addition to RT-containing CR1 transcripts, we found short CR1-rng transcripts in the redia transcriptome and short contigs in the mobilome. Probes against CR1-RT and CR1-rng presented strikingly different pictures in FISH mapping, despite both being fragments of CR1. In silico data and Southern blotting indicated that CR1-rng is not tandemly organised. CR1 involvement in clonal diversity is discussed.

Trematode Parthenitae Infection Rate and Distribution of Kola Bay Actic Molluscs of the Genus Littorina

The study was carried out in 2018 in the littoral zone of Kola Bay during the autumn period in the areas of Abram Mys Settlement, Mishukovo Settlement and Retinskaya Bay. Molluscs of the genus Littorina were collected from various substrates: stones, algae, metal construction and soil. In addition, samples were taken not from a particular substrate, but along the borders of the littoral zone to study species composition of molluscs and common level of infection rate in study areas. Our data showed that L. saxatilis infested by mature trematode parthenitae prefer being on the surface of algae, metal structure, stones at low tide instead of hiding under the stones, in the thickness of algae and in other possible shelters. The study of age distribution among infested Littorina molluscs living on different substrates showed that the ratio of age groups is different and varies from 1+ to 13+. Distribution data are established and considered for infested molluscs by trematode parthenitae of the group ”pygmaeus”: Microphallus pygmaeus, M. piriformes, which are characterized by the absence of free-living cercariae. Trematode parthenitae of other species which have a stage of free-living cercaria in their life cycle are absent in molluscs during the autumn period.

Reproductive organs of trematode parthenitae during the cold season: an ultrastructural analysis using evidence from rediae of Bunocotyle progenetica (Markowski, 1936) (Digenea, Hemiuroidea)

Reproductive organs of trematode parthenitae during the cold season: an ultrastructural analysis using evidence from rediae of Bunocotyle progenetica (Markowski, 1936) (Digenea, Hemiuroidea)

The effect of trematode infection on the markers of oxidative stress in the offspring of the freshwater snail Lymnaea stagnalis.

Most invertebrate species exhibit immunological responses that can inactivate and eliminate penetrating parasites. Such immune responses in particular involve the formation of potentially toxic reactive oxygen species (ROS). We explored the immune capabilities of the first-generation (F1) offspring of naturally infected freshwater snails, Lymnaea stagnalis, in response to infection by trematode cercariae under laboratory conditions. The rates of ROS formation and peroxidase activity in the hemolymph of the F1 offspring of L. stagnalis parents infected by an asexual stage of trematodes were significantly higher than in F1 offspring of uninfected parents. Compared to offspring from uninfected parents, the growth rate of F1 snails from infected parents was higher, but survival was lower. After infection of F1 snails by trematode cercariae of Echinoparyphium aconiatum under laboratory conditions, the rate of ROS formation and peroxidase activity in the hemolymph of F1 offspring of uninfected parents increased compared to control snails. This pattern persisted throughout the entire 3-week observation period. In contrast, the rate of ROS formation in the hemolymph of F1 snails from infected parents after experimental infection by E. aconiatum cercariae did not differ from controls, and peroxidase activity even decreased. Thus, trematode parthenitae infection of parents could alter the immune response of their offspring.

Three Strigeid cercariae from Littorina littorea snail, Qarun Lake, Fayoum, Egypt.

Aim:The present study aims to focus on the role of common marine snails (Littorina littorea) as a vector for some trematode parasites.Materials and Methods:A total of 327 marine water L. littorea snails were collected during the summer of 2016 from a Qarun lake in the EL-Fayoum Governorate, Egypt. The snails were investigated for infection by trematode parthenitae through induction of cercarial shedding by exposure to light and crushing the snails. The species were stored in Search Laboratory of Zoology Department, Faculty of Science, Fayoum University.Results:Three species of Strigeid littorina cercaria were identified from the infected snails. They are described here and they identified in relation to close-up morphological features and linked to its snail hosts. They give the following names: Cercaria strigeid littorina type 1, C. strigeid littorina type 2, and C. strigeid littorina type 3. The incidence of infection by these cercariae was 33%, 25.7%, and 2.4%, respectively.Conclusion:This study is clarifying the importance of this marine snail as intermediate hosts for new trematode species.

The Role of Different Mollusk Species in Maintaining the Transmission of Polyhostal Trematode Species in Ukrainian Polissya Waters: The Specificity of Trematode Parthenogenetic Generations to Mollusk Hosts

Abstract The significance of different species of freshwater gastropods in transmission of polyxenic trematode species on the territory of Ukrainian Polissya is reviewed, with emphasis on instances of the specificity of trematode parthenogenetic generations to their mollusk hosts. For some hosts of polyhostal trematode parthenitae, the leading part in sustaining the local and regional populations of certain trematode species is confirmed. Groups of the common hosts also play an important role in circulation of these helminthes. In adverse conditions, populations of some trematode species can persist using the secondary and subsidiary hosts. Th e rare and accidental hosts of certain trematode species do not have a significant effect on their transmission.

Larval trematodes in bithyniid snails (Gastropoda: Bithyniidae) in the lake-rivers systems from the steppe zone (The West Siberian Plain, Russia)

Abstract A survey of cercariae and metacercariae (Trematoda, Digenea) from bithyniid snails (Gastropoda: Bithyniidae) in lake-river systems in Northern Kulunda (of the steppe zone of the West Siberia Plain) is presented. The role of Bithynia tentaculata (Linne, 1758) and Bithynia troscheli (Paasch, 1842) as the first intermediate hosts and as the second intermediate hosts of trematodes in the study area was accomplished for the first time. Twelve species of cercariae (8 families) and 12 species of metacercariae (6 families) were found in bithyniid snails. Altogether, bithyniid snails were infected with 23 trematode species including 16 genera in 11 families. New Cercariae Holostephanus sp. and five original species of trematode metacercariae, were discovered in bithyniid snails of the steppe zone of the West Siberia Plain. The dominant cercariae were those of the families Prosthogonimidae and Lecithodendriidae. The most prevalent metacercariae were Echinoparyphium aconiatum Dietz, 1909 and E. recurvatum Linstow, 1873 (both family Echinostomatidae) and Cyathocotyle bithyniae Sudarikov, 1974 (Cyathocotylidae). B. troscheli infected by trematode parthenitae of Holostephanus sp. was detected in the Russia for the first time.

Himasthla elongata: Implantation of rediae to the specific iteroparous long-living host, Littorina littorea, results in the immune rejection

All semelparous short-lived gastropods studied so far for the experimental transplantation of trematode parthenitae, from one specific host to another, showed more or less successful acceptance of implanted parasites. We implanted echinostomatid rediae, Himasthla elongata, to the specific iteroparous long-living host, coenogastropod Littorina littorea. Using simple and low-invasive implantation techniques we have tested 680 snails injected with 75 redia microhemipopulations (MHP) harvested from naturally infected snails. Neither young nor mature rediae were able to survive in the recipient periwinkles in the course of 30 days post-implantation. A strong immune response from the host was already evident within the first week after implantation: initial inactivation of motile rediae with toxic humoral immune factors, following encapsulation of the implants and increased hemocyte counts. In contrast, rediae from the same MHPs showed perfect survival rates in primary in vitro axenic cultures. The failure of the transplantation experiments is explained in terms of the compatibility matching phenotype model. In the studied host-parasite combination all periwinkles are potentially susceptible and all rediae MHPs are potentially infective, however the probability of the compatible phenotypes matching is virtually low. Low investment in L. littorea annual reproduction would result in increased investment in self maintenance and immune mechanisms, causing the general resistance to the trematode infestation. Presumably, this resistance is relatively higher in long-lived iteroparous gastropods compare to semelparous short-lived mollusks such as pulmonates.

Two 'new' renicolid trematodes (Trematoda: Digenea: Renicolidae) from the California horn snail, Cerithidea californica (Haldeman, 1840) (Gastropoda: Potamididae).

This manuscript describes the daughter parthenitae (sporocysts) and cercariae of two species of renicolid xiphidiocercaria that infect the California horn snail, Cerithidea californica, which serves as first intermediate host for a diverse and ecologically important guild of digenean trematode parasitic castrators. The two species described here have previously been considered to be a single morphospecies in ecological and evolutionary research. We provide provisional species names to respect that digenean alpha taxonomy is currently focused on sexual (adult) stages, while simultaneously respecting the spirit and utility of formal nomenclature in providing unambiguously unique, species-level names that also clarify to the extent possible species' taxonomic affiliations. The first species, Renicola sp. "polychaetophila" is most readily distinguishable from previously described renicolid xiphidiocercariae by a combination of (1) having a penetration gland duct arrangement of 2[(1+3+1)+1], (2) having one pair of penetration glands positioned anteriorly to the main gland cluster, (3) lacking tegmental spines, and (4) infecting Cerithidea californica. The second species, Renicola sp. "martini", is most readily distinguishable from other renicolid xiphidiocercariae that also have tegmental spines by a combination of (1) having a simple, bullet-shaped oral stylet sclerotized for 50-80% of its length, (2) having a cystogenous-gland field with an anterior-most extent about half way between the oral and ventral suckers, and (3) in infecting Cerithidea californica. Phylogenetic analyses using DNA (COI and ITS1) sequence data support that these two trematodes represent distinct species of Renicola. We also (1) provide an emended diagnosis for renicolid cercariae, (2) highlight a few morphological characters that may be useful for future taxonomic work involving renicolid xiphidiocercariae, and (3) suggest that future descriptive work involving trematode parthenitae include more information pertaining to the group of parthenitae as a whole.

TrematodeHimasthla elongata marinerelement (Hemar): Structure and applications

We cloned and analyzed Hemar1-the full-length mariner of Himasthla elongata. Hemar1 amount and distribution in the genome is typical for the transposable elements. Hemar1 closest relatives found in databases are the mariner-like element (MLE) of Girardia tigrina with 88% similarity in the most conserved transposase domain and Cemar1 of Caenorhabditis elegans with the most similar inverted terminal repeats. Hydra's (Cnidaria) MLE are the next in similarity to Hemar1. We checked whether sequences similar to Hemar1 exist in intermediate and definitive hosts of the parasitic trematode and did not find obvious similarity. This fact, together with the data of Hemar1 evolutionary position, argues against recent MLE-mediated horizontal transfer in this parasite-host model. Our results demonstrate that H. elongata generates genomic variability in asexual parthenogenetic generations within the snail. Transposon insertional display based on full-length sequence showed that Hemar1 could be located in the regions involved in generating clonal diversity in rediae and cercariae, that is, trematode parthenitae.

Loss of Trematode Parthenitae inPlanorbella trivolvis(Mollusca: Gastropoda)

Infection by trematode parthenitae (larval, asexual trematodes) has severe consequences for molluscan hosts, resulting in cessation of reproduction and early mortality. Here we present evidence that the freshwater snail Planorbella trivolvis can lose infections by trematode parthenitae. Of 8 P. trivolvis infected by reniferin parthenitae, 6 died within 2 wk, whereas the remaining 2 snails lost their infections within 82 days after initial examination. This phenomenon might suggest that molluscs can resist established trematode infections (i.e., "self-cure") or at least out-survive some trematode parthenitae.

Long-term variation in trematode (Trematoda, Digenea) component communities associated with intertidal gastropods is linked to abundance of final hosts

Trematodes are abundant parasites essential for maintaining stability of marine intertidal ecosystems. Despite the great ecological significance of trematodes, long-term dynamics of their communities remains practically unstudied. This study, based on 12-year-long seasonal monitoring of infection of Littorina and Hydrobia snails with 16 trematode species in the White Sea, aimed to reveal factors determining long-term variation in infection of intertidal snails by trematode parthenitae and larvae. Using the state-of-the-art method of singular spectrum analysis, we revealed trends in this variation and assessed their significance. Interestingly, these trends were not associated with oceanic and climatic parameters but were mostly determined by changes in abundance of the trematode final hosts. Moreover, the prevalence trends turned out to be connected with both large-scale events and local factors at the scale of the intertidal site. The main factors determining the long-term dynamics of the trematode component communities in the study area were the decreasing abundance of birds due to growing anthropogenic disturbance and the increasing abundance of the three-spined stickleback. The analysis of long-term trends of trematode prevalence in intertidal snails may be a sensitive indicator of the abundance dynamics of final hosts in the coastal areas of temperate and northern seas.

In vitro culture of marine trematodes from their snail first intermediate host

The ability to culture parasites outside their host (i.e. in vitro) is essential for several aspects of parasitological research. Here, a culture medium for marine trematode parthenitae was optimized using Philophthalmus sp. rediae from the intermediate snail host, Zeacumantus subcarinatus. The medium was optimized by sequentially testing the suitability of different levels of osmolality, different commercially available media, and different concentrations of supplemented chicken serum, while controlling for genetic variation among cultures. Philophthalmus sp. rediae survived up to 56days in cultures of the best tested medium, remaining active and continuously shedding cercariae. The broader suitability of the culture medium was tested using five other trematode species from different families (using either the same or other marine snails as first intermediate hosts): Galactosomum sp., Acanthoparyphium sp., Maritrema novaezealandensis, Curtuteria australis, and an undescribed species of the family Opecoelidae. Survivorship of rediae and sporocysts from these species ranged from eight days to 42days. The culture procedures developed here can therefore be used in the future as a system under which to culture marine trematode parthenitae for experimental studies.

Social organization in a flatworm: trematode parasites form soldier and reproductive castes

In some of the most complex animal societies, individuals exhibit a cooperative division of labour to form castes. The most pronounced types of caste formation involve reproductive and non-reproductive forms that are morphologically distinct. In colonies comprising separate or mobile individuals, this type of caste formation has been recognized only among the arthropods, sea anemones and mole-rats. Here, we document physical and behavioural caste formation in a flatworm. Trematode flatworm parasites undergo repeated clonal reproduction of 'parthenitae' within their molluscan hosts forming colonies. We present experimental and observational data demonstrating specialization among trematode parthenitae to form distinct soldier and reproductive castes. Soldiers do not reproduce, have relatively large mouthparts, and are much smaller and thinner than reproductives. Soldiers are also more active, and are disproportionally common in areas of the host where invasions occur. Further, only soldiers readily and consistently attack heterospecifics and conspecifics from other colonies. The division of labour described here for trematodes is strongly analogous to that characterizing other social systems with a soldier caste. The parallel caste formation in these systems, despite varying reproductive mode and taxonomic affiliation, indicates the general importance of ecological factors in influencing the evolution of social behaviour. Further, the 'recognition of self' and the defence of the infected host body from invading parasites are comparable to aspects of immune defence. A division of labour is probably widespread among trematodes and trematode species encompass considerable taxonomic, life history and environmental diversity. Trematodes should therefore provide new, fruitful systems to investigate the ecology and evolution of sociality.

Shell as an indicator of the growth rate of freshwater gastropods of the family Bithyniidae

Snails of the family Bithyniidae (Gastropoda: Prosobranchia) of 29 populations (14 014 individuals) from West Siberia were examined. Guidelines for studying the growth rate of the Gastropoda based on shells were proposed. Data on the effect of abiotic and biotic factors on the Gastropoda growth rate were analyzed. The effect of trematode parthenitae on the shell growth rate was investigated for Bithynia troscheli (Paasch, 1842).

Carbohydrate Mimicry of the Parasite in the Himasthla elongata (Trematoda: Echinostomatidae)—Littorina littorea (Mollusca: Prosobranchia) System

Using labeled lectins, a comparative study of the surface of tegument of Himasthla elongata at different stages of development cycle (daughter rediae, cercariae, and metacercariae) and glycocalyx of plasma membranes of hemocytes of molluscs Littorina littorea and Mytilus edulis that are the first and second intermediate hosts of this trematode species, respectively, has been carried out. It is found that in the course of the development cycle of the parasite there occurs a change of the set of terminal sacharides of the glycocalyx of the H. elongata tegument surface as well as differences are revealed in the pattern of binding of three out of five tested lectins with hemocytes of blue mussel and periwinkle. At the same time, the presence of similar carbohydrate determinants on the surface of hemocytes of L. littorea and daughter rediae of H. elongata is shown. The established similarity in composition of glycocalyx of hemocytes of the mollusc and the trematode parthenitae is, most likely, a result of coevolution of the parasite and the host and is of the adaptive nature. Use of the mechanism of the carbohydrate mimicry by parthenitae of this species allows them to avoid attacking by effector cells of the internal defense system of the mollusc-host.

The Effect of Trematode Parasites on the Growth of Littorina Neritoides (L.)

If the number of infections with (a) trematode parthenitae and cercariae using Littorina neritoides as first intermediate host only, and (b) encysted metacercariae using L. neritoides as second intermediate host only, are plotted against the size of the snails, two different curves result. The first shows a low rate of infection in the small size groups, but a steep upward slope rising to 91% in the large size groups. The second shows a curve increasing uniformly to 87% infection.Possible interpretations are discussed, and it is concluded that the difference is probably due to the fact that primary infections cause accelerated growth in the host.