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Simple Summary: The ultrastructural study of spermatozoa in parasites such as the Digenea provides data that, like classical morphological features, biological data, and genetic characterization, can help achieve a better understanding of phylogenetic relationships at different taxonomic levels. In this context, the present study provides the first ultrastructural data of spermatozoa in a digenean species of the genus Artyfechinostomum. These results increase the database of ultrastructural spermatological characteristics within the group of Echinostomatoidea. The comparison of these features with the existing data allows us to establish a coherent model of the sperm cell for species belonging to this superfamily. The study of sperm characteristics has proven useful for elucidating interrelationships in several groups of Platyhelminthes, such as digeneans. Thus, in the present work, the ultrastructural organization of the mature spermatozoon of the digenean Artyfechinostomum malayanum (Echinostomatidae), a parasite of Rattus norvegicus (Rodentia: Muridae) from Dong Thap Province, Vietnam, was investigated for the first time using transmission electron microscopy. The male gamete of A. malayanum exhibits two axonemes of different lengths, showing the 9 + '1' pattern of the Trepaxonemata, a nucleus, two mitochondria, two lateral expansions, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies, and granules of glycogen. Thus, the mature spermatozoon follows a Type V sperm model proposed for digeneans. We also highlight some noteworthy characteristics in Echinostomatidae with possible phylogenetic implications, such as two lateral expansions in the anterior region of the spermatozoon and two mitochondria. [ABSTRACT FROM AUTHOR]

We performed a detailed ultrastructural reconstruction of the "passive" miracidium of Derogenes varicus Muller, 1784 , a species from the Hemiurata group. The miracidium is highly miniaturized and simplified in comparison with the "active" miracidia. For the first time we elucidated the nature of the spines on the surface of the hemiuroid larva: they are derivatives of the epithelial plates. The anterior end of the larva is equipped with three epithelial plates that bear both spines and cilia. The major part of the miracidial surface is formed by the tegument. The nervous and excretory systems of the D. varicus miracidium are extremely reduced. Single undifferentiated cell comprises the germinal material of the miracidium. We discuss the trends of evolution of hemiuroid miracidia that are associated with the transition to passive strategy of infection. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to describe Plenivitellinum kifi n. gen., n. sp. (Digenea: Azygiidae) infecting the gastrointestinal tract of the African tigerfish, Hydrocynus vittatus Castelnau, 1861 (Characiformes: Alestidae) in the Kavango River, Namibia. We revise the diagnosis of Azygiidae Lühe, 1909 to accommodate this new species. Methods: The worm was heat-killed, fixed in 10% neutral buffered formalin, stained in Van Cleave's and Ehrlich's hematoxylins, cleared in clove oil, and mounted on glass slide using Canada balsam. Results: The new azygiid resembles species of Otodistomum Stafford, 1904 by having an elongate body, a ventral sucker that is wider than the oral sucker and that is in the anterior half of the body, a pre-testicular ovary, a uterus that primarily occupies the inter-caecal space between the ovary and the ventral sucker, and a vitellarium that is restricted to the hindbody and that is confluent posteriorly in the post-testicular region. The new genus differs from all species of Azygiidae by having the combination of a ventral sucker that is wider than the oral sucker (vs. narrower), an elongate prostatic sac that extends posteriad to near the posterior margin of the ventral sucker (vs. an ovoid prostatic sac that is wholly anterior to or slightly overlaps the anterior margin of the ventral sucker), a vitellarium that nearly fills the post-testicular space and that extends posteriad beyond the caecal tips (vs. a vitellarium that is separate posteriorly or that is restricted to the anterior half of the post-testicular space and does not extend posteriad beyond the caecal tips), and an I-shaped excretory bladder (vs. Y-shaped). Conclusion: This study documents the first record of an azygiid from Africa and the first record of an azygiid infecting a characiform fish. [ABSTRACT FROM AUTHOR]

Abstract Among parasites of the digestive tract of the black-headed gull (Chroicocephalus ridibundus) in Poland, the best known are species of digenetic trematodes and cestodes. Nematodes of this bird species are not well known. Black-headed gulls, due to their varied diet, migration, life in a flock, and changes of habitat, can become infected with various species of helminths, and like synanthropic birds, they can spread the dispersal stages of parasites across urban and recreational areas. In the present study, an attempt was made to identify the helminth fauna of C. ridibundus from breeding colonies in north-central Poland. The aim of the study was to describe the taxonomic structure of parasites of the digestive tract of the black-headed gull and determine the quantitative parameters of their occurrence. A total of 43 black-headed gulls were examined post-mortem for gastrointestinal helminths, resulting in the identification of four cestodes (Paricterotaenia porosa, Lateriporus clerci, Anomotaenia micracantha, and Wardium fusum), three trematodes (Diplostomum pseudospathaceum, Plagiorchis laricola, and Apophallus muehlingi), and three nematodes (Eucoleus contortus, Cosmocephalus obvelatus, and Porrocaecum ensicaudatum). Lateriporus clerci (in adult form), C. obvelatus and P. ensicaudatum (in larval form) were recorded for the first time in the black-headed gull in Poland.

Heterophyiasis is a highly endemic disease in the Nile Delta, Egypt, where people consume raw or undercooked Oreochromis niloticus and Mugil cephalus. Birds and rats play a crucial role in fish-borne zoonotic trematode transmission since they serve as natural and experimental hosts. This study aimed to update the epidemiological information, morphological description, molecular identification and gene expression of two distinct heterophyid metacercariae in Giza, Wadi Al-Rayan, and Lake Manzala, Egypt, whereas various heterophyid infections could be expected. The present Centrocestus formosanus, Heterophyes heterophyes, and Heterophyes nocens with accession numbers OR947651.1, OR947700.1, and OR947719.1, respectively, matched with those recorded in the GenBank. Findings of the current investigation indicated that various cytokines like IL-1β, MHC-II, and TNF-α rapidly elevated in the infected pigeon's intestines. Additionally, the infection expanded due to the parasite's ejection from the host and the host's clinical affliction, which induced humoral immune responses. Interestingly, investigation of other trematode species is in extreme demand in terms of zoonoses. We suggest controlling snails, managing migratory birds, and examining and frying fishes to the point when the encysted metacercariae is destroyed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Previous population genetic analysis of Opisthorchis viverrini eggs revealed two populations. • Cat- and human-specific populations use different intermediate fish hosts. • There are distinct morphologies in egg, metacercaria, and adult worm stages of O. viverrini. • Our study confirms distinct human- and cat-specific O. viverrini populations. Infection by the zoonotic fish-borne trematode, Opisthorchis viverrini, remains a crucial health issue in Thailand and neighboring countries. Recently, molecular analysis revealed two populations of putative O. viverrini : one found primarily in human hosts ("human-specific" population) and the other primarily in cats ("cat-specific" population). It is unclear how the infective stages (metacercariae) of these different populations circulate among definitive and reservoir hosts in nature. To gain an insight into this, mitochondrial cox 1 and nad 1 gene sequences of metacercariae from fish intermediate hosts were examined. None of 192 metacercariae from cyprinid fish in Lao PDR and Thailand had sequences typical of "cat-specific" O. viverrini , suggesting that cyprinid fish are not the main second intermediate hosts of this population. Interestingly, all 20 O. viverrini -like metacercariae from snakehead fish (Channa striata) shared 99.51–100% sequence identity with eggs from cats naturally infected in a previous study. Hence, we propose a modification of the known transmission dynamics of O. viverrini : consumption of metacercariae within snakehead fish provides another pathway for cats and (occasionally) humans to acquire infection. We also performed morphological comparisons of eggs, metacercariae, and adult flukes (raised in hamsters) of both Opisthorchis populations. The "cat-specific" population has eggs that are narrower and adults that are shorter and wider than in the human-specific population. The metacercaria of the "cat-specific" population is elliptical, while that of the "human-specific" population is oval, occasionally rounded. Our results confirmed that O. viverrini -like metacercariae from snakehead fish are the infective stages of the "cat-specific" fluke. This provides a new insight into the dissemination and transmission of each population in the second intermediate host. The identity of the cat-specific population is discussed. [ABSTRACT FROM AUTHOR]

Simple Summary: Parasitic flatworms of the family Cyclocoelidae parasitize various inner organs of birds, mainly in their respiratory and digestive systems. The taxonomic position of many cyclocoelid species remains controversial. In our study, we studied two species of trematodes from the family Cyclocoelidae (Harrahium obscurum and Morishitium dollfusi) using classical morphological and molecular phylogenetic approaches. We provided original drawings, morphological descriptions, and the results of a molecular phylogenetic analysis of these species of helminths from birds in Russia for the first time. Our work shows the morphological variability in individuals of both flatworm species. Since the variability of individual cyclocoelids may be rather high, morphological features alone are insufficient for their identification, and confirmation with the use of molecular data is required. The taxonomic status of many species of the family Cyclocoelidae is still unclear. Two species of cyclocoelids, Harrahium obscurum and Morishitium dollfusi, were collected from the air sacs of birds (Turdus merula and Tringa ochropus) inhabiting the Middle Volga region (European Russia). Here, we provide the first detailed morphological description of these cyclocoelids and combine it with the first molecular phylogenetic analysis of Cyclocoelidae from birds in Russia based on partial sequences of their 28s rDNA and coI mtDNA genes. Specimens of both flatworm species from different host individuals differ slightly in body shape and size, which probably reflects host-induced intraspecific variability. For the first time, we have shown that a stable morphological character such as the length of the vitelline fields in the studied digeneans is variable at the species level and cannot be used in their morphological diagnosis. [ABSTRACT FROM AUTHOR]

The ultrastructural spermatozoon organisation of the acanthocolpid digenean Stephanostomum bicoronatum have been described by micrographs of transmission electron microscopy (TEM). Live digeneans were isolated from the digestive tract of the Brown meagre Sciaena umbra (Teleostei: Sciaenidae), obtained from artisanal fishing off the coast of La Chebba (Tunisia Mediterranean Sea). The ultrastructural study reveals that the male gamete of S. bicoronatum is a filamentous cell tapered at both extremities, which present typical characteristics of digenean spermatozoa of the type III, namely two axonemes of the 9 + '1' pattern of trepaxonematan Platyhelminthes, nucleus, one mitochondrion, external ornamentation of the plasma membrane associated with cortical microtubules and located in the posterior part of the anterior region of the sperm cell, two parallel bundles of cortical microtubules, and maximum number of cortical microtubules in the anterior part of the spermatozoon. In addition, the male gamete of S. bicoronatum shows spine-like bodies, a large amount of glycogen granules and a posterior extremity containing only the nucleus. The results are compared and discussed according to the existing data in other digeneans, particularly with those of the family Acanthocolpidae. [ABSTRACT FROM AUTHOR]

Rastrelliger brachysoma (Bleeker, 1851), the short mackerel, is a dietary staple and of significant economic demand in Southeast Asia and Thailand. However, the demand for short mackerel has precipitated an overfishing crisis, leading to a depletion of fish stocks. Overfishing, coupled with parasitism, may result in a decline in the population of R. brachysoma. Digenetic trematode infection is prevalent in marine fish and has a considerable impact on the overall health of the fish. Here, to identify digenetic trematodes infecting R. brachysoma, we aim to determine the identity, prevalence, and intensity of digenean infections in R. brachysoma from the Gulf of Thailand. A total of 194 short mackerel were obtained from Chon Buri Province, where digeneans were isolated and identified. The molecular identity of the digeneans was confirmed using the nuclear 28S rRNA gene. Of the 194 short mackerel, 100% were found to be infected with digeneans, comprising of Lecithocladium, Prodistomum, Opechona, and Aphanurus. Lecithocladium was the most prevalent (98%) and had the highest intensity of infection (37 mean intensity), followed by Prodistomum (75% prevalence and 17 mean intensity). Our study thus presents the first evidence of digeneans infecting the economically important short mackerel from the Gulf of Thailand. The high infection rate of digenetic trematodes may have implications on the health of R. brachysoma, further driving their population decline. These data underscore the importance of safeguarding fisheries resources in the Gulf of Thailand, and downstream conservation efforts are crucial for evidence-based management decisions to safeguard the long-term sustainability of fish resources. [ABSTRACT FROM AUTHOR]

Among parasites of the digestive tract of the black-headed gull (Chroicocephalus ridibundus) in Poland, the best known are species of digenetic trematodes and cestodes. Nematodes of this bird species are not well known. Black-headed gulls, due to their varied diet, migration, life in a flock, and changes of habitat, can become infected with various species of helminths, and like synanthropic birds, they can spread the dispersal stages of parasites across urban and recreational areas. In the present study, an attempt was made to identify the helminth fauna of C. ridibundus from breeding colonies in north-central Poland. The aim of the study was to describe the taxonomic structure of parasites of the digestive tract of the black-headed gull and determine the quantitative parameters of their occurrence. A total of 43 black-headed gulls were examined post-mortem for gastrointestinal helminths, resulting in the identification of four cestodes (Paricterotaenia porosa, Lateriporus clerci, Anomotaenia micracantha, and Wardium fusum), three trematodes (Diplostomum pseudospathaceum, Plagiorchis laricola, and Apophallus muehlingi), and three nematodes (Eucoleus contortus, Cosmocephalus obvelatus, and Porrocaecum ensicaudatum). Lateriporus clerci (in adult form), C. obvelatus and P. ensicaudatum (in larval form) were recorded for the first time in the black-headed gull in Poland. [ABSTRACT FROM AUTHOR]

Renicolids are parasites of aquatic birds. Their species identification based on morphological characters is problematic. Here, we revised the composition of Renicola spp. parasitising anatids in nearshore areas of northern seas using integrated morphological and molecular data. We redescribed Renicola somateria and verified the diagnosis of R. mediovitellata. We established that the first intermediate host (FIH) of R. somateria is the mollusc Buccinum undatum, while the FIHs of R. mediovitellata are Nucella spp. molluscs. We described the intramolluscan stages of both species. Renicola somateria and R. mediovitellata formed a separate clade in the molecular trees of the Renicolidae. This finding confirms the existence of three main phylogenetic branches of renicolids, differing in the structure of adults, type of cercariae, and host range. Molecular data demonstrated an amphiboreal distribution of both R. somateria and R. mediovitellata. The former is represented by a single population in Europe and the North Pacific, while the latter forms separate populations in these regions. This may be because R. somateria actually uses not only B. undatum but also some other buccinid species with similar circum-Arctic ranges as the FIH. We discuss the roles played in the formation of digenean ranges by the vagility of the definitive host, the lifespan of the adults, and the distribution of the FIH. [ABSTRACT FROM AUTHOR]

The construction of dams and hydroelectric plants affects biodiversity in aquatic environments and can facilitate the invasion of species. Few studies assess the long-term response of parasite fauna under these events. The aim of this study was to investigate possible changes in the endoparasite composition of the invasive catfish Trachelyopterus galeatus (Linnaeus, 1766) in the floodplain of the upper Paraná River over a 27-year study period. A total of 79 fish were collected in period 1 (1993) and 31 in period 2 (2019/2020) at the same sampling points, and the endoparasites were located in the gastrointestinal system using a stereomicroscope. It was found that the development of the fish and the composition of their endoparasitic fauna changed over time. In the second period, the fish presented smaller values for mass (g) and standard length (cm) when compared to period 1. It was found that three species of endoparasites were found per period, but although the richness was the same, the composition differed, and only one digenean (Microrchis oligovitellum Lunaschi, 1987 (Trematoda: Paramphistomidae)) was shared. The Porto Primavera Dam was built upstream of the site between the sampling periods (1999) and caused a number of environmental changes, possibly being the main factor responsible for changes in components of the parasite community. Anthropic modification to an environment can cause loss of diversity and loss of ecological interactions. Through our results, we emphasize the importance of including parasite fauna in studies that assess environmental impacts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gaining parthenogenetic metacercariae (PM) led to a burst of speciation in the genus Parvatrema. • Evolution of Parvatrema with PM, the free-swimming cercarial stage was lost and the number of PM generations stabilized. • The relationship between PM and second intermediate hosts evolved from inhabiting the extrapallial space to endoparasitism. • Parvatrema with PM likely expanded from the North Pacific to the North Atlantic in the Pleistocene epoch. • Parvatrema with PM could serve as a model of early stages in digenean evolution. There are several species of gymnophallid digeneans in the genus Parvatrema that are unique in developing metacercariae that reproduce by parthenogenesis in the second intermediate host. Transmission of these digeneans takes place in coastal ecosystems of the North Pacific and North Atlantic seas. The first intermediate hosts are bivalves, the second ones are gastropods, and the definitive hosts are migratory birds. We integrated data accumulated over 25 years of research and differentiated a complex of five closely related species. They differ in the molluscan second intermediate hosts, distribution ranges, and life cycles patterns. The type I life cycle includes two generations of parthenogenetic metacercariae, followed by development of metacercariae which are invasive for the definitive host. In the type II life cycle, the number of generations of parthenogenetic metacercariae is unlimited, and they can also produce cercariae. These cercariae emerge into the environment and can infect new individuals of the second intermediate host. We conclude that the type I life cycle is a derived option that has evolved as a better fit to transmission in the unstable conditions in the intertidal zone. Another evolutionary trend in Parvatrema is transition from inhabiting the extrapallial space of the gastropod second intermediate host to endoparasitism in its mantle and internal organs. rDNA sequence analysis highlighted that Parvatrema spp. with parthenogenetic metacercariae form a monophyletic clade and suggested the Pacific origin of the group, with two transfers to the North Atlantic and colonisation of new second intermediate host species. Apparently the group formed in the late Pliocene-Pleistocene and diversified as a result of recurrent isolation in inshore refugia during glacial periods. We argue that parthenogenetic metacercariae in Parvatrema may serve as a model for early digenean evolution, demonstrating the first steps of adopting the molluscan first intermediate host and becoming tissue parasites. [ABSTRACT FROM AUTHOR]

Headwater streams are critical, fragile ecosystems that supply food and nutrients for an array of organisms that are vital to the overall health of a stream. As the dominant vertebrates in headwater streams of the southern Appalachian Mountains, plethodontid salamanders are critical to healthy headwater communities. However, a neglected feature of these ecosystems is the community of parasites that infect salamanders. The digenetic trematode Metagonimoides oregonensis uses the aquatic snail Elimia proxima as its first intermediate host and the plethodontid salamander Desmognathus amphileucus as its second intermediate host. In a series of southern Appalachian streams, we tested the hypothesis that variance in the prevalence and intensity of infection in salamander hosts is related to respective densities of the snail and salamander species. Infection prevalence was 100% across all streams. There was a strong relationship between the density of the snail host and infection-intensity level in the salamander host. However, the relationship with salamander density was not important, a finding that conflicts with the results of parasitological studies involving lentic and marine systems. The influence of this trematode on the ecology of headwater streams and the resident salamanders has been underappreciated, and a number of aspects of this relationship remain unknown. [ABSTRACT FROM AUTHOR]

The present study recorded the adult stages of two digenetic trematodes from the anterior part of the alimentary canal and pyloric caeca of two commercially important marine bony fishes belonging to the family Serranidae from the Red Sea in Egypt. They are opecoelid Cainocreadium epinepheli (Yamaguti, 1934) Durio and Manter, 1968 and Bucephalid Prosorhynchus serrani Durio and Manter, 1968 that infect areolate grouper, Epinephelus areolatus and yellow-edged lyretail, Variola louti, respectively. The incidence of infection is reported as 55.5% (5/9) for Cainocreadium epinepheli and 81.2 % (13/16) for Prosorhynchus serrani. The body of Cainocreadium epinepheli measured 2.003-3.667 (2.809) × 0.651-1.338 (0.986) (length × maximum width) while the body of Prosorhynchus serrani measured 1.664-2.210 (1.750) × 0.225-0.358 (0.287). Cainocreadium epinepheli is characterized by the presence of smooth tegument, median gonopore in the forebody, canalicular seminal receptacle, claviform cirrus sac, long excretory vesicle reaching forebody, pre-testicular intercaecal uterus, lobed ovary, non-filamentous eggs and has an extension of vitellaria into forebody. On the other hand, Prosorhynchus serrani devoids the oral and ventral suckers but has a single caecum, midbody-located mouth, conical rhynchus, pre-testicular ovary, and elongated seminal vesicle with curved proximal part of pars prostatica. The internal organs, body regions, and their ratios concerning total body length for both species were described, measured, and compared with some of the previously described species. Finally, this study postulates that it is the first time for studying surface topography using scanning electron microscopy of both species in Egypt. [ABSTRACT FROM AUTHOR]

Studies of Hirudinea species infesting elasmobranchs are scarce and scattered worldwide and they are inexistent off the Tunisian waters. In this work, we aimed to assess the occurrence of these parasites on two ray species in the Gulf of Tunis (Tunisia). Between 2017 and 2021, 254 fish specimens belonging to two Torpedinidae species (marbled electric ray, Torpedo marmorata Risso, 1810, and common torpedo, Torpedo torpedo (Linnaeus, 1758)) were examined for leech infestation. Morphological and molecular characterizations based on 18S rDNA and cytochrome c oxidase (COI) sequences allowed us to identify two leech species: Pontobdella muricata (Linnaeus, 1758) and a new Branchellion Savigny, 1822 species Branchellion tunisensis sp. n. This new species (B. tunisensis) exhibited distinctive traits unlike other Branchellion, including a transparent body marred with dark green along the abdomen and neck, long trachelosome (about 1/3 of the length of the body), distinctive two eye spots, the presence of a pair of lateral branchiae per somite except for the last 2 somites and cup-shaped posterior sucker. Molecular analysis of the 18S rDNA and COI gene fragments shows more than 10% divergence of B. tunisensis from other Branchellion spp. and high identity score of P. muricata with other sequenced isolates. This work allowed us to report the presence of P. muricata for the first time off the Tunisian coasts and to identify a new marine leech species parasitizing electric rays in the Gulf of Tunis. [ABSTRACT FROM AUTHOR]

The main goal of the current work was to describe and analyse the Digenean community structure in Sarpa salpa. A total of 114 specimens of S. salpa were collected from the Central Coast of Algeria at six localities. The fish were immediately transported to the laboratory to be examined for digeneans. From 107 of the 114 S. salpa examined, a total of 8,722 specimens of seven species belonging to three families were recovered. Among them, Robphildollfusium fractum and Mesometra orbicularis were the most prevalent and abundant species. Moreover, Lepocreadium album was found for the first time in S. salpa from the coast of Algeria, and Centroderma spinosissima and Wardula capitellata represent new parasites to the Algerian digenean fauna that infect teleost fish. The component community of these Digeneans is characterised by R. fractum as its dominant species representing 62% of the total number of collected Digeneans, as well by a Shannon diversity index (H′) and Dominance Simpson index (D) of 1.03 and 2.23, respectively. According to Spearman's correlation test, Mesometra brachycoelia and W. capitellata were negatively correlated to the host biological factors. On the other hand, R. fractum showed a positive correlation between its mean abundance and the total length of the fish. With these findings, we provided the component structure of the Digenean fauna of S. salpa and highlighted their diversity, contributing to the biodiversity of the parasitic Platyhelminthes in Algeria.

The study of the trematodes of the family Notocotylidae Lühe, 1909, is continued using an integrated approach based on new data. A new genus, Pseudonotocotylus n. gen., has been identified, and two species new to science, Notocotylus multipapillus n. sp. and Pseudonotocotylus martynenkoi n. sp., have been discovered. The life cycle and morphology of developmental stages of the new species are described, and the molecular data for nuclear (28S) and mitochondrial markers (cox1 and nad1) are presented. Sequences of cox1 and nad1 mtDNA genes were obtained for five previously studied notocotylid species for the first time. Phylogenetic relationships within Notocotylidae were inferred from the analysis of these markers, and the results obtained reveal some subtle differences in some of the notocotylid species despite their morphological similarities. Based on the differences in gene sequences among the species, two additional criteria are proposed to divide the genus Notocotylus into Notocotylus and Pseudonotocotylus n. gen. The criteria are based on, first, having the Pulmonata or Prosobranchia group of snails as the first intermediate host and, second, molecular properties, as shown by substitutions specific to genus at various nucleotide locations in alignments for 28S and cox1. [ABSTRACT FROM AUTHOR]

Simple Summary: Leptophallus nigrovenosus is a trematode parasite found in snakes that requires feeding on amphibians to acquire the parasite. Firstly, this study investigated, in detail, the sensory receptors on the cercariae of these parasites, shedding light on the adaptations that allow them to find their host species. Secondly, the metacercariae of Salamandra salamandra were studied using histology to examine inflammatory responses in the eyes and potential eye damage. This study involved collecting snails (Planorbius metidjensis) and observing the emergence of cercariae. Salamander larvae were then exposed to these cercariae, and the larvae were later examined for the presence of metacercariae. Notably, this study is the first to report the presence of L. nigrovenosus in the snail P. metidjensis, a previously unrecorded host. These findings revealed that members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus. Such infections in amphibians can lead to various eye issues, including cloudiness, inflammation, and tissue damage, ultimately affecting their survival. This research highlights the need for further investigation into trematode infections in amphibian eyes, which would provide valuable insights into their prevalence, transmission dynamics, and impact on host populations. (1) Background: Leptophallus nigrovenosus, an esophageal parasite that primarily affects water snakes of the genus Natrix, has a known life cycle that involves snail and amphibian hosts. However, the biological aspects, chaetotaxic patterns, and pathogeny of this parasite in its hosts have not been fully elucidated. (2) Methods: Snails (Planorbarius metidjensis) were collected in Spain and examined for cercaria emergence. The larvae were used to experimentally infect Salamandra salamandra, and metacercariae were isolated. Their chaetotaxy was studied using microscopy and scanning electron microscopy. The eye histology was also examined. (3) Results: The cercariae displayed distinctive morphological characteristics. The results of this study revealed three types of ciliated sensory papillae on the cercarial teguments, suggesting an adaptation for host detection and orientation. The metacercariae isolated from subcutaneous tissues showed oval bodies covered in spines. The chaetotaxy patterns matched those of Leptophallinae species. This is the first report of the presence of L. nigrovenosus in the snail P. metidjensis. Additionally, this study detected metacercariae in the eyes of S. salamandra, emphasizing the need for further research on trematode infections in amphibian eyes. (4) Conclusions: Members of the genus Salamandra can serve as secondary intermediate hosts for L. nigrovenosus, and the presence of metacercariae in amphibian eyes may have implications for the survival and habitat management of these amphibians. Understanding this parasite's prevalence, transmission dynamics, and impacts on host populations is crucial for conservation strategies. [ABSTRACT FROM AUTHOR]

Starting in October 2021, quarterly malacological surveys have been undertaken in Malawi, with the sampling of 12 specified freshwater habitats throughout a calendar year. Each survey monitors the presence of aquatic intermediate snail hosts of medical and veterinary importance. In March 2023, the alien lymnaeid species Pseudosuccinea columella was encountered for the first time in the surveys, in Nsanje District. This species identity was later confirmed upon DNA analysis of mitochondrial ribosomal 16S sequences. In July 2023, P. columella was also noted at single sites within Mangochi and Chikwawa Districts, and again in Nsanje District, with an additional location observed. Of particular importance, our sampled location in Mangochi District was directly connected to Lake Malawi, which expands the species list of invasive molluscs in this lake. While P. columella is a well-known intermediate snail host for human and animal fascioliasis, screening collected snails for trematode cercariae, alongside molecular xenomonitoring, did not yield equivocal evidence of active fluke infection. However, the newly recognized presence of this alien intermediate snail host within Lake Malawi, and along the Shire River Valley, flags a new concern in altered local transmission potential for human and animal fascioliasis. [ABSTRACT FROM AUTHOR]

Opecoeloides Odhner, 1928, is represented by 19 valid species found in marine fish, of which five have been reported in Brazil. Specimens of Opecoeloides pedicathedrae Travassos, Freitas & Bührnheim, 1966, were collected from the intestine of smooth weakfish Cynoscion leiarchus, a new host record, from off the coast of Rio de Janeiro, Brazil. They were examined using light and confocal laser microscopy. New partial sequences of 18S and 28S rDNA genes of O. pedicathedrae were obtained. Bayesian inference analysis on the partial 28S rDNA dataset resulted in a phylogram in which O. pedicathedrae formed a well-supported clade with Opecoeloides fimbriatus and Opecoeloides furcatus. The K2p distance between O. pedicathedrae and O. fimbriatus was 0.34%, with 3 divergent nucleotides; and between O. pedicathedrae and O. furcatus was 4.18%, with 38 divergent nucleotides. A Bayesian-inference phylogenetic tree based on the 18S rDNA recovered two main clades with five subfamilies. A clade of Opecoelinae showed that O. pedicathedrae was closer to Pseudopecoeloides tenuis; the K2p distance between these species was 2.14%, with 28 divergent nucleotides. The new nucleotide sequences presented inclusion of a phylogenetic analysis that can help to clarify the understanding of this complex taxon. [ABSTRACT FROM AUTHOR]

A new branchial fish parasitic cymothoid species, Elthusa phoenixsp. nov. (Crustacea: Isopoda: Cymothoidae), is described based on the ovigerous female collected from off Sohachi flounder, Cleisthenes pinetorum Jordan and Starks, 1904 obtained from Sado Island, Japan. Elthusa phoenixsp. nov. can be distinguished from all congeners by the following combination of features: body slightly twisted, elongated, dorsal surfaces smooth, 1.9 times as long as greatest width; pleon short, ∼11% body length, pleon 0.75 times as wide as pereon maximum width; cephalon symmetrical, sub-triangular 1.20 times wider than long, anterior margin rounded, turned down to form a rostrum; short uropods extending to middle of the pleotelson; pereopods 4–7 basis proximo-lateral margin with small carinate lobe; prominent fleshy lobes present on sternite of pereonite 7; antenna with 12 articles; maxilliped with oostegite lobes, and lateral margin with many plumose setae. [ABSTRACT FROM AUTHOR]

The hyperparasitism of tetracotyle metacercariae (Cotylurus sp.; Strigeidae) in trematode asexually multiplicating larval stages (sporocysts and/or rediae) within snail intermediate hosts have been perceived for years as a highly evolved mode of life strategy within trematodes, enhancing their development and transmission success. Here, we verified these data and the potential implications for the co-evolution of life strategies within the host–parasite–hyperparasite system. During complex research on the taxonomy and life cycles of trematodes of the family Strigeidae, the results showed that the phenomenon of metacercariae hyperparasitism on sporocysts/rediae within snail hosts is not uncommon in natural conditions in central Europe. However, the relatively low rate of cases of hyperparasitism within the population of snails and the lack of visible trends favouring such a life strategy suggest the accidental nature of this phenomenon. Simultaneously, we found a significantly higher prevalence and mean intensity of tetracotyles in snails without sporocysts/rediae than in snails co-infected by these larval stages and tetracotyles. These distinctions suggest negative relationships between tetracotyles and trematode asexually multiplicating larval stages within snails, with a potential impact on the structure and functioning of trematode larval infracommunities in snail intermediate hosts. [ABSTRACT FROM AUTHOR]

Cercariae of Plagiorchis spp. are frequently reported in European freshwater snails, but their true diversity is difficult to estimate due to subtle differences in morphology. We molecularly characterized 67 isolates of Plagiorchis cercariae collected from four lymnaeid snail hosts, Ampullaceana balthica, Ampullaceana lagotis, Radix auricularia and Lymnaea stagnalis in freshwater ecosystems in the Czech Republic and Poland. Based on mitochondrial cox1 and nuclear 28S sequences, ten species or species-level lineages were identified, including the first molecular evidence of P. vespertilionis from snail hosts and two species-level lineages reported for the first time. Previously undescribed species and species-level lineages are characterized morphometrically. We confirm the overlapping spatial distribution of Plagiorchis spp. in their snail hosts from Central Europe with those from Western and sub-Arctic Europe. Our results increase the known diversity of Plagiorchis spp. in Europe to 25 species/lineages in snails, but further research is needed to establish links between life cycle stages and to assess the host specificity of these parasites. [ABSTRACT FROM AUTHOR]

Strigea falconis is a common parasite of birds of prey and owls widely distributed in the Holarctic. We aimed to characterise S. falconis from Iceland via integrative taxonomic approach and to contribute to the understanding of its circulation in the Holarctic. We recovered adult S. falconis from two gyrfalcons (Falco rusticolus) collected in 2011 and 2012 in Iceland (Reykjanes Peninsula, Westfjords) and characterised them by morphological and molecular genetic (D2 of rDNA, cox1, ND1 of the mDNA) methods. We provide the first species record of S. falconis in Iceland which to the best of our knowledge is its northernmost distributional range. The presence of S. falconis in Iceland is surprising, as there are no suitable intermediate hosts allowing completion of its life cycle. Gyrfalcons are fully sedentary in Iceland; thus, the only plausible explanation is that they acquired their infection by preying upon migratory birds arriving from Europe. Our data indicate that the most likely candidates are Anseriformes and Charadriiformes. Also, we corroborate the wide geographical distribution of S. falconis, as we found a high degree of similarity between our haplotypes and sequences of mesocercariae from frogs in France and of a metacercaria from Turdus naumanni in Japan, and adults from Buteo buteo and Circus aeruginosus from the Czech Republic. The case of Strigea falconis shows the advantages of a complex life cycle and also depicts its pitfalls when a parasite is introduced to a new area with no suitable intermediate hosts. In Iceland, gyrfalcons are apparently dead-end hosts for S. falconis. [ABSTRACT FROM AUTHOR]

The ultrastructural differences are shown between the cytoarchitecture of the excretory bladder and excretory inclusions in four digenean species, two azygiids, the marine Otodistomum cestoides and the freshwater Azygia lucii , the marine derogenid Derogenes varicus and the freshwater allocreadiid Acrolichanus auriculatus. The unusual cytoarchitecture of the bladder epithelium of the azygiid digeneans, consisting along its entire length of two alternating, morphologically different zones, tegumental and cellular excretory epithelial zones, connected by septate junctions, has recorded for the first time for the Digenea and, in general, for the Neodermata. It, possible, suggests the participation of the tegumental distal cytoplasmic layer in the formation of their excretory bladder epithelium. Like most digeneans, the excretory bladder of A. auriculatus and D. varicus has a syncytial epithelial lining. Based on available literature and our own results, we can confirm the presence of the excretory corpuscles in adult marine digeneans and their absence from freshwater species, regardless of the digenean localization in their host. The present study shown that in marine digeneans, the excretory corpuscles are associated with specialized excretory cells or excretory syncytial epithelium. Ultrastructural data were obtained on the possible growth of the excretory bladder epithelium due to the migration of undifferentiated cells into the epithelial lining in studied marine species. We may assume that the bladder epithelium of marine adult digeneans specializes, in addition to the excretory function, in osmoregulatory function. [ABSTRACT FROM AUTHOR]

Objectives: The present work aims to expand the knowledge of the digenean species Prosogonotrema bilabiatum (Sclerodistomidae), a parasite of Chaetodipterus faber (Acanthuriformes) from Brazil, with an integrative taxonomic approach, using light microscopy, scanning electron microscopy, histology, and molecular biology. Methods: Forty-one digenean specimens were stained with hydrochloric carmine for morphological studies. Eleven parasites were dehydrated through a graded ethanol series, critical point dried with carbon dioxide, and coated with gold for scanning electron microscopy analysis. Four specimens were processed following histological routine and stained with hematoxylin and eosin and Gomori trichrome. DNA extracted was amplified using 28S partial primer D1–D3. Maximum likelihood and Bayesian inference were performed for phylogenetic analysis. Results: Morphometric and morphological data of the specimens studied ranged in accordance as observed in previous descriptions of the species. Observations from scanning electron microscopy and histology corroborated with those observed in stained whole mounts. Molecular analysis showed that specimens of P. bilabiatum from Brazil clustered with another two sequences of this species from different hosts and localities, with a high node support value. Conclusions: The integrative taxonomic approach allowed to record and describe new characteristics of P. bilabiatum related to the tegument, the structure and the arrangement of its tissues. The use of molecular markers confirmed that specimens identified as P. bilabiatum from different hosts and localities are all conspecific. Further studies, mainly molecular with less conserved genetic markers, should be carried out to better understand the phylogenetic relationships of Prosogonotrema with Hemiuroidea. [ABSTRACT FROM AUTHOR]

Purpose: The goal of this work was to increase the knowledge of the parasitic helminths of the Crane hawk, Geranospiza caerulescens. Methods: Two specimens of the Crane hawk were captured in Formosa province, Argentina, their viscera were preserved in 10% formalin and examined in the laboratory. Results: Helminthological analysis revealed the presence of six helminth taxa (one Trematoda, four Nematoda, and one Acanthocephala). The morphometric study of these helminths and its comparison with previous reports, allowed us to describe a new species of Parastrigea (Digenea: Strigeidae) and report new host-parasite associations and geographical records. Parastrigea labiata n. sp. is mainly characterized by having forebody not divided and two long trumpet-shaped projections of dorsal lip, which emerge through the opening. Five taxa, previously known, Synhimantus (Dispharynx) resticula, Synhimantus (Synhimantus) rectus, Microtetrameres sp., Porrocaecum sp. and Centrorhynchus sp. are briefly described. Conclusions: Previous parasitological studies on G. caerulescens were carried out on material collected between 1817 and 1955, and seven species of helminths were reported. In this study, the six taxa of helminths found constitute new host records, which shows the importance of contemporary studies about this host. All helminths found have heteroxenous life cycles and birds are infected by trophic transmission. Crane hawk's diet includes small vertebrates and to a lesser extent large arthropods. The finding of five helminth species that use invertebrates as intermediate hosts could indicate an important consumption of invertebrates. This research expands the helminthological inventory of Argentinean birds and the knowledge of the helminths of G. caerulescens. [ABSTRACT FROM AUTHOR]

Geographical distribution plays a major role in our understanding of marine biodiversity. Some marine fish trematodes have been shown to have highly restricted geographical distributions, while some are known to occur over very wide ranges; however, very few of these wide distributions have been demonstrated genetically. Here, we analyse species of the genus Schikhobalotrema (Haplosplanchnidae) parasitizing beloniforms from the tropical west Pacific, the eastern Pacific and the Gulf of Mexico (GoM). We test the boundaries of these trematodes by integrating molecular and morphological data, host association, habitat of the hosts and geographical distribution, following a recently proposed and standardized delineation method for the recognition of marine trematode species. Based on the new collections, Schikhobalotrema huffmani is here synonymized with the type-species of the genus, Schikhobalotrema acutum; Sch. acutum is now considered to be widely distributed, from the GoM to the western Pacific. Additionally, we describe a new species, Schikhobalotrema minutum n. sp., from Strongylura notata and Strongylura marina (Belonidae) from La Carbonera coastal lagoon, northern Yucatán, GoM. We briefly discuss the role of host association and historical biogeography of the hosts as drivers of species diversification of Schikhobalotrema infecting beloniforms.

The study of sperm characteristics has proven useful for elucidating interrelationships in several groups of Platyhelminthes, such as digeneans. Thus, in the present work, the ultrastructural organization of the mature spermatozoon of the digenean Artyfechinostomum malayanum (Echinostomatidae), a parasite of Rattus norvegicus (Rodentia: Muridae) from Dong Thap Province, Vietnam, was investigated for the first time using transmission electron microscopy. The male gamete of A. malayanum exhibits two axonemes of different lengths, showing the 9 + ‘1’ pattern of the Trepaxonemata, a nucleus, two mitochondria, two lateral expansions, two bundles of parallel cortical microtubules, external ornamentation, spine-like bodies, and granules of glycogen. Thus, the mature spermatozoon follows a Type V sperm model proposed for digeneans. We also highlight some noteworthy characteristics in Echinostomatidae with possible phylogenetic implications, such as two lateral expansions in the anterior region of the spermatozoon and two mitochondria.

We described a new species of elapid snake genus Bungarus from the Tenasserim Mountain Range in Ratchaburi Province, western Thailand. Bungarus sagittatus sp. nov. can be distinguished from all congeners by having the combination of 15 dorsal scale rows; 215–217 ventral scales; 48–56 undivided subcaudal; prefrontal suture 2.4–2.6 times length of internasal suture; anterior chin shields larger than posterior chin shields; head of adult uniform black while juvenile black with small dim white patches on temporal and parietal areas; dorsal body black, with 25–31 white narrow bands, white and black bands at midbody covering 1.5–3.0 and 4.5–6.0 vertebral scales, respectively; dorsal body black bands not intruding ventrals or intruding ventrals less than 0.5 times of width of outer dorsal scales; ventral surface of body immaculate white; ventral side of tail white with a row of dark brown triangular patches on middle pointing posteriorly; tail relatively long, tail length/total length 0.140–0.143. Genetically, the new species has uncorrected pairwise divergences of ≥ 8.29% of the mitochondrial cytochrome b from other Bungarus species. Currently, the new species is only known from the type locality. [ABSTRACT FROM AUTHOR]

Proterometra macrostoma is a digenetic trematode that is widely distributed in the eastern United States. The objective of this study was to assess how the cercariae of P. macrostoma within their redia in the infected intermediate snail host (Elimia semicarinata) respond during an initial 7-d exposure of their snail host to 20°C (mimicking a fall temperature), followed by a cold-water exposure of 7.5°C over a 28-d period (mimicking a winter temperature), and within a week after returning to warmer water at 20°C (mimicking a spring temperature). Specifically, we investigated whether cercarial development inside the redia ceases or continues during exposure of the snail host to a winter temperature, which was determined based on changes in the cercarial composition in each redia in the infected snails and the amount of cercarial shedding. Naturally infected snails (E. semicarinata) were collected from North Elkhorn Creek, Scott County, Kentucky, during June and July 2019. Baseline cercarial emergence was recorded over 7 d at 20°C for 55 snails with patent infections. Infected snails were then maintained at 7.5°C for 28 d and checked daily for any cercarial emergence followed by a post–cold treatment analysis of cercarial emergence over 7 d at 20°C. No cercariae were released during the 28-d cold treatment. Significantly more (mean ± SE) cercariae were released per snail during the 7 d following the cold treatment (4.60 ± 0.33) compared to the period prior to cold treatment (3.63 ± 0.35). At the termination of the experiment, 94.6% of infected snails were found to have living rediae with a mean ± SE infection intensity of 7.13 ± 0.51 rediae/snail (range 1–18). Additional sets of snails (pre–cold treatment = 4 snails; post–cold treatment = 5 snails) were dissected at the beginning of the pre– and post–cold treatment periods to observe individual cercarial populations within rediae. No significant differences were found in the average number of the 4 cercarial stages described within rediae pre– vs. post–cold treatment. These results suggest that additional cercariae within rediae mature during winter months, but this was not detectable by our staging criteria. [ABSTRACT FROM AUTHOR]

We elucidate the life cycle of Leuceruthrus stephanocauda (Faust, 1921) Womble and Bullard 2022, provide the first description of its adult, and redescribe its cercaria based on specimens infecting centrarchiform and perciform fishes and pleurocerid snails in the southeastern United States. Based on morphological and nucleotide-based (28S rRNA gene and internal transcribed spacer 2 [ITS2]) evidence, adults of L. stephanocauda infect the stomach of spotted bass, Micropterus punctulatus (Rafinesque, 1819), green sunfish, Lepomis cyanellus Rafinesque, 1819, and longear sunfish, Lepomis megalotis (Rafinesque, 1820) from Chewacla Creek (Tallapoosa River, Alabama) and mottled sculpin, Cottus bairdii Girard, 1850 (juvenile), from Raccoon Creek (Chattooga River, Georgia). The adult of L. stephanocauda differs from its congeners by having an elongated body and an asymmetrical vitellarium. The cercariae of L. stephanocauda shed from yellow elimia, Elimia flava (Lea, 1862) (Cerithioidea: Pleuroceridae) in Chewacla Creek and Moores Mill Creek (Tallapoosa River) and from Elimia caelatura georgiana (Lea, 1862) in Raccoon Creek. Naturally shed cercariae of L. stephanocauda are unique by having bilateral, discontinuous fields of black tail stem pigmentation posterior to the withdrawn distome and along the margins of the paired furcae, prominent subtriangular spines on the anterior end of the tail stem anterior and posterior to the distome, and broadly rounded to lanceolate furcae that are longer than wide and that bear numerous marginal and submarginal protuberances. Our 28S phylogenetic analysis recovered L. stephanocauda as a sister to Leuceruthrus micropteri Marshall and Gilbert, 1905, within monophyletic Leuceruthrinae Goldberger, 1911. No species of Leuceruthrus Marshall and Gilbert, 1905, has been reported previously from the Tallapoosa River. [ABSTRACT FROM AUTHOR]

Red swamp crayfish Procambarus clarkii were collected from Cattail Marsh in Beaumont, Texas and necropsied. Eight (13%) of 62 crayfish collected were infected with metacercariae of Crepidostomum cornutum. Excysted metacercariae were stained and mounted for morphologic identification or preserved for molecular analysis. Morphometric values were consistent with those reported previously in the literature. Sequences of the 28S ribosomal RNA gene were aligned with the National Center for Biotechnology Information GenBank database. Blast analysis returned a result of 99% similarity for C. cornutum. This study provides the first report of C. cornutum metacercariae infecting P. clarkii in Texas substantiated by a voucher specimen and sequence data. Molecular data from this study should prove helpful in identification of adult stages from fish and cercariae from bivalves in future studies. [ABSTRACT FROM AUTHOR]

Background In the present study, we aim to provide an inventory of digenetic trematodes (Platyhelminthes, Trematoda, Digenea) from Georgia including records from the freshwater, marine and terrestrial realms. The checklist is based on a critical review of data from 109 papers, 11 monographs and four Ph.D. theses published between 1935 and 2019 and our new records. The checklist includes information on synonymy, the host species, site of infection, geographical distribution and bibliographical references. The present data will serve as a baseline for further studies on trematodes from Georgia focused on integrative taxonomy, life-cycle elucidation, parasite ecology and epidemiology. New information We compiled data on the digenean trematode fauna of Georgia, which is represented by 186 species (of these 173 identified to species level) belonging to 108 genera, 47 families and 17 superfamilies. This is the first checklist of the digeneans of Georgia. The majority of digenean species were recorded as adults (160 species), only a small fraction being found as cercariae (33 species) or metacercariae (24 species), in their first or second intermediate hosts, respectively. Predominantly, records of trematodes (62 species) from birds were found, followed by those parasitising fish (50 species, i.e. 32 species as adults and 18 as metacercariae), mammals (33 species) and amphibians (25 species, i.e. 23 species as adults and 2 as metacercariae), with the least number of species reported from reptiles (12 species, i.e. 9 species as adults and 3 as metacercariae). Adult digeneans recorded together with another life-cycle stage (metacercariae and/or cercariae) comprised 28 species, i.e. for 15% of the total trematode species number, a part of their life-cycle is known. [ABSTRACT FROM AUTHOR]

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We generated new morphological and molecular data on some trematodes of the family Lissorchiidae from fish from the south of the Russian Far East. Four new species, including two species previously considered Parasymphylodora japonica and P. markewitschi in the Far East, were established on the basis of molecular data and morphological characteristics of adult worms and metacercariae. Molecular phylogenetic analysis based on partial 28S rDNA sequences showed that the subfamily Asymphylodorinae was monophyletic, while the subfamily Lissorchiinae was polyphyletic within the Lissorchiidae, confirming the results of previous studies on this family. All asymphylodorine trematodes from our phylogenetic analysis were sorted into several groups, which differ from each other at the intergeneric level by molecular data but could not be confidently delimited based on morphological characteristics. For this reason, we consider all trematodes from Asymphylodorinae within two existing genera, Parasymphylodora and Asymphylodora, both sensu lato. The first molecular data were generated for Asymphylotrema macrocetabulum, the type species of the genus. [ABSTRACT FROM AUTHOR]

According to the current taxonomic concept, the Аpophallinae Ciurea, 1924 is a monotypic subfamily of the Opisthorchiidae that comprises species with a median permanent ventrogenital sac containing a well-developed ventral sucker and two gonotyls. A recently formulated molecular hypothesis suggests polyphyly of this subfamily and the presence of two sibling species within one of the nominal species A. donicus Skrjabin & Lindrop, 1919. In this paper, we redescribed A. donicus s. str. and renamed A. donicus auct. non Skrjabin & Lindrop, 1919 to A. lari (Leonov, 1957) based on morphological, biological and molecular (mitochondrial cox1 gene fragments) data. The main morphological differences between species are the length of the distance between the anterior end of the body and the anterior extremity of the vitellarium as a ratio to the forebody length, and the shape of the anterior vitelline follicles. We also aimed to test the monophyly of the Аpophallinae through nuclear-ribosomal molecular markers 18S + 28S rDNA. Tree topology showed Apophallus zalophi (Price, 1932) clustered closer to Liliatrema Gubanov, 1953 than to the other Apophallus spp. As a result, we resurrect the genus Pricetrema Ciurea, 1933 that earlier was proposed for A. zalophi and abolish the Liliatrematinae Gubanov, 1953 with removal of Liliatrema into the Apophallinae. Thus, according to the updated concept, the Apophallinae contains three genera, Apophallus Lühe, 1909, Liliatrema and Pricetrema, two of which (Apophallus, Pricetrema) have the ventrogenital sac with two gonotyls and one (Liliatrema) has a genital sac without gonotyls. [ABSTRACT FROM AUTHOR]

Simple Summary: Different species of bats often inhabit the same territories but have differences in diet. Bats become infected with parasitic worms such as trematodes when they feed on insects. Fluke diversity is determined by bats' dietary breadth. The purpose of our research was to study trematode diversity in five Myotis species inhabiting Samarskaya Luka National Park. In the 2005–2007 period, we studied parasitic worms in bats and found 11 trematode species. One parasite species, Prosthodendrium cryptolecithum, was recorded for the first time in Russia. Only three fluke species were revealed in all studied bat species. Our study shows that trematode species diversity is higher in Myotis daubentonii and M. dasycneme. The trematode fauna of M. brandtii, M. nattereri, and M. mystacinus is less diverse. Our results confirm the similarity of habitats and diets among the five Myotis species and show weak competition among bats for food items. Various bat species often occupy the same habitats. Cohabitation should induce different preferences in spatial or trophic components of the bat ecological niche to reduce their competition. This determines the differences in the trematode fauna of Myotis spp. The purpose of our research was to study the biodiversity of trematodes in syntopic populations of five Myotis species in the Samarskaya Luka National Park. In the 2005–2007 period, we studied 867 bat specimens via the methods of complete helminthological dissection. In total, 11 trematode species from the families Plagiorchiidae (Plagiorchis koreanus, P. mordovii, P. muelleri, and P. vespertilionis), Pleurogenidae (Parabascus duboisi), and Lecithodendriidae (Prosthodendrium ascidia, Pr. chilostomum, Pr. cryptolecithum, Pr. hurkovaae, Pr. longiforme, and Lecithodendrium linstowi) were found in five Myotis species. Only three trematode species, P. koreanus, Pr. chilostomum, and P. duboisi, are common to all studied Myotis spp. Prosthodendrium cryptolecithum was recorded for the first time in Russia. Trematode species diversity is higher in Myotis daubentonii and M. dasycneme. The trematode fauna of M. brandtii, M. nattereri, and M. mystacinus is less diverse. The determining factor in the infection of bats with trematodes is feeding on semi-aquatic insects, possible second intermediate hosts of the parasites. The infection of bats with flukes occurs at different levels of host (Myotis spp.) abundance as a result of the realization of the main bat trophic relationships. Our results confirm the data that the ecological niches of the five Myotis species partially overlap. Analysis of the trematode fauna in Myotis spp. showed that, in the Samarskaya Luka, there may be weak competition for food items among bats. [ABSTRACT FROM AUTHOR]

Species of the genus Morishitium Witenberg, 1928 are parasites of the body cavity, air sacs, and lungs of birds. At least 14 species are considered valid, but molecular confirmation of their status is lacking. Here, we provide the first molecular data on Morishitium dollfusi isolated from their type host Pica pica, compared them with previously reported molecular data from Morishitium polonicum isolated from their type and paratype hosts, Turdus merula and Turdus philomelos, and performed extensive measurements of 511 individuals of Morishitium spp. across a broad host spectrum, at multiple infection intensities, and year-round. We analyzed the molecular phylogenetics of Morishitium spp. adults isolated from bird hosts of Czech origin and provide comparative measurements of the analyzed specimens. Based on the molecular examination of morphologically identified specimens of M. dollfusi and M. polonicum (CO1, ND1, and ITS2 markers), we propose synonymization of Morishitium dollfusi (Timon-David, 1950) with Morishitium polonicum (Machalska, 1980) (isolates of European origin). The three markers were either identical (CO1, ITS2) or formed haplotypes shared by the two species (ND1). Morphological analyses revealed a continuum of key identification features for the two above-named species, although we used specimens matching the original descriptions and isolated them from the type hosts. Therefore, Morishitium polonicum is a junior synonym of Morishitium dollfusi. Attention is needed regarding the status of East Asian isolates identified previously as M. polonicum (or M. polonicum malayense). The molecular analysis revealed that these isolates form a distinct clade, and further research is needed to produce data allowing the likely separation of the malayense clade as a separate species. [ABSTRACT FROM AUTHOR]

Prosthogonimiasis poses a threat to the reproductive system of poultry and wild birds, which are the definitive hosts of the parasite causing this disease. However, the parasite infection of the second intermediate host (dragonfly), the primary vector of this pathogen, is rarely reported. In this study, the prevalence of Prosthogonimus infection in dragonflies was investigated from June 2019 to October 2022 in Heilongjiang Province, northeast China. The species of metacercariae isolated from dragonfly were identified by morphological characteristics, molecular biology techniques, and animal infection experiments. The results showed that 11 species of dragonflies and one damselfly were identified and among six of the dragonflies infected by Prosthogonimus metacercariae, Sympetrum depressiusculum (28.53%) had the highest infection rate among all positive dragonflies, followed by Sympetrum vulgatum (27.86%) and Sympetrum frequens (20.99%), which are preferred hosts, and the total prevalence was 20.39% (2061/10,110) in Heilongjiang Province. Three species of Prosthogoniumus metacercariae were isolated, including Prosthogonimus cuneatus, Prosthogonimus pullucidus, and Prosthogonimus sp., among which P. cuneatus was the dominant species in dragonflies in Heilongjiang Province. This is the first report on the prevalence of Prosthogonimus in dragonflies in China, which provides baseline data for the control of prosthogonimiasis in Heilongjiang Province and a reference for the prevention of prosthogonimiasis in other areas of China. [ABSTRACT FROM AUTHOR]

The elucidation of life-cycles of digeneans, with their successive larval stages, is facilitated by the use of molecular markers. Samples of sporocysts containing cercariae and metacercariae belonging to Monorchis Monticelli, 1893 were collected from naturally infected bivalves, Cerastoderma glaucum (Bruguière, 1789), and adult forms of Monorchis spp. were collected from sparid fishes of the genus Diplodus. All specimens were collected in the Gulf of Gabès, southern Tunisia. The identities of the examined molluscs and fishes were determined via molecular barcoding of their COI gene. Sequences of COI and ITS1 genes were also obtained for both larval and adult stages of collected parasite specimens. Genetic sequence data generated for the collected larval specimens only differed minimally from the sequence data of adults identified as Monorchis parvus; we attribute the difference to intraspecific variation. The morpho-anatomical study showed that the different stages of M. parvus collected from the Tunisian coasts had the same morphology as those reported in European waters with a lag in maturity and lower measurements. The species is recorded and molecularly characterised for the first time off the Tunisian coasts. [ABSTRACT FROM AUTHOR]

A new cestode of the genus Raillietina alykhani sp.n. parasitizing Gallus gallus domesticus (Common Chicken) Linnaeus, 1758 reported in Larkana, Sindh Pakistan. New species was found to have different body shape, scolex, rostellum adorned with rows of hooks, suckers may or may not be armed, egg capsules and number of eggs in each capsule, shape, size and position of gonads and shape of its cirrus sac and uterus. [ABSTRACT FROM AUTHOR]

The parasite fauna of chub Squalius cephalus from the Kaytazdere-Yalakdere stream systems, Sea of Marmara basin, Türkiye, was investigated. Totally, four digenean species (Clinostomum complanatum, Tylodelphys clavata, Posthodiplostomum sp. and Ichthyocotylurus sp.), one nematode species (Rhabdochona denudata), one monogenean species (Dactylogyrus nanus) and two myxosporean species (Myxobolus sp. 1 and Myxobolus sp. 2) were identified. Overall infection prevalence, mean intensity and mean abundance were 87.0%, 22.1 ± 2.5, 16.2 ± 2.0, respectively. Myxobolus sp. 2 was the most prevalent parasite species, followed by Myxobolus sp. 1 and C. complanatum. Dactylogyrus nanus was the most abundant parasite species, followed by C. complanatum and Ichthyocotylurus sp. The species Thylodelphys clavata, Posthodiplostomum sp., Ichthyocotylurus sp., Myxobolus sp. 1 and Myxobolus sp. 2 are new parasite records for S. cephalus as well as new geographical records in Türkiye. [ABSTRACT FROM AUTHOR]

Renicolids are parasites of aquatic birds. Their species identification based on morphological characters is problematic. Here, we revised the composition of Renicola spp. parasitising anatids in nearshore areas of northern seas using integrated morphological and molecular data. We redescribed Renicola somateria and verified the diagnosis of R. mediovitellata. We established that the first intermediate host (FIH) of R. somateria is the mollusc Buccinum undatum, while the FIHs of R. mediovitellata are Nucella spp. molluscs. We described the intramolluscan stages of both species. Renicola somateria and R. mediovitellata formed a separate clade in the molecular trees of the Renicolidae. This finding confirms the existence of three main phylogenetic branches of renicolids, differing in the structure of adults, type of cercariae, and host range. Molecular data demonstrated an amphiboreal distribution of both R. somateria and R. mediovitellata. The former is represented by a single population in Europe and the North Pacific, while the latter forms separate populations in these regions. This may be because R. somateria actually uses not only B. undatum but also some other buccinid species with similar circum-Arctic ranges as the FIH. We discuss the roles played in the formation of digenean ranges by the vagility of the definitive host, the lifespan of the adults, and the distribution of the FIH.

Thread herrings (Opisthonema spp.) are economically important fish species in the Tropical Eastern Pacific. Knowledge of the parasitofauna of commercially exploited species is useful as it can increase our understanding of fish biology and ecology. However, our knowledge of the parasites of Opisthonema spp. is limited. During a fisheries exploration survey in April 2022, samples of Opisthonema bulleri and O. libertate were collected from three oceanographic stations in the Gulf of Tehuantepec in the Mexican Pacific. Parasitological analysis of these materials uncovered four parasite species: Myosaccium ecaude (Trematoda), Cribromazocraes sp. (Monogenea), Pseudoterranova sp. (Nematoda), and an unidentified crustacean of the family Pennellidae (Copepoda). All these species appeared rarely, except for M. ecaude, which reached a prevalence of 100%. The median intensity of M. ecaude infection was significantly higher in O. bulleri than in O. libertate. We analyzed the relationship between parasitic infection intensity and three host traits (fork length, body weight, and age). Only body weight showed a significant positive association with intensity. Future studies are required to analyze the possible effects of seasonality, locality, and host ontogeny on the occurrence of M. ecaude in thread herrings in the Tropical Eastern Pacific.

ABSTRACT Fish are considered one of the important sources of protein which are invaded by different parasites. This study aimed to shed light on monogenean parasites that infect fish within the family Sparidae in Saudi Arabia. A total of 30 Argyrops filamentosus specimens were collected from the Red Sea, the city of Jeddah (Saudi Arabia), and then examined for the presence of monogenean parasites. Parasitic species were isolated and studied morphologically using light microscopic examination and molecularly via the partial sequencing of the 28S rRNA gene. Only a monogenean parasitic species has been identified. This parasite is morphologically and morphometric compatible with previously Acleotrema maculatus Morsy, El-Fayoumi & Fahmy (2014), identified from Plectropomus maculatus in the Red Sea, Egypt. Phylogeny revealed that this putative diplectanid species nested well within a clade clustering Diplectanidae species, which along with morphological data, suggests it is a member of the genus Acleotrema. Query sequences showed identities of 98.92% for 28S rRNA (AF026118.1) of Acleotrema sp. This study reflects the first account of this genus as endoparasite taxa of the examined sparid fish, as well as providing novel DNA data for this species.

Abstract Background Here we provide a comparative analysis of the genetic structure of populations (based on nad1 mtDNA) of Isthmiophora melis isolated from the American mink (Neogale vison), an introduced invasive species, commonly occurring in the territory of Poland, and from the striped field mouse (Apodemus agrarius). Methods A total of 133 specimens of I. melis were obtained from naturally infected N. vison collected from six localities in Poland (108 samples) and 25 individuals of I. melis from A. agrarius. All sequences of the nad1 gene obtained during the present study were assembled and aligned. The standard statistics for haplotype composition, i.e., the number of haplotypes, haplotype diversity, nucleotide diversity, and average number of nucleotide differences, were calculated. Haplotype analysis and visualization of haplotype frequency among populations were performed using a median-joining network. Results Based on the samples collected from different localities in Poland, our study revealed that the overall genetic diversity of I. melis isolated from the American mink and of the striped field mouse do not differ significantly. The median-joining network showed that the three main haplotypes are in the centre of a star-like structure, with the remaining haplotypes as the satellites, reflecting the recent expansion of the populations. Conclusions The overall genetic diversity of I. melis isolated from the American mink and striped field mouse reveals a high level of homogeneity. Moreover, regional differences in the food composition of the definitive hosts play an important role in shaping the genetic structure of the trematode populations. Graphical Abstract