Digeneans of northern fur seals Callorhinus ursinus (Pinnipedia: Otariidae) from five subpopulations on St. Paul Island, Alaska

Small intestinal flukes of the genus Metagonimus (Digenea: Heterophyidae) in Europe and the Middle East: A review of parasites with zoonotic potential

The heterophyid trematode Metagonimus romanicus (Ciurea, 1915) (Digenea) is redescribed on the basis of type material from domestic dogs (Canis familiaris) in Romania, vouchers from experimentally infected cats (Felis catus) and adults recovered from golden hamsters (Mesocricetus auratus) infected with metacercariae from scales of chub (Squalius cephalus) and common nase (Chondrostoma nasus) (Cypriniformes: Leuciscidae) in Hungary. This trematode, endemic to Europe and neighbouring regions (northwestern Türkiye), was previously misidentified as M. yokogawai (Katsurada, 1912), a zoonotic parasite of humans in East Asia. However, the two species differ considerably both genetically and morphologically, e.g., in the position of the ventral sucker, the presence of the prepharynx, the anterior extent of the vitelline follicles and the posterior extent of the uterus. Metagonimus ciureanus (Witenberg, 1929) (syn. Dexiogonimus ciureanus Witenberg, 1929), described from domestic cats and dogs in Israel, is a valid species distributed in the Middle East and Transcaucasia, which is also confirmed by molecular data. It differs from all Metagonimus species, including M. romanicus, in having symmetrical testes instead of the oblique testes of the other congeners. The zoonotic significance of M. romanicus and M. ciureanus is unclear, but appears to be low in Europe, mainly because raw or undercooked, whole fish with scales are generally not consumed. Accidental infection of fishermen by metacercariae in the scales when cleaning fish is more likely, but has never been reported. Remains of cyprinoids with scales infected with metacercariae of Metagonimus spp. can be an important natural source of infection for dogs, cats, and other carnivores, which can serve as a reservoir for these parasites.

Description of new species of Trematoda from bats of Southeastern Mexico and a new classification for Brachylecithum rileyi n. comb. (Dicrocoeliidae)

To date, 23 species of trematodes have been reported in bats from Mexico. However, in some regions of Mexico, such as the Yucatan Peninsula, many species of bats do not have helminthological records. Here, we sampled bats in four localities in Southeastern Mexico from April 2017 to February 2022. Parasites were collected from the intestine of four species of bats: Pteronotus fulvus, Eumops nanus, Noctilio leporinus and Nyctinomops laticaudatus. Conventional morphological techniques and molecular tools with the 28S ribosomal gene were used to describe the helminths. We discovered that our parasites represent three new species and a new combination of trematodes. We found that the new species have morphological differences with their congeneric species, and we complement this information whit molecular data. Furthermore, we found morphological and molecular evidence that places Dicrocoelium rileyi within the genus Brachylecithum. This study points out the importance of comparing morphological and phylogenetic information.

DISTRIBUTION PATTERNS OF METACERCARIAE OF THE TREMATODA <i>APOPHALLUS </i><i>MUEHLINGI</i> (JÄGERSKIÖLD, 1899) IN UNDERYEARLINGS IN AN INVASIVE POPULATION OF <i>CLUPEONELLA CULTRIVENTRIS</i> (NORDMANN, 1840) FROM THE GORKY RESERVOIR (UPPER VOLGA BASIN)

After the successful naturalization of the prosobranch mollusk Lithoglyphus naticoides (C. Pfeiffer, 1828) and a number of associated trematodes in the Gorky Reservoir (in 2005-2015) an intensive spread of apophallesis in fish of this water body has been observed. As one of the second intermediate hosts of the trematode causing this disease, Apophallus muehlingi (Jägerskiöld, 1899), a freshwater form of the Black Sea-Caspian kilka Clupeonella cultriventris (Nordmann, 1840) was recorded. The aim of the work is to study the consequences of dispersal of C. cultriventris for the formation of large permanent foci of apophallesis in the Upper Volga. For comparison, data on the spread of this type of "black-spot" disease in the populations of C. cultriventris from the Gorky Reservoir and an unregulated area of the Lower Volga (downstream the cascade of Volga reservoirs, pelagic trawl coordinates from 47°08ʹN, 47°17ʹE to 46°51ʹN, 47°41ʹE) were used. The high rates of occurrence of A. muehlingi metacercariae (the infection prevalence P, %) are recorded in the fall along the entire area of the Gorky Reservoir: from the northernmost site near Rybinsk (58°01ʹN, 39°06ʹE) to the dam area (56°41ʹN, 43°21ʹE). It is found that the distribution pattern of A. muehling metacercariae varies in the sections of the reservoir differing in hydrological characteristics. In the middle (transitional type) section of the reservoir the prevalence of A. muehlingi metacercariae in groups of the smallest Black Sea-Caspian kilka fingerlings (with a body length of up to 45 mm), is close to the maximally possible (30.00-94.49%). In the upper (river-type) section of the reservoir, the prevalence of metacercariae in this group of fish does not exceed 24.39%. The minimum values of this indicator are found in the lower (lake-type) section of the reservoir (6.76-14.84%). Judging by the values of the abundance index and the coefficient of variation in the infection intensity, the aggregation of metacercariae is more pronounced in the groups of faster growing underyearlings and the Black Sea-Caspian kilka yearlings as compared to the groups of the smallest fingerlings. In the Black Sea-Caspian kilka fingerlings samples from the Lower Volga in 2020 reveals no statistically significant differences between the infection prevalence values (13.33-18.11%) in the different size groups. Thus, although the main second intermediate hosts of A. muehlingi are various fish species of the Cyprinidae family, in some cases the presence of C. cultriventris in the water body ecosystem can significantly increase the likelihood of apophallesis spread. In conditions of the Upper Volga, due to the high migration activity of large individuals of the Black Sea-Caspian kilka, a continuous zone of apophallesis can form without clearly defined boundaries between the individual foci of disease.

A review of molecular identification tools for the opisthorchioidea

The superfamily Opisthorchioidea encompasses the families Cryptogonimidae, Opisthorchiidae and Heterophyidae. These parasites depend on the aquatic environment and include marine and freshwater species. Some species, such as Clonorchis sinensis and Opisthorchis viverrini, have a high impact on public health with millions of infected people worldwide and have thus been the object of many studies and tool developments. However, for many species, tools for identification and detection are scarce. Although morphological descriptions have been used and are still important, they are often not efficient on the immature stages of these parasites. Thus, during the past few decades, molecular approaches for parasite identification have become commonplace. These approaches are efficient, quick and reliable. Nonetheless, for some parasites of the superfamily Opisthorchioidea, reference genomic data are limited. This study reviews available genetic data and molecular tools for the identification and/or the detection of this superfamily. Molecular data on this superfamily are mostly based on mitochondrial and ribosomal gene sequence analyses, especially on the cytochrome c oxidase subunit 1 gene and internal transcribed spacer regions respectively.

Review of metazoan parasites of the northern fur seal (Callorhinus ursinus) and the analysis of the gastrointestinal helminth community of the population on St. Paul Island, Alaska

The northern fur seal (NFS), Callorhinus ursinus (Mammalia: Otariidae), is a marine mammal species included into the IUCN Red List as the vulnerable species which population is dramatically declining. A significant amount of parasitological data collected previously and our recent data allowed us to clarify the list of NFS metazoan parasites and to perform a comprehensive analysis of the gastrointestinal helminth community. Gastrointestinal tracts from 756 NFSs (3- to 4-year-old males) were collected during the annual Aleut subsistence harvests in July-August of 2011-2014 from five separate rookeries on St. Paul Island, Alaska. Totally, 27,625 specimens of helminths and approximately 1000 nasal mites were collected and identified. Detailed analysis of the previously published and newly obtained data revealed 32 species of metazoan parasites, including trematodes (6 species), cestodes (4), nematodes (9), acanthocephalans (9) and arthropods (4). The gastrointestinal helminth community of newly studied NFSs comprised 19 species including trematodes (4), cestodes (3), nematodes (5) and acanthocephalans (7). Temporal changes in the helminth community structure were small but statistically significant. Gastrointestinal helminth infracommunities comprised from 1 to 10 species (average of 4). Small but significant correlation was found between the abundances of acanthocephalans (Corynosoma similis and C. strumosum), nematodes (Contracaecum osculatum, Pseudoterranova spp.) and cestode Diphyllobothrium tetrapterum.

An opisthorchiid concept of the genus Liliatrema (Trematoda: Plagiorchiida: Opisthorchioidea): an unexpected systematic position

Liliatrema is a small genus of trematodes consisting of two species. Its systematic position has long been debated, partly because of the confusing reports about the structure of male terminal genitalia. Here we test the phylogenetic position of the genus Liliatrema using data on complete 18S rRNA and partial 28S rRNA gene sequences obtained for Liliatrema skrjabini. We also provide a detailed description of terminal genitalia in adult specimens of L. sobolevi and metacercariae of both Liliatrema species. The results of the 28S rDNA-based phylogenetic analysis indicate that Liliatrema falls within a well-supported clade, which also includes Apophallus and traditional opisthorchiids. This clade, in turn, is nested within a well-supported clade, containing Euryhelmis, Cryptocotyle and Scaphanocephalus. In the 18S+8S rDNA analysis, Liliatrema appears as a sister-taxon to the Cryptocotyle + Euryhelmis group. The Liliatrema + (Cryptocotyle + Euryhelmis) clade is a well-supported sister-group to the traditional opisthorchiids. The morphology of the terminal genitalia of the liliatrematids also corresponds to that of the opisthorchioids. Thus, the results of our morphological and phylogenetic analyses favour an unexpected conclusion that the genus Liliatrema belongs to the Opisthorchioidea. We propose that the genera Liliatrema, Apophallus, Euryhelmis, Cryptocotyle and Scaphanocephalus belong, respectively, within the subfamilies Liliatrematinae, Apophallinae, Euryhelminthinae and Cryptocotylinae of the family Opisthorchiidae.

Galactosomum otepotiense n. sp. (Trematoda: Heterophyidae) infecting four different species of fish-eating birds in New Zealand: genetically identical but morphologically variable

Trematodes of the genus Galactosomum are cosmopolitan parasites that infect the intestines of fish-eating birds and mammals. Adults of named Galactosomum species have not been recorded from bird hosts in New Zealand, despite their cercarial stage being known from various studies of the first intermediate host, Zeacumantus subcarinatus. Here we describe a new species of Galactosomum infecting four different piscivorous birds in New Zealand: Caspian terns, red-billed and black-backed gulls and little blue penguins. Specimens from each of these hosts are genetically identical in the genes sequenced, but show considerable morphological variability. Galactosomum otepotiense n. sp. is distinguished from most other members of the ‘bearupi-group’ in having a single circle of spines on the ventral sucker, and spines, as opposed to scales, over most of the body. It is most similar to G. bearupi and G. angelae, both from Caspian terns in Australia, but differs in the relative sizes of the reproductive organs and in the possession of a very long forebody. Molecular data confirm that G. otepotiense is not conspecific with G. bearupi, but 28S and ITS2 phylogenies show its close relationship to G. bearupi and other Australian species. We use the cox1 sequence to confirm identity with the larval stage infecting Z. subcarinatus, as previously described in the literature. We discuss briefly the relationships between Australian and New Zealand Galactosomum spp. and their hosts, variability between genetically identical specimens found in different hosts and their potential for harm to mariculture economy.

Heterophyid trematodes (Digenea) from penguins: A new species of Ascocotyle Looss, 1899, first description of metacercaria of Ascocotyle (A.) patagoniensis Hernández-Orts et al. (2012), and first molecular data

Two species of heterophyid trematodes were found in the Magellanic penguin, Spheniscus magellanicus (Forster), from Patagonia, Argentina. Ascocotyle (Ascocotyle) patagoniensis Hernández-Orts et al. (2012) is re-described based on new, properly fixed specimens (original material from South American sea lion, Otaria flavescens Shaw, was from frozen hosts). Metacercariae of this species are reported and described for the first time from the heart of the silversides, Odontesthes argentinensis (Valenciennes) and O. smitti (Lahille), from Patagonia. Ascocotyle (Phagicola) cameliae n. sp. is described from the intestine of S. magellanicus. The new species is placed into the subgenus Phagicola Faust, 1920 because of the presence of a single row of circumoral spines and uterine loops and vitelline follicles being confined posterior to the ventral sucker. However, it differs distinctly from other members of this subgenus by the number (19-24) and length (23-31 μm) of massive circumoral spines and by the morphology of the ventrogenital sac with a large, simple gonotyl devoid of refractile bodies. Molecular data (partial 28S rDNA sequences) for both species are also provided. Matching sequences from metacercarial and adult stages helped elucidate partially the life-cycle of A. (A.) patagoniensis. The interspecific relationships and phylogenetic position of Ascocotyle were further assessed on a broad phylogeny on the Opisthorchioidea Looss, 1899. Ascocotyle (P.) ornamentata Shalaby et al. (1993) described from decomposed worms (all circumoral spines were detached) found in a dog in Egypt, with no type-specimens of this species deposited in a repository collection, is considered to be species inquirenda.

Metazoan parasites of California sea lions (Zalophus californianus): A new data and review

The population of California sea lion Zalophus californianus (CSL) has steadily increased during the last several decades. Despite extensive research addressing CSL biology and ecology performed during the last decades, there has been a minimal number of published papers documenting their parasite fauna. Our objective was to analyze the actual list of the metazoan parasites reported from CSLs and add new data on the age-related differences in the prevalence and biodiversity of the parasite community. There have been 33 species recorded but this study considers only 24 of them valid. Among them, 11 species are specific parasites of CSLs and 13 species are not specific. Additional species represent accidental infections or misidentifications. In total, 6653 helminths and 847 mites were collected and identified from 34 CSLs for this study. Six species of nematodes, Anisakis simplex sensu lato s. l. (prevalence 41%; intensity 7.6), Contracaecum ogmorhini s. l. (38%; 269.6), Pseudoterranova decipiens s. l. (29%; 33), P. azarazi (9%; 2.7), Acanthocheilonema odendhali (15%; 3.5) and Parafilaroides decorus were found. Two species of cestodes, Diphyllobothrium sp. (38%; 8.5) and Anophryocephalus sp. (15%; 14.6) represent novel undescribed species. Two species of trematodes, Apophallus zalophi (18%; 19.7) and Zalophotrema hepaticum (12%; 39.2), and five species of acanthocephalans, Corynosoma obtuscens (68%; 100.8), C. strumosum (53%; 4.6), Andracantha phalacrocoracis (3%; 1), Andracantha sp. (9%; 4.3) and Profilicollis altmani (6%; 8.5) were found. Mites Orthohalarchne attenuata (prevalence 85%) were found in the nasal cavity, while O. diminuata (21%) parasitized in the trachea and bronchi. The highest levels of infection with nematodes and trematodes were found in adult CSLs (3-16 years old), whereas the highest level of infection with acanthocephalans was found in young CSLs (pups and yearlings).