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Nematodes constitute one of the most speciose metazoan groups on earth, and a significant proportion of them have parasitic life styles. Zooparasitic nematodes have zoonotic, commercial and ecological significance within natural systems. Due to their generally small size and hidden nature within their hosts, and the fact that species discrimination using traditional morphological characteristics is often challenging, their biodiversity is not well known, especially within marine ecosystems. For instance, the majority of New Zealand's marine animals have never been the subject of nematode studies, and many currently known nematodes in New Zealand await confirmation of their species identity with modern taxonomic techniques. In this study, we present the results of an extensive biodiversity survey and phylogenetic analyses of parasitic nematodes infecting New Zealand's marine animals. We used genetic data to differentiate nematodes to the lowest taxonomic level possible and present phylogenies of the dominant clades to illustrate their genetic diversity in New Zealand. Our findings reveal a high diversity of parasitic nematodes (23 taxa) infecting New Zealand's marine animals (62 of 94 free-living animal species investigated). The novel data collected here provide a solid baseline for future assessments of change in diversity and distribution of parasitic nematodes.

Parasites can provide valuable insights into the ecology and health of their hosts and the state of the surrounding ecosystem. In this study, we describe the helminth parasite communities infecting penguin species in Otago, New Zealand (little blue penguin, Fiordland crested penguin, Snares crested penguin, erect crested penguin and yellow-eyed penguin). We investigate differences in parasite communities among penguin species, and changes over time for little blue penguins. In total, 19 parasite species representing 8 families (Desmidocercidae, Anisakidae, Acuariidae, Capillariidae, Tetrabothriidae, Heterophyidae, Renicolidae and Polymorphidae) were recorded from 121 penguin individuals. Parasite assemblages differed among penguin species, likely reflective of their differences in diet and feeding strategies. We also observed significant changes in the composition of parasite communities of little blue penguins using samples from a 30-year timespan (1993–2023). There was an overall increase in parasite diversity over time, including some species of potential disease concern, which could reflect a shift in prey availability of fish in the area. Our findings contribute to the understanding of penguin ecology and emphasise the use of parasites as indicators of ecological change.

The family Acuariidae is a speciose group of parasitic nematodes, infecting mostly birds as definitive hosts. This study focused on the characterization of two species of acuariids, collected in two different species of piscivorous birds, the European great cormorant Phalacrocorax carbo sinensis from Italy, and the pygmy cormorant Microcarbo pygmaeus from Israel. Parasites were analyzed using light and scanning electron microscopy and by amplification and sequencing of the 28S rDNA. The results of morphological and molecular analyses showed that Ph. carbo sinensis was infected by the acuariid Syncuaria squamata (12 females) and Cosmocephalus obvelatus (1 female), whereas M. pygmaeus was infected by C. obvelatus (2 males, 12 females). The present results provide new data on the distribution of acuariid parasites of piscivorous birds, the first report of Acuariidae in Israel, and the first molecular data on S. squamata and C. obvelatus , which will be useful in future epidemiological and phylogenetic studies of these widely distributed, but less molecularly studied parasites.

Brine shrimps (Artemia spp.) are aquatic crustaceans known as important intermediate hosts for a wide range of helminth species. From 2011 to 2021, 4,347 individuals of brine shrimp were collected for this study, investigating the diversity and infection rates of helminth species in Artemia spp. from hypersaline waters in southern and eastern Ukraine. Seven helminth species were found: six cestodes (Anomotaenia tringae, Eurycestus avoceti, Branchiopodataenia gvozdevi, Confluaria podicipina, Fimbriarioides tadornae, Hymenolepis s.l. stellorae) and one unidentified acuariid nematode (Acuariidae gen. sp.). All these helminths were recorded for the first time in intermediate hosts in Ukraine, although they had been known from other regions. Additionally, partial sequences of the 18S rDNA gene as well as the mitochondrial cytochrome c oxidase subunit 1 (cox1) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (nad1) genes were obtained for varying numbers of cestode and nematode isolates for the first time. The overall prevalence of helminth infection in Artemia spp. was 21.9%, and the intensity ranged from one to three specimens.

The yellow-billed cuckoo, Coccyzus americanus, is a threatened passerine bird native to North America that migrates to overwinter in South America. Although migratory birds have drawn broad attention, given their assumed role in the long-distance dispersal of parasites, studies on the helminth fauna of this cuculid are scarce. In the present study, nematodes found in the gastrointestinal tract of a specimen of C. americanus found in Belo Horizonte, State of Minas Gerais, southeastern Brazil, were characterized morphologically. Five species of gastrointestinal nematodes belonging to 4 families were identified: Synhimantus (Dispharynx) nasuta (Rudolphi, 1819) and Synhimantus (Dispharynx) resticulaCanavan, 1929 (Acuariidae), Microtetrameres sp. (Tetrameridae), and Cyrnea piayaeSandground, 1929 (Habronematidae) and Subulura halli Barreto, 1918 (Subuluridae). Except for Microtetrameres sp., all other nematodes are reported in this host for the first time. Although it is difficult to accurately determine the geographical origin of infections, it is important to note that Sy. (D.) resticula and Su. halli are reported for the first time in Brazil. Additionally, the absence of the former species infecting hosts where the widespread and generalist Sy. (D.) nasuta was found may indicate that Sy. (D.) resticula have either been overlooked in previous studies or that this nematode is rare indeed. Finally, the geographical distribution of Su. halli is greatly expanded and now includes the Americas. Aspects related to the dispersion of these parasites, both in migrating and native hosts, are briefly discussed.

Only a few comprehensive studies have been carried out on parasites in amphibians and reptiles in Ukraine. This has resulted in identifying over 100 helminth species across these vertebrate groups. However, most of the studies were performed in the 20 th century and the taxonomy of many parasites and their hosts has changed ever since, in addition to the discovery of new species and registrations of species that had not been previously known for Ukraine. In recent decades, there have been very few publications on helminths from amphibian or reptile hosts in this region. Notably, just one of these recent studies is a faunistic study, providing a list of helminths found in two species of green frogs – Pelophylax ridibundus (Pallas, 1771) and Pelophylax esculentus (Linnaeus, 1758). Therefore, it is clear that publishing datasets of modern records of helminths in these vertebrate groups, based on modern taxonomy, is an essential step in further studies of their parasitic diversity. Additionally, such study is important in terms of global climate change, the growing number of possibilities of invasion of alien species (both hosts and parasites) that might potentially become a threat to native biota and growing anthropogenic pressure on local populations of hosts that affect the parasites as well. In future, this study is planned to be used for the creation of a checklist of helminths of the herpetofauna of Ukraine. The present dataset is an inventory of various species of helminths parasitising common species of the herpetofauna in central, northern, western and southern Ukraine recorded during field studies in the 2021-2023 period. The dataset is the first one to represent the up-to-date and unified data on helminths of reptiles and amphibians of Ukraine. Previously, records of this group of organisms with reference to their hosts were presented as several separate records within the country. Currently, this is the largest dataset presenting geocoded records of non-human-related helminths in the fauna of Ukraine. It reports helminth species from 15 hosts (205 individuals), including eight amphibians and seven reptilian species found in various Ukrainian regions. A total of 47 helminth species have been documented in the research and during 2021-2023 period on the territory of northern (Kyiv and Zhytomyr), western (Lviv, Zakarpattia Ivano-Frankivsk), central (Vinnytsia, Dnipropetrovsk, Cherkasy, Zaporizhzhia and Poltava) and southern (Odesa) regions of Ukraine. The identified helminth species belong to the following phyla: Acanthocephala (Centrorhynchidae (2), Echinorhynchidae (2)); Nematoda (Acuariidae, Anisakidae, Cosmocercidae (3), Dioctophymatidae, Gnathostomatidae (1), Kathlanidae (1), Molineidae (7), Onchocercidae (1), Pharyngodonidae (1), Rhabdiasidae (6), Strongyloididae); Platyhelminthes (Diplodiscidae (1), Diplostomidae (2), Encyclometridae (1), Haematoloechidae (1), Leptophallidae (2), Macroderidae (1), Mesocestoididae, Opisthorchiidae (2), Plagiorchiidae (3), Pleurogenidae (2), Polystomatidae (3), Proteocephalidae (1), Strigeidae (1) and Telorchiidae (3)). Only some helminths in the dataset were not identified to species level. Material is stored in the collection of the department of Parasitology of the I. I. Schmalhausen Institute of Zoology NAS of Ukraine.

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 .

The cosmopolitan genus Streptocara Railliet, Henry and Sisoff, 1912 (Nematoda: Acuariidae) comprises parasites of the upper alimentary tract of aquatic and, rarely, terrestrial birds. Two species of the genus Streptocara are redescribed from Bulgaria by means of light and scanning electron microscopy: Streptocara crassicauda (Creplin, 1829), based on specimens from Larus genei, Larus minutus (Laridae) and Aythya ferina (Anatidae), and Streptocara recta (von Linstow, 1879) from Podiceps nigricollis (Podicipedidae). This is the first record of S. recta from Bulgaria. The host and distribution records of the species of the genus Streptocara are reviewed. Six species are recognised as valid. Streptocara crassicauda (Creplin, 1829), S. californica (Gedoelst, 1919), S. formosensis Sugimoto, 1930 and S. incognita Gibson, 1968, seem to be parasites well-adapted to birds of the family Anatidae (Anseriformes) and occasionally found in other birds, whereas S. recta (von Linstow, 1879) and S. longispiculata Gibson, 1968, are specialists of Podicipediformes and Gaviiformes, respectively. Streptocara indica Fotedar and Chishti, 1974, is recognised as a junior synonym of S. crassicauda, and Schistogendra oligopapillata Zhang and An, 2002, is considered as a junior synonym of Streptocara formosensis Sugimoto, 1930. An identification key to the species of the genus Streptocara is proposed.

In the years 2012-2014, carcasses of 286 birds of prey from the territory of Slovakia were examined for the presence of helminth parasites. The number of bird species in the study was 23; five belonging to the Falconiformes order, eleven to Accipitriformes, and seven to Strigiformes. A finding of Cestoda class comprehended 4 families: Paruterinidae (4), Dilepididae (2), Mesocestoididae (2) and Anoplocephalidae (1). Birds of prey were infected with 6 families Nematoda species of the Secernentea class: Syngamidae (1), Habronematidae (2), Tetrameridae (3), Physalopteridae (1), Acuariidae (1), and Anisakidae (2). Out of the Adenophorea class, the Capillariidae family (1) was confirmed. The Acanthocephala group was represented by the Paleacanthocephala class, the Centrorhynchidae family (3). Out of the Trematoda class, 12 different species of flukes were found, belonging to the Diplostomidae (5), Cyathocotylidae (1), Strigeidae (4), Opistorchidae (1), and Plagiorchidae (1) families. The most frequent helminth species infecting diurnal birds of prey was . This fluke was confirmed in one bird species from the Falconiformes order and in eight species from the Accipitriformes order. In nocturnal birds of prey, the most common finding was the acanthocephalan identified in four different host species of the Strigiformes order. In total, 23 helminth species were recorded for the first time in Slovakia.

Antechiniella septentrionalis n. sp. (Spirurida: Acuariidae) is described from the duodenum of a tundra vole, Microtus oeconomus (Pallas), collected in the Magadan region in the north-east part of Russia. It differs from A. suffodiax (Beveridge & Barker, 1975) and A. sertatum Smales, 1991 mainly in having a larger number of postcloacal papillae (5–6 pairs vs 4 pairs), a differently shaped left spicule, the disposition of precloacal papillae in two rows vs one, and oblong vs oval eggs. Other differences include the different disposition of ovaries in A. septentrionalis n. sp and A. suffodiax and the different structure of deirids in A. septentrionalis n. sp. and A. sertatum. The new species was characterized molecularly (partial sequences for 18S rRNA, 28S rRNA and cox1 mtDNA). The phylogenetic analyses performed showed the affinity of the new species to the members of the Acuariidae and other spirurid nematodes.