Checklist of the parasites of European eel Anguilla anguilla (Linnaeus, 1758) (Anguillidae) in Poland

The present paper lists all parasite species of the European eel Anguilla anguilla (Linnaeus, 1758), recorded in Poland, in both its saltwater and freshwater habitats. The list has been drawn up, based on data acquired since 1844. The majority of included parasite species are presented with fish infection parameters together with data on their developmental stages and occupied microhabitats, localities and dates of collection of the eels themselves. The database includes 62 parasite taxa (including 50 species, nine identified to the genus level and three to higher taxa), representing at least 47 genera and 39 families. The most frequently-noted parasites of the European eel are the cestode Bothriocephalus claviceps, the nematodes Anguillicoloides crassus, Camallanus lacustris and Raphidascaris acus and the acanthocephalan Acanthocephalus lucii. Four alien species have been noted from this host: A. crassus, the monogeneans Pseudodactylogyrus anguillae and Pseudodactylogyrus bini and the acanthocephalan Paratenuisentis ambiguus. The present list includes both new host records and earlier records not included in previous lists of parasites of eels.

HELMINTH FAUNA OF MAIN COMMERCIAL FISH IN LAKE ECOSYSTEM OF THE NAROCHANSKY NATIONAL PARK (REPUBLIC OF BELARUS)

The composition of the helminth fauna of the main commercial fish species in the lake ecosystem of the Narochansky National Park was determined. It is represented by 10 species of helminths having a complex development cycle with the participation of intermediate hosts, as well as 1 species of helminths (Gyrodactylus sp.), a representative of cl. Monogenea, having a direct development cycle. It was noted that the highest level of invasion was typical for larvae of trematodes Tylodelphys conifera. The greatest variety of parasitic helminths is observed in fish from lake Miastro and Naroch (7 species of helminths each). It was revealed that the most common representatives of the helminth fauna of fish inhabiting the lakes of Narochansky National Park are metacercariae of trematodes of the Diplostomum genus. They were found in fish in all water reservoirs examined. Their host spectrum was also the widest. Examination of the three-spine stickleback showed a severe damage by plerocercoids Ligula intestinalis (prevalence 92% to 98.4%, infection intensity 1–4 pairs per fish). In addition, proboscis worms Acanthocephalus lucii were found in the intestines of the three-spine stickleback. The trematode fauna of fish muscles from the Naroch lake group is rather poor and represented by three types of helminths: Rhipidocotyle illense, Paracoenogonimus ovatus and Apophallus muelingi.

ПАРАЗИТОЦЕНОЗ СУДАКА (Sander lucioperca) КУРШСКОГО ЗАЛИВА

Паразитофауна судака водоемов Калининградской области изучалась фрагментарно, и данные о ней носят устаревший характер. Для оценки ихтиопатологического состояния рыбы необходим постоянный мониторинг изменений в составе паразитофауны и показателей зараженности. Проведены четырехлетние исследования паразитофауны судака, обитающего в российской части Куршского залива (Балтийское море). У судака обнаружено 18 видов паразитических орга-низмов: миксоспоридии Myxobolus dispar; микроспоридии Glugea luciopercae; моногенеи Ancyrocephalus paradoxus; цестоды Triaenophorus nodulosus, Diphyllo-bothrium latum; трематоды Bunocotyle cingulate, Diplostomum spathaceum, Tylodel-phys clavata, Bunodera luciopercae, Azygia lucii, Ichthyocotylurus platycephalus, I. variegatus, Bucephalus polymorphus; нематоды Raphidascaris acus, Camallanus lacustris; скребни Acanthocephalus lucii, Corynosoma strumosum; паразитические ракообразные Achtheres percarum. Полный паразитологический анализ проводился по методике, разработанной И. Е. Быховской-Павловской. В паразитоценозе судака преобладают паразиты со сложным жизненным циклом (со сменой промежуточных хозяев). Так, в 2016 г. их доля составила 76,5 % (13 видов); 2017 – 73,4 (11); 2018 –71,4 (10); 2019 – 73,4% (11 видов), тогда как с прямым циклом развития в 2016 г. было 23,5%; 2017 – 26,6; 2018 – 28,6; 2019 – 26,6% (по четыре вида в каждом исследуемом году) паразитов. Повышение зараженности судака трематодами может указывать на процессы эвтрофикации в водоеме. За четыре года исследований наблюдались значительные различия в составе паразитофауны и экстенсивности заражения отдельных видов паразитических организмов. Ос-новной путь заражения паразитами со сложным циклом развития – трофический. Представители класса трематод доминируют в паразитофауне судака Куршского залива (восемь видов). Наибольшая экстенсивность инвазии зарегистрирована у моногенеи Ancyrocephalus paradoxus (100% в 2019 г.), метацеркария трематоды Ichthyocotylurus platycephalus (100% в 2019 г.) и паразитического ракообразного Achtheres percarum (100% в 2016-2019 гг.).

Gastrointestinal helminth fauna and helminth communities of bleak (Alburnus alburnus, L. 1758) from lower section of Danube River

The present study presents the results from examinations of bleak’s endohelminth species and structure of helminth communities from the Bulgarian part of the Lower Danube River. In 2015 and 2016, on a seasonal manner, 91 specimens of Alburnus alburnus (Linnaeus, 1758) (bleak) were examined with standard techniques for parasites. Five species of parasites: Nicolla skrjabini (Ivanitzky, 1928), Ligula intestinalis (Linnaeus, 1758), Acanthocephalus lucii (Müller, 1776), Pomphorhynchus laevis (Müller, 1776) and Contracoecum microcephalum (Stossich, 1890), larvae were identified. The analysis of the dominant structure of the found parasite species is presented to the component and infracommunities levels. All parasite species were accidental for the parasitic communities of examined fish with the exception of P. laevis and N. skrjabini. P. laevis was a core parasite species and N. skrjabini was a component parasite species for the helminth communities of bleak. The parasite communities of A. alburnus were discussed and compared with previous research data on parasite communities of bleak from River Danube in Bulgaria. New data for helminths and helminth communities of A. alburnus from Danube River (biotope Vetren) and their seasonal occurrence are presented.

ACANTHOCEPHALUS AND NEMATODES OF FISH IN WATER BODIES OF THE SYRDARYA RIVER MIDSTREAMS

The features of the nematode and acanthocephalus fauna of Cypriniformes and Siluriformes fish, their distribution in the water bodies of the Syrdarya River midstream were studied. In total, 18 helminth species belonging to the classes Nematoda – (14 species) and Acantocephala – (4) are registered in the region. 7 species we marked for the first time for the region of under consideration.Studies were conducted of different types of water bodies of the Syrdarya river in 2016–2019 years. The collection and study of helminths of fish were carried out by known methods in helminthology and ichthyoparasitology. 1239 copies of Cypriniformes fish belonging to 15 species (Cyprinidae – 12 species, Cobitidae – 3) and 12 specimens of Siluriformes fishes from the families (Siluridae and Clariidae) were researched.According to preliminary data, 18 species of helminths belonging to the class Nematoda (14 species) and to the class Acantocephala (4 species) were found in the studied fish orders in the reservoirs of the region. Significant species diversity is characterized by the class Nematoda. We have registered 14 species belonging to 4 orders. The detachment Trichocephalida Skrjabin et Schulz, 1928 is represented by one species – Capillaria tomentosa Dujardin, 1843, which is noted in most Cypriniformes in the natural and artificial reservoirs of the northeast of Uzbekistan. The greatest species diversity is distinguished by the detachment Spirurida Chitwood, 1933. We noted 8 species. The remaining units are represented by 1–2 species – banal fish parasites. The findings of Dioctophyme renale Goeze, 1782 (larvae) in Cypriniformes in the studied region should be noted.The Acanthocephala class is represented by 4 species: Neoechinorhynchus rutileMüller, 1780, Pomphorhynchus laevis Müller, 1776, Acanthocephalus lucii Müller, 1776 and A. anguillae Müller, 1780. Nematodes are dominant. The results suggest that the most optimal conditions for the functioning of the corresponding helminth communities probably exist in the water bodies of the Syrdarya’s midstream. The abundance of a number of invertebrate groups, the inhabitants of aquatic ecosystems, which are intermediate hosts of parasites, the accumulation of waterbirds and mammals contribute to the irreversible circulation of helminths in aquatic cenoses of the study area. All this requires systematic monitoring of fish helminthiasis in order to develop preventive measures.

PIKE’S (ESOX LUCIUS) PARASITOPHAUNA OF THE RIVER VYATKA

This study aims to study the pike (Esox lucius) parasitic fauna in the Vyatka River of the Kirov region. Studies were conducted at two sites in the middle of the river Vyatka in 2016–2018 The distance between them is 300 km. A total of 26 individuals were investigated. Caught specimens of fish were examined for the presence of parasites in accordance with generally accepted methods. Over the entire period of studying the pike parasite fauna in the Vyatka River, 24 different parasite species were recorded by various researchers. As a result of our research, 9 species of parasites were recorded, trematodes – 1 species – Azygia lucii, cestodes – 1 species - Triaenophorus nodulosus, nematodes – 2 species – Сamallanus lacustris, Raphidascaris acus, proboscis worm – 3 species – Acanthocephalus anguillae, Acanthocephalus lucii, Neoechinorhynchus rutili, crustaceans 1 species – Ergasilus sieboldi and glochidia 1 species – Anodonta cygnea. The total infection of pike with all kinds of parasites was 100%, with intestinal species – 66.6%. The high extensiveness of invasion is marked by crustaceans Ergasilus sieboldi – 73.1%. The study provides a comparative analysis of the parasite fauna of the common pike in the Vyatka River over 80 years. There is a tendency to reduce the species diversity of pike parasites from 24 species to 9, the disappearance of some species and the acquisition of new ones – proboscis worm Acanthocephalus anguillae with extensiveness of invasion – 15.4%, intensity of invasion – 5.3 specimen, abundance index – 0.81 specimen. The results obtained allow us to conclude that there is a significant decrease in the species diversity of pike parasites, which is probably due to the influence of the anthropogenic factor.

Influence ofTriaenophorus nodulosusplerocercoids (Cestoda: Pseudophyllidea) on the occurrence of intestinal helminths in the perch (Perca fluviatilis)

Concurrent infections of helminths in vertebrates are widespread and may demonstrate synergistic, antagonistic or negligible levels of interactions between species that share a common site. However, indirect interactions between species that occur in different organs of a host are poorly documented, particularly in fish. Plerocercoids ofTriaenophorus nodulosusare common liver infections of European perch (Perca fluviatilis). These larval cestodes cause extensive liver damage, resulting in systemic pathologies that include alteration of the physiochemical environment of the intestine. Perch harbour a wide range of intestinal helminths whose occurrence may be potentially influenced by the concurrent presence ofT. nodulosusplerocercoids. The present study, using an existing dataset, investigated the effects ofT. nodulosuson the infection levels of four common perch helminths –Acanthocephalus lucii, Camallanus lacustris, Proteocephalus percaeandBunodera luciopercae. The prevalences ofA. luciiandC. lacustriswere significantly reduced in fish infected byT. nodulosus, although the mean intensity of infections remained unaffected for any helminth species, while the mean abundance ofC. lacustriswas significantly reduced in plerocercoid-affected perch. Differences in site selection and individual interactions between the four helminth species in the intestine ofT. nodulosus-infected and non-infected perch were rarely observed.