DYNAMICS OF PARASITOFAUNA OF DIFFERENT AGE GROUPS OF IDE LEUCISCUS IDUS (L. 1758) OF LOWER IRTYSH

The paper aims to identify the age-related dynamics patterns of distributing the parasitofauna of ide in the Lower Irtysh. The composition of the ide parasitic community is represented by sixteen species belonging to the classes Monogenea, Cestoda, Trematoda, Nematoda, Copepoda, where Trematoda class is remarkable for the highest species diversity (9 species). It has been stated that the composition of the ide parasite fauna is distributed nonuniformly within the age groups. The study noted the presence of parasite species invading ide of any age group; there were also parasitic organisms observed either in young ide representatives, or in older fish species, as well as there were found parasite species not belonging to any distribution system. According to the analysis results of the age dynamics of the average invasion intensity, it has been found that the representatives of O. felineus and R. campanula prevailed in the number of specimens in all age groups of ide. The dynamics of the invasion extensity conditionally corresponds to three groups: EI growing with the fish aging, EI with a decreasing dynamics, constant EI = 100% (represented by R. campanula). The parasitofauna of the Lower Irtysh ide is similar to the parasite fauna of ide species inhabiting other water bodies, and shows the peculiarities of occurrence both within a separate age group and in the dynamics of occurrence parameters with fish aging

Haematophagous parasites of some fish species in the Lower Irtysh

The purpose of the research is study of four fish species infected with haematophagous parasites in the rivers of the Lower Irtysh basin. Materials and methods. The work was performed in the rivers of the Lower Irtysh basin in 2017–2020. A total of 390 fish of different sex and age were examined including 47 roach (Rutilus rutilus lacustris, (Pallas)), 41 ide (Leuciscus idus, (Linnaeus, 1758)), 47 pike (Esox lucius, (Linnaeus, 1758)) and 255 Siberian sterlet (Acipenser ruthenus marsiglii (Brandt, 1833)). We took blood from the tail artery, and examined its fresh drop under a microscope, and prepared a thin smear, then dried it in the air and fixed in a mixture of 70% ethyl alcohol and diethyl ether (1 : 1) for 30 minutes. The fixed smears were dried in the air at room temperature and stained with azure and eosin at a dilution of 1 : 10 for 40 minutes. We identified species of the found parasites and calculated the prevalence of infection with standard error of the mean.Results and discussion. We found representatives of the Coccidea and Kinetoplastea classes parasitizing in fish blood. Trypanoplasma acipenseris and Haemogregarina acipenseris were recorded in the Siberian sterlet. The pike was infected with T. schulmani and H. esoci. T. schulmani was found in the blood of the ide and roach. Piscicola geometra is the main host of flagellates and sporozoans that parasitize in fish blood in the basin of the Lower Irtysh. The roach and the Siberian sterlet become infected with parasitic flagellates from the age of 1+. All examined fish were infected in age groups 2+ – 4+. Haemogregarina parasitize in the pike aged 4+ and 5+, and in the Siberian sterlet aged 1+ – 4+ and 6+ – 7+.

SPECIES COMPOSITION AND RELATIVE POPULATION SIZE OF FISHES IN THE OSTER RIVER (THE DESNA RIVER BASIN): 50 YEARS ANALYSIS

Inroduction. Changes in the species composition and population size of freshwater fihes are determined by deformations of the habitat in Ukraine and are characterized by a pronounced negative dynamics. Deformation of ichthyofauna is caused by extinction of a number of aboriginal fihes and emergence of alien species.Aim. To establish the current species composition and relative population size of fih species in the Oster River and the dynamics of these characteristics over a 50-yearlong period in the context of negative transformations of the ichthyofauna of the rivers of Ukraine.Results. Comparative study of the species composition and relative population size of fih species in the fih catches by small-river fihing gear in the Oster river was conducted during the period since 1971-72 till 2019. During this time considerable changes in species composition took place. The following species disappeared from the catches: Leuciscus leuciscus, Leuciscus idus, Chondrostoma nasus, Carassius carassius, Blicca bojerkna and Neogobius flviatilis, they were replaced by three invasion species (Percottus glenni, Pseudorasbora parva, Proterorhinus marmoratus). The changes in the dominant species took place, thus, in the Oster ichthyocene the species with the short life cycle started to prevail, the share of invasion species increased from 1.4 to 37%, and the share of initial marine fih among them is very low. The comparison with the river systems of the Stugna and the Lower Dnipro represents the fact that the mentioned negative tendencies are common for the whole Dnipro system, however the situation in the Lower Dnipro must be considered less critical than in the Oster and the Stugna rivers. The fact that the catches of industrial fih decreased more than 10 times in the Desna river during this period of time gives the reason to consider that the dramatic reduction of the absolute number of their populations occurred in the Oster river as well. That is why even relatively safe species (Abramis brama, Rutilus ritilus, Scardinius erythrophthalmus, Esox lucius, Perca flviatilis, Alburnus alburnus, Squalius cephalus) are in critical situation in this transformed river system.Сonclusions. In the ichthyocene of the Oster River over a 50-year period there have been signifiant changes in species composition, relative and absolute population numbers associated with the extinction and reduction of population sizes of rheophilic species and fih that are adapted to life in the flodplain. The modern Oster River is dominated by invasive and short-cycle species. The obtained tendencies in the dynamics of the ichthyofauna of the Oster River are similar to the nature of changes in other river systems of Ukraine, although they occur at a faster pace, which is characteristic of the smallest plain rivers.

MORPHOLOGICAL CHANGES IN THE LIVER AT DIFFERENT INVASIVE DOSES OF OPHISTORCHIS FELINEUS (RIVOLTA, 1884) IN RODENTS (ORYCTOLAGUS CUNICULUS)

A morphometric study of liver changes at different invasive doses was conducted in rodents (Oryctolagus cuniculus). In a comparative aspect, the thickness of connective tissue formed around the portal tracts and the thickness of cellular infiltrates in the same area were studied at an invasive dose of 100, 50 and 10 metacercariae of Ophistorchis felineus (Rivolta, 1884). The experiment was conducted on sexually mature male rabbits at the age of 6 months, in each observation group of 10 individuals. Clinically healthy animals were infested with Ophistorchis felineus per os metacercariae once. The intermediate stage of the parasite was isolated from a dead fish (ide, Leuciscus idus (Linnaeus, 1758) and dace fish, Leuciscus leuciscus) obtained from the Tom River in Tomsk. The invasion that took place after 1 month was confirmed by a positive analysis of feces for parasite eggs by the Ragaser and KatoMiura methods. The animals were sacrificed after 5 weeks from the period of infestation. Histological preparations of the liver were made, stained with hematoxylin and eosin, according to Van Gieson. Histological preparations were studied by light microscopy with morphometry. The results obtained characterize a twofold change in the morphometric parameters of connective tissue thickness and cellular infiltration around the portal tracts of the liver lobes with an increase in the invasive dose.

Molecular data on Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from an intermediate host Dreissena polymorpha (Bivalvia: Dreissenidae) in the Northern Dvina River Basin, Northwest Russia

We report the first molecular identification of Phyllodistomum macrocotyle (Digenea: Gorgoderidae) from the Northern Dvina River Basin, Northwest Russia. Comparative analysis of our sequence was 100% identical to the 28S and ITS2 rDNA sequences of the species P. macrocotyle in zebra mussels discovered in Poland (Wigry Lake), Lithuania (Elektrenai Reservoir and Sirvinta River), Russia, Belarus (Lepelskoe Lake and Lukomskoe Lake), and in fish Leuciscus idus, Scardinius erythrophthalmus in Russia (Rybinsk Reservoir on the Volga River). At the same time, some sequences of the 28S rDNA of P. macrocotyle in zebra mussel detected in Lithuania, and Belarus were different from our sequence on 0.2-0.6%. The ITS2 sequences which have 100% similarity with our specimens of P. macrocotyle were discovered in sporocyst of phyllodistomes from its intermediate host D. polymorpha in Poland, Lithuania, Russia, and Belarus. Our observation in the Yuras and Isakogorka rivers represents the northernmost record of this host-specific parasite, to the best of our knowledge.

Developmental anomalies in ide (Leuciscus idus L.) larvae caused by copper and cadmium

<b>Ide embryos were incubated in 0.1 mg dm³ of Cu or Cd or in clean tap water (control). Both metals significantly decreased swelling of eggs. They reduced the rate of embryonic development and the hatching rate. Six types of body malformations were found in newly hatched larvae: spine curvature, C-shaped body, head deformation, yolk sac deformation, heart oedema, and reduced body length. Only the first two types of deformations were observed in the control, while more severe malformations were found following Cu and Cd exposure. Copper exerted a detrimental effect mainly during embryogenesis (egg swelling and rate of development), while the toxic effects of cadmium were more significant in newly hatched larvae. Larval body deformities may be used as a bioindicator of water pollution with heavy metals.</b>