Bychkova Е.I.¹, Efremova G. A.¹, Jakovich M. М.¹ , Fedina E.M.¹, Skuorat E.К.², Degtyarik S.M. ², Nguyen Van Duc³,Tran Thi Binh³, Rizevsky V.K.^1, Asadchaya R.L.²

¹State Scientific and Production Amalgamation « Scientific practical center of the National Academy of Sciences of Belarus for biological resources», Minsk, Belarus; ² Republican daughter unitary enterprise «Fish Industry Instite» Minsk, Belarus; ³Institute of Ecology and Biological Resources Vietnamese Academy of Sciences and Technology, Hanoi, Vietnam

Survey on the helminth fauna of the freshwater fish species of the natural reservoirs in the north of Belarus (National park "Narochansky") and Vietnam (province Thanh Hoa and Nghean Provinces)

The parasitic diseases caused by Protozoa, helminth and Crustacea widespread both in natural reservoirs and in reservoirs оf Belarus. These diseases are at the bottom of considerable decrease in rate of fish growth and its reproductive properties, development of various uglinesses and anomalies, deterioration of fish quality and death of fishes. Anthropogenous pressure on a water ecosystem leads to essential change of parasitic system «helminth – intermediate host – definitive host». It causes the rigid selection of helminth species which is carried out by adaptation to extreme conditions of environment. In such a way the favorable conditions for increase of the species diversity and parasite number with the changed of virulence are created. Well-being of reservoirs on invasion illnesses of fishes is one of the major preconditions of their rational operation.

Naroch group lakes are the largest industry reservoirs of Belarus, and also the nice places for the rest in territory of Belarus, where widespread such kind of rest as sports fishing. Carried out researches allow to estimate the structure of the ichthio complexes of Naroch group lakes, to state an estimation of a condition of the valuable trade fish species populations and the degree of contamination them by parasitic worms.

Material and methods. The full parasitologic inspection of fish from four of Naroch group lakes (Mjastro, Batorino, B.Shvakshty, Svir) has been spent. 231 specimens of seven fish species from natural reservoirs: a pike (Esox lucius L.), a river perch (Perca fluviatilis L.), a roach (Rutilus rutilus (L.), a white bream (Blicca bjoerkra (L.), a bream (Abramis brama (L.), a rudd (Scardinius erythrophthalmus (L.), a goldfish (Carassius auratus gibelio (Bloch) were surveyed. Full parasitologic inspection of fishes spent by the standard technique (Byhovskaja-Pavlovskaja, 1985). Studying of molluscs - intermediate hosts of the fish helminths - were spent in littoral zone of Naroch lake. Seven experimental plots for selection of mollusks have been chosen.

Discussion of resultes. The basic trade fish species, which raise in reservoirs of National park «Narochansky», are as traditional (a carp Cyprinus carpio L., a crucian carp Carassius carassius (L.) and a pike) and habitual in industry ponds, but atypical for natural reservoirs of republic a grass carp Ctenopharyngodon idella (Valenciennes ). The important advantage of the use of the grass carp for seeding of reservoirs is that it does not compete in a food to other fish species, and, being exclusively a phytophage, in case of correct seeding can become a regulator of a biomass of the higher water vegetation in a reservoir. Dwelling Ctenopharyngodon idella and also other representatives of the Amur-Chinese ichthyo complex - Aristichthys nobilis (Richardson), a silver carp (Hypophthalmichthys molitrix (Valenciennes), a black cupid (Mylopharyngodon piceus) - in reservoirs of Belarus leads to formation at them helminth fauna, differ from the native.

In total in the territory of Belarus 63 fish species are inhabit. Among them the basic part (29 species) is presented by Cypriniformes. In natural fresh-water reservoirs in the territory of National park "Narochansky" 25 fish species, including such valuable trade species as the European eel Anguilla anguilla (L.), a pike, European white fish Coregonus lavaretus (Poljakiw), European cisco Coregonus albula L., a carp, a tench Tinca tinca (L.) etc., from which half (12 species ) concerns to family Cyprinidea, are registered.

In the territory of Belarus 119 fish species of the parasitic worms concerning to following classes: Monogenoidea (50 species), Cestoda (18), Trematoda (36), Acantocephala (5), Nematoda (10 species) (Merkusheva, Bobkova, 1981) were registered. Among Cypriniformes the greatest specific riches of endoparasites are noted for roach (26 species), bream (24 species), rudd and white bream –20 species at every.

Among endoparasites of Cypriniformes in the reservoirs of Naroch group lakes the parasitic worms concerning to Cestoda and Nematoda (on 5 species) (table) are most richly presented. The trematoda genus Diplostomum at fishes of five species (a tench, roach, white bream, rudd, bream, goldfish) were registered. Cestoda Ligula intestinalis, trematoda Postodiplostomum cuticolа and also Tylodelphys conifera are noted at three fish species. The greatest species riches of endoparasites of National park ihthiofauna at bream (8 species) were found. For this fish species in the territory of Belarus 24 species were described (Merkusheva, Bobkova, 1981). We add to the list of the parasitic worms of bream four species (Pomphorhynchus laevis, Caryophyllaeus fimbriceps, Tylodelphys conifera, Khawia sinensis). At roach we have registered seven ectoparasite species, among which species Tylodelphys conifera, Caryophyllaeus fimbriceps, Khawia sinensis, Paradilepis scolecina earlier at this fish species (26 worm species are described) were not registered. To the list of white bream helminth (20 species of parasitic worms of fish were describe in our republic) it is possible to add the worm species Paracoenogonimus ovatus.

To twenty species of the parasites of rudd it is necessary to add helminth species Tylodelphys conifera and Paradilepis scolecina. Among the parasites of crucian carp, catch on lakes of Narochansky group, species Pomphorhynchus laevis in addition to five described parasites species of a crucian silver (Merkusheva, Bobkova, 1981) is noted.

Table. Specific riches of parasitic worms of Cypriniformes species of the fishes living in reservoirs of NP "Narochansky"

Parasitic worm species	Tench	Roach	White bream	Rudd	Bream	Carp	Goldfish
Acanthocephala
Pomphorhynchus laevis	-	-	-	-	+	-	+
Trematoda
Posthodiplostomum cuticola	-	+	+	+	-	-	-
Diplostomum sp.	+	+	+	+	+	-	+
Tylodelphys conifera	-	+	-	+	+	-	-
Rhipidocotyle illense	-	+	-	-	+	-	-
Paracoenogonimus ovatus		+	+		+	-	-
Cestoda
Ligula intestinalis	-	+	+	-	+	-	-
Caryophyllaeus fimbriceps	-	+	-	-	-	+	-
Khawia sinensis	-	-	-	-	+	+	-
Triaenophorus nodulosus	-	-	-	-	+	-	-
Paradilepis scolecina	-	-	-	+	-	-	-

On the territory of Northern Vietnam eight species of cyprinids were examined for intestinal helminthes: Carassius auratus, Cyprinus carpio, Hypophthalmichthys harmandi, Labeo rohita, Culter erythroterus, Squaliobalbus curriculus, Aristichthys nobilis, Ctenopharyngodon idella, from which in the north of the republic of Belarus in lakes of national park "Narochansky" there are four fish species: a goldfish Сarassius auratus gibelio (Bloch), a carp Cyprinus carpio L., a bighead Aristichthys nobilis (Richardson) and grass carp Ctenopharyngodon idella (Valenciennes). Because of the last fish species are introduced in our country , is not excluded a high probability of carrying of the native species of parasites on a territory of republic and to expansion of a circle of owners of parasitic worms. There are fifteen species of the intestinal helminthes of cyprinid fishes from reservoirs of Vietnam were found: four cestoda species (Caryophyllaeus fimbriceps, Khawia japonensis, Atractolytocestus sagittata, Capingens sp.), seven trematoda species (Aspidogaster decatis, Prosorhynchus sp. Asymphylodora japonica, Asymphylodora sp., Orientocreadium batrachoides, Carassoterma koreanum, Isoparorchis hypselobagri), two nematoda species of Capilaria genus , and two acanthocephalian species (Cleaveius longirostris, Acanthogyrus sp.).

In the littoral zone of Naroch lake existence of seven species of gastropods (Lymnaea auricularia, Lymnaea ovata, Lymnaea palustris, Lymnaea stagnalis, Planorbarius corneus, Planorbis planorbis, Viviparus viviparous) were established. On number in all registration plots species L. stagnalis (64,41 %) was prevailed. The species Pl. corneus (12,19 %) was a subdominant. A percentage parity of species P. planorbis, L. palustris, L. auricularia, L. ovata V. viviparus from number of all collected gastropods has made 4,84 %, 2,71 %, 7,16 %, 0,97 % and 7,72 % accordingly. The average density of mollusks in a coastal zone of the investigated lake changes in limits from less than 0,1 specimen /m² till 1.7 specimen /m².

The analysis of a specific variety of the gastropods communities of various habitats of a coastal zone of the Naroch lake has shown that the highest values of an index of specific riches (R - 3,28), an index of a specific variety of Shennon (Н - 2,01), and also an index of domination of Simpson (F - 2,01) are noted for a coastal zone of lake in vicinities of villige Stepenjovo, where all registered gastropods species are noted. Thus the index of uniformity of Pielu accepts rather low value (E - 2,36) in comparison with the values of the given indicator, calculated for other six investigated platforms, that speaks about rather non-uniform distribution of individuals among the listed of mollusk species in the received samples.

At the mollusks, which collected in a coastal zone of the Naroch lake, the larvae stages of trematoda species are registered at all seven above listed Gastropoda species. The general contamination of mollusks by larvae stages of Trematoda was 52,2 %. Representatives of the group of stylet cercaria are registered at 111 copies of gastropods (PI- prevalence of infestation- - 21,47%), from which 50 specimen was infest by cercaria fam. Plagiorchidae (PI-9,67%), and 61 – by cercaria fam. Echinostomatidae (PI - 11,80%). The larvae belonging to furcocercous group, are found out at 258 mollusks (PI 49,90%). From them 94 individuals have appeared infected by cercaria fam. Strigeidae (PI 18,18%), while in 164 representatives of investigated group of invertebrates are found out cercaria fam. Diplostomatidae (PI 31,72%). Mixed invasion by furko- and stylet cercaria at 49 Gastropoda individuals (PI 9,48%) were revealed. It is necessary to notice that at inspection of mollusks in four cases the invasion them by larvae stages of trematods fam. Shistosomatidae (PI - 0,77%) and also two cases the invasion molluscs by larvae of fam. Notocotylidae (PI 0,39%) were registered.

Thus, at the mollusks - the intermediate hosts of the fish helminthes - collected on Naroch lake, presence cercaria of six trematoda families: Plagiorchidae, Echinostomatidae, Notocotylidae, which belong to group of the stylet cercaria, and Strigeidae, Diplostomatidae, Shistosomatidae, which concern with group furko cercaria, were revealed. The general contamination of gastropods by cercaria fam. Plagiorchidae, Echinostomatidae, Strigeidae, Diplostomatidae is enough high and reach 52,22 %. The invasion of mollusks by larvae stages of trematoda fam. Shistosomatidae and Notocotylidae does not exceed 0,77 % and 0,39 % accordingly. Most often there are the mollusks infected by cercaria fam. Diplostomatidae (31,13 %). Mixed invasion by furko - and stylet cercaria registered enough seldom (PI 3-10 %%). The cercaria of poly-host type species L. ovata are noted at all infected mollusks, larvae species L. palustris and L. stagnalis - at 71,43 % and 54,05 % accordingly, for species V. viviparus, Pl. corneus, P. planorbis and L. auricularia the given indicator varies in limits from 43 to 48 %%.

In reservoirs of the National park "Narochansky" 11 species of fish parasites are registered. Among lakes the greatest specific variety is characteristic for ichthiofauna of the Svir lake (11 species). Here the highest indicators of contamination of fishes by parasitic worms (PI– 85,6 %, RI - relative intensity-8,7 specimen) also was noted. In all reservoirs the greatest infectiousness by helminth at bream was noted. The given fish species it is characteristic as much as possible high specific variety of intestinal parasite (8 species ), frequency of occurrence (PI- 82,5 %,) and their relative number among the surveyed lakes 8,5 specimen. It is necessary to note that a common species for fauna parasitic worms of fishes of the north of Belarus and Northern Vietnam is Caryophyllaeus fimbriceps (Cestoda).

References:

Byhovskaja-Pavlovskaja I.E. Parasite of fishes: a study guide. М, 1985.

Merkusheva I.V., Bobkova A.F. Gelminth of the house and wild animal of Belarus: Catalogue. Minsk:Nauka i technica, 1981. 120s.

Work is executed with the support of foundations for fundamental research of National Academy of Sciences of Belarus and Vietnamese Academy of Sciences and Technology.