PARASITOCENOSES OF FISH IN RIVERS AND RESERVOIRS OF THE RYAZAN REGION

The wide distribution of trematodes and other helminths with a complex biological cycle in the reservoirs of the Ryazan Region indicates an increase in the level of their eutrophication. We performed a complete helminthological study of the ide (25 copies), roach (21 copies), and perch (29 copies) according to K.I. Skryabin. Taking into account complex hydrological indicators (species composition of higher plants, microphytes, fauna of hydrobionts and their parasites), the Pra River is a dystrophic water body, the Pronya River is an eutrophic water body, and the Novomichurinsk Reservoir is a hypertrophic water body. Parasites of Pra River were represented by nine species, the Pronya River by four species, and the Novomichurinsky Reservoir by six species. Trematodes dominate in all reservoirs of the Ryazan Region. We found an endemic focus of opisthorchiasis in the Pra River where the infection of the ide with metacercarias Opisthorchis felineus reaches 38–50% with an invasion intensity of up to 70 specimens. A number of species of trematodes (Ichthyocotylurus spp., Paracoenogonimus ovatus, Diplostomum spp., Posthodiplostomum spp., Tylodelphys clavata) and cestodes (Ligula intestinalis) should be considered as indicators for assessing an increase in concentration of dissolved biogenic substances in the water bodies. There is a direct correlation between the infection of fish with the above species of trematodes and cestodes (tapeworms) being indicators of the invasion intensity and the degree of eutrophication of the reservoirs.

Parasite fauna of Golden Grey Mullet Liza aurata (Risso, 1810) collected from Lower Kızılırmak Delta in Samsun, Turkey

The mugilids are among the most cosmopolitan teleost fishes and they are widely distributed in fresh, brackish and coastal marine waters of the tropical and temperate regions of the world. Liza aurata is one of eight mugilid species survive in Turkish waters. Parasite fauna of the golden grey mullet Liza aurata (Risso, 1810) collected from Lower Kızılırmak Delta in Samsun, Turkey were investigated in the present study. Standard parasitological investigation methods were applied and standard indices of infection were calculated. A total of 10 parasite species were identified and they are; Trichodina puytoraci, Trichodina lepsii, Ligophorus mediterraneus, Ligophorus cephali, Microcotyle mugilis, Ascocotyle (Phagicola) longa, Haplosplanchnus pachysomus, Tylodelphys clavata, Neoechinorhyncus agilis and Ergasilus lizae. Overall infection prevalence was 100 % and both the mean intensity and abundance values were 190.09 ± 43.15 parasites per infected/examined fish. Ligophorus-group parasites were the most abundant (97.83 %) and Tylodelphys clavata was the least (4.35 %) among all parasite species identified. Water temperature (C), dissolved oxygen (mg/lt), salinity (ppt) and nitrate (mg/lt) values were also presented. According to results obtained in the present study, Ligophorus cephali, Ligophorus mediterraneus, Thylodelphys clavata and Ascocotyle (Phagicola) longa are new parasite records for L. aurata and Ligophorus mediterraneus, Ligophorus cephali and Ergasilus lizae are the new parasite records for Turkish parasite fauna of fish in Turkey.

The helminth community of the sand smelt (Atherina boyeri Risso, 1810) from Lake Iznik, Turkey

Metazoan parasites of the sand smelt Atherina boyeri Risso, 1810 in Lake Iznik were studied. A total of 271 specimens of A. boyeri, 208 female and 63 male, mean ( ± SD) total length 8.4 ± 2.2 cm (range 3.1–12.2 cm) and mean total weight 4.7 ± 3.5 g (range 0.1–11.7 g) were examined between June 2008 and May 2009 at monthly intervals. In 33 fish no parasites were found. In the other fish, four parasite species were recorded: Diplostomum sp. (prevalence 39.13%, mean intensity 3.50 ± 3.03); Tylodelphys clavata (prevalence 74.16%, mean intensity 10.41 ± 14.89); Bothriocephalus cf. acheilognathi (prevalence 40.59%, mean intensity 31.83 ± 57.74); and Eustrongylides excisus (prevalence 6.64%, mean intensity 1.16 ± 0.39). The mean abundance of Diplostomum sp., T. clavata and E. excisus was higher during the winter and early spring months. In contrast, the mean abundance of B. cf. acheilognathi was higher in the summer and autumn months. This distribution of the parasites was related to a change in the environment of A. boyeri from the pelagic zone to deeper water at the end of autumn and a change in food supply.

Parasites of carp bream, Abramis brama, from Lake Jamno, Poland

A total of 40 carp bream, Abramis brama (L.) from Lake Jamno were examined for their parasites in May 2002. Lake Jamno is a brackish-water coastal lagoon, strongly eutrophied and polluted by communal and industrial sewage from the city of Koszalin. The survey yielded 15 parasite species, representing different systematic groups, including 7 monogeneans Dactylogyrus auriculatus, D. falcatus, D. wunderi, D. zandti, Gyrodactylus elegans, Gyrodactylus sp., Diplozoon paradoxum; 4 digeneans (at the stage of metacercaria) Diplostomum sp., Tylodelphys clavata, Ichthyocotylurus platycephalus, I. variegatus; 1 cestode Caryophyllaeus laticeps; 2 crustaceans Ergasilus sieboldi, Argulus foliaceus; and 1 hirudinean Caspiobdella fadejewi. Monogeneans constituted the most abundant parasite group, accounting for 61.5 % of all parasite individuals collected. They were followed by the cestodes (20.7 %), digenean flukes (16 %), crustaceans (0.7 %), and leeches (0.2 %).

Interspecific interactions between larval digeneans in the eyes of perch,Perca fluviatilis

The changes in prevalence and abundance of the three species of metacercariae in the humour of the eyes of perchPerca fluviatilisin Slapton Ley, Devon, have been monitored over a period of 29 years. Earlier studies had revealed thatDiplostomum gasterosteiwas originally the sole occupant of this niche, butTylodelphys clavatacolonised in 1973 andT. podicipinain 1976. A decline in the number of perch with heavy infections ofD. gasterosteiwas significantly negatively correlated with population abundance ofT. clavataand a decline in recruitment rate ofD. gasterosteicoincided with the population increase inT. podicipinaover the period 1976–1979. It was suggested that the decline in population size ofD. gasterosteiwas due to inter-specific competition, but this hypothesis could not be tested experimentally. Subsequent investigations, reported here, confirmed the decline when the data set was extended to 1985. A severe decline in the perch population over the winter of 1984/1985 resulted in the disappearance ofD. gasterosteiandT. podicipinaand this was followed by a slow recovery from 1990 onwards. This natural experiment provided an opportunity to test the hypothesis. OnlyT. clavatasurvived throughout the perch crash and the population continued at pre-crash levels up to 1999. Its congenerT. podicipinadid not re-appear until 1994 and was probably a re-introduction: it did not attain pre-crash levels until 1999. It is likely thatD. gasterosteisurvived the crash as it re-appeared in 1991, but was confined to young of the year fish and barely approached pre-crash levels even in 1999. Its continual low levels cannot be explained by changes in the lake or in densities of snail intermediate or bird definitive hosts. New data revealed that the suspensory ligaments of the eye were the preferred site of all three species and that the eye was partitioned out between them. The data from the post-crash period do not refute but rather confirm earlier conclusions that inter-specific competition is responsible for the decline inD. gasterosteiand this remains the preferred hypothesis.