The nematode superfamily Dracunculoidea includes 166 recognized species, of which 150 (90%) are parasitic in about 300 species of freshwater, brackish-water and marine fishes. Fish dracunculoids are placed in 31 genera (86% of all dracunculoid genera) belonging to eight of the nine dracunculoid families: Anguillicolidae, Daniconematidae, Guyanemidae, Lucionematidae, Micropleuridae, Philometridae, Skrjabillanidae, and Tetanonematidae; the genus Lockenloia is considered incertae sedis. Because of difficulties in studying fish dracunculoids, associated with their morphological and biological peculiarities, most species of these largely histozoic parasites are poorly known and males of the majority of species and of eight genera have not yet been discovered. It is apparent that the present classification system of dracunculoids as a whole does not reflect phylogenetic relationships and a taxonomic revision of this nematode group, based on detailed morphological (including SEM and TEM), life history and molecular studies of individual species, is quite necessary. Data on the biology of fish dracunculoids is scarce. In known cases, their life cycles involve copepods, ostracods or branchiurids as intermediate hosts and, sometimes, fish paratenic hosts are known to occur in dracunculoid species parasitizing as adults piscivorous definitive hosts. However, nothing is known about the life cycles of representatives of 20 genera. Some species of dracunculoids, particularly of philometrids, are highly pathogenic and are known as agents of serious fish diseases. During recent years, especially the importance of Philometra spp. parasitizing the gonads of many species of marine fishes has increased due in particular to the rapid development of marine aquaculture, because they may significantly decrease fish reproduction or even cause full parasitic castration. Therefore, further detailed studies on fish dracunculoids are significant not only from the theoretical viewpoint, but they may also have practical implications.

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Abstract. About 300 species belonging to four superfamilies (Gnathostomatoidea, Habronematoidea, Physalopteroidea and Thelazioidea) of the nematode suborder Spirurina are known as the adult parasites of freshwater, brackish-water and marine fishes. They are placed in four families, of which the Gnathostomatidae, including Echinocephalus with a few species and the monotypic Metaleptus, are parasites of elasmobranchs, whereas Ancyracanthus contains one species in teleosts; the Physalopteridae is represented in fish by four genera, Bulbocephalus, Heliconema, Paraleptus and Proleptus, each with several species in both elasmobranchs and teleosts. The majority of fish spirurines belongs to the Rhabdochonidae, which includes 10 genera

The occurrence of 2 helminths is reported in eel from 3 regions of the Federal Repubhc of Germany Both specles, Angudhcola crassus (Nematoda Dracunculoldea) and Paratenuisentis ambjguus (Acanthocephala, Tenuisentidae) were recently lntroduced Into Europe, probably from Japan and the USA, respecbvely The morphology of A crassus differs from the onglnal descript~on In a few features Syntype speclmens from Japan however, showed that speclmens from Japan and from Germany are conspecif~c The morphology of P ainbiguus (flrst report from Europe) corresponds xvell

Abstract:The larval development of the nematode Contracaecum rudolphii (Rudolphi, 1819), a common parasite of the proventriculus of cormorants, was experimentally studied. Within the eggs cultivated in freshwater under laboratory temperatures of 20-22 °C, the developing larva undergoes two moults on days 4-5, attaining the third larval stage. Most of the ensheathed third-stage larvae, 291-457 µm long, hatch spontaneously from egg shells on days 5-6. Experiments have indicated that hatched ensheated third-stage larvae and those still inside egg capsules are already infective to copepods and fishes, which both can be considered paratenic (metaparatenic) hosts. Five copepod species, Acanthocyclops vernalis, Cyclops strenuus, Ectocyclops phaleratus, Eucyclops serrulatus and Megacyclops viridis, the isopod Asellus aquaticus and small carps Cyprinus carpio were infected by feeding them these larvae. In addition, 9 fish species, Alburnoides bipunctatus, Anguilla anguilla, Barbatula barbatula, Cyprinus carpio, Gobio gobio, Perca fluviatilis, Phoxinus phoxinus, Poecilia reticulata and Tinca tinca, were successfully infected by feeding them copepods previously infected with C. rudolphii third-stage larvae. In fishes, larvae from copepods penetrate through the intestinal wall to the body cavity, where, in a few weeks, they become encapsulated; the larvae substantially grow in fish, attaining the body length up to 4.87 mm. In carp fry, the nematode third-stage larvae survived for about 15 months (up to 18 months in fish infected directly, i.e., without copepods). One small cormorant (Phalacrocorax carbo sinensis) was successfully infected by feeding it with copepods harbouring C. rudolphii third-stage larvae.