Summary :A survey of cercariae and metacercariae (Trematoda, Digenea) from the great pond snail (Lymnaea stagnalis) in Central Europe (Austria, Czech Republic, South-East Germany, Poland and Slovak Republic) is presented, based on a study of 3,628 snails examined from 1998 to 2005. A total of 953 (26.3 %) L. stagnalis were infected with 24 trematode species comprising 19 species of cercariae and 11 species of metacercariae (six species occurred both as cercarie and metacercarie) of eight families. The dominant cercariae were those of Opisthioglyphe ranae (159 hosts infected), Plagiorchis elegans (141) (both family Plagiorchiidae) and Echinoparyphium aconiatum (153) (Echinostomatidae); 14 double infections were found. The most frequent metacercariae were those of Neoglyphe locellus (71) (Omphalometridae), E. aconiatum (66), Echinostoma sp. (59) and Moliniella anceps (48) (Echinostomatidae). In the previous studies carried out in Central Europe, a very similar spectrum of nine trematode families of 22 cercariae determined to species level and 43 types of cercariae reported under generic or provisional names, which can be in many cases conspecific with the previous taxa, were found. A simple key to identification of cercariae and metacercariae, together with their illustrations, is provided. Résumé

A survey of the larval stages (cercariae and metacercariae) of trematodes (Digenea) found in planorbid snails in Central Europe (Austria, Czech Republic, south-east Germany, Hungary, Poland and the Slovak Republic) is presented based on a study of 7,628 snails of 12 species examined between 1998-2006. A total of 34 trematode larval stages, comprising cercariae of 28 species and metacercariae of seven species (one species occurred both as cercaria and metacercaria) of nine families were found in 898 (11.5%) snails of eight species. The dominant cercariae were those belonging to the Rubenstrema exasperatum (Rudolphi, 1819)/Neoglyphe locellus (Kossack, 1910) species complex, Tylodelphys excavata (Rudolphi, 1803) and Echinostoma spiniferum (La Valette, 1855) sensu Nasincová (1992), all from Planorbarius corneus (Linnaeus). Almost the same spectrum of cercariae of the families Echinostomatidae, Plagiorchiidae and Omphalometridae was found in the present study as in previous reports; however, a considerably lower spectrum of cercariae of the families Diplostomidae and Strigeidae was recorded. The most frequent metacercariae were those of Echinoparyphium aconiatum Dietz, 1909, Neoglyphe locellus and Moliniella anceps (Molin, 1859), all occurring mainly in P. corneus. The most heavily infected snail species was P. corneus, followed by Planorbis planorbis (Linnaeus) and Segmentina nitida (Müller). The widest spectrum of trematode species was found in P. planorbis and P. corneus. Forty-two cercariae identified to the species level belonging to 15 families, plus an additional 43 taxa recorded under generic or provisional names, were reported from 11 species of planorbids in previous studies carried out in Central Europe. However, the actual number of trematode species occurring in the planorbid snails is probably much lower, because many, if not most, larval stages reported under provisional names or unidentified to the species level may be conspecific with identified adult forms. A key to the cercariae and metacercariae recorded from planorbids in Central Europe, together with illustrations of those species encountered most frequently in the field, is provided to facilitate identification.

The cercariae of five flukes, which are potential human para sites, Opisthorchis viverrini (family Opisthorchiidae), Haplorchis taichui (Heterophyidae), Schistosoma spindale (Schistosomatidae), Fasciolopsis buski, and Fasciola gigantica (Fasciolidae) were found in freshwater snails from Laos. The cercariae of the above species, recorded in Laos for the first time, are illustrated and their morphology is briefly described. The snail Helicorbis umbi licalis represents a new intermediate host of F. buski. The occur rence of medically important snails in the Vientiane province will also be discussed.

A study on the life cycle of the trematode Asymphylodora tincae (Modeer 1790) (family Monorchiidae), carried out under both natural and laboratory conditions, revealed as its most remarkable characteristics the absence of a metacercarial stage. The definitive host, the tench [Tinca tinca (L.)], became directly infected after the ingestion of snails harbouring rediae with mature cercariae. With the exception of the sporocyst, all developmental stages from both naturally and experimentally infected pulmonate snails as well as adults from experimental fish hosts were described and illustrated, including the surface morphology of the cercariae, studied by scanning electron microscopy. Confusion in the identification of larval stages from pulmonate snails and the prosobranchiate genus Bithynia, hitherto identified as A. tincae by other authors, are briefly discussed with regard to the present results.

Two echinostome trematodes of the genus Petasiger, P. exaeretus Dietz, 1909 and P. phalacrocoracis (Yamaguti, 1939), parasitising cormorants (Phalacrocoracidae), were found in Phalacrocorax carbo L. from the Czech Republic. Both taxa are redescribed and literary data on their occurence in cormorants are reviewed. The species P. exaeretus appears to be a rather rare species, hitherto recorded in Phalacrocorax carbo in Europe, Kirghizia and Azerbaidzhan. P. baschkirovi Ablassov & Iksanov, 1959 is synonymized with P. exaeretus. P. phalacrocoracis (syn. P. hospitale (Mendheim, 1940) and P. exaeretus auct. nec Dietz, 1909), which has previously been misidentified and erroneously designated as P. exaeretus, appears to be the commonest species of the genus, parasitising cormorants in the Palaearctic Region (Europe, CIS [USSR], Japan) and in Australia. Differential diagnoses of both the above mentioned species are presented.

A revision of the literary data showed that the name Trichosoma carbonis Rudolphi, 1819 has to be considered a nomen nudum, which is invalid and unavailable according to the International Code of Zoological Nomenclature. The first recognisable description of the nematode designated Capillaria carbonis (Rudolphi) is that by Dubinin & Dubinina (1940) and, consequently, the correct valid name of this species is Baruscapillaria carbonis (Dubinin & Dubinina, 1940) n. comb. However, due to its inadequate description, it should be considered a species inquirenda. It is highly probable that the records of "Capillaria carbonis" by subsequent authors related, in fact, to more than one species. The nematodes recently collected from the small intestine of the common cormorant Phalacrocorax carbo (L.) from southern Moravia, Czech Republic, differ considerably from Baruscapillaria carbonis mainly in the structure of the male caudal end and are considered to represent a new species, B. rudolphii n. sp. This is characterised mainly by the length of spicule (1.25 mm), presence of a non-spiny spicular sheath, structure of the male caudal end, absence of a vulvar appendage in female and by various body and organ measurements. Since Trichosoma corvorum Rudolphi, 1819 is also a nomen nudum, the valid name of the intestinal capillariid which parasitises mainly birds of the genus Corvus in the Palaearctic region is Baruscapillaria resectum (Dujardin, 1845) n. comb. (syn. Trichosomum resectum Dujardin, 1845).

Light microscopy observations on armature and chaetotaxy of armature and outer structure of sensory cells. They show a variety Diplostomum paracaudum (I les, 1959) were veryfied in scanning in cilia length and structure of a collar. The specific distribution electron microscopy. The new findings concern some details of of particular sensilla forms is observed. Résumé : Vérification au microscope électronique à balayage de l'armature et de la chétotaxie de la cercaire de Diplostomum paracaudum (Iles, 1959) (Digenea, Diplostomidae). Nous avons vérifié au microscope électronique à balayage (MES) les observations précédentes sur l'armature et sur la chétotaxie de la cercaire de Diplostomum paracaudum (Iles, 1959). Les nou velles observations concernant certains détails sur les épines et sur la structure externe des cellules sensorielles. Mise en évidence de différences dans la longueur des cils et dans la structure du col lier. La distribution spécifique des différents types de papilles est étudiée.

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