Parthenogenetic generations of Helicometra fasciata Rud., 1819 (Trematoda: Opecoelidae) in the Black Sea molluscs Gibbula adriatica

Morphology of the Helicometra fasciata Rud., 1819 parthenogenetic generation from the Black Sea gastropods Gibbula adriatica (Phil.) was studied for the first time. Data on seasonal dynamics of the hemipopulation of daughter sporocysts are given. Daughter sporocysts of H. fasciata infest 10 +/- 0.2 % of G. adriatica (mainly specimens of larger size and elder age classes). As a rule, local microhemipopulations of daughter sporocysts castrate mollusc hosts. Reproduction of H. fasciata daughter sporocysts is asynchronous: daughter sporocysts born specimens of next sporocyst generation during autumn and winter, and then they begin producing cercaria. In winter development of the cercaria embryo is blocked. Second change of the character of the each sporocyst' posterity is impossible because of the annual life cycle of G. adriatica. Endogenous agglomeration of the H. fasciata daughter sporocysts is extremely little: individuals of next sporocyst generation develop from no more than 2 % of embryonic balls. Energy resources of the mollusc host are used by the H. fasciata daughter sporocysts mainly for producing cercaria; this fact can be interpreted as an adaptation of H. fasciata to using medium-sized, short-living mollusc hosts.     

Description of Acanthotrema armata n. sp. (Trematoda: Heterophyidae) from Larus audouinii (Aves: Laridae), with an amended diagnosis of the genus Acanthotrema Travassos, 1928

Acanthotrema armata n. sp. (Trematoda: Heterophyidae) is described from the gut of Larus audouinii Payraudeau (Aves: Laridae) caught on the Chafarinas Islands in the southwestern Mediterranean (Spain). This trematode differs from other species of Acanthotrema Travassos, 1928 in having two spined, sclerotised pieces in the ventrogenital sac and in the position of the genital pore. Parastictodora Martin, 1950 is considered a synonym of Acanthotrema. As the diagnosis of the genus Acanthotrema was based only on its type-species, it is amended to include the characteristics of the new species and those attributed to Parastictodora.     

Study of fecundity of Bunodera luciopercae (Trematoda: Bunoderidae)

The seasonal dynamics of the maturation of trematode Bunodera luciopercae was investigated in 1992-1998. The actual fecundity of adult helminths from the ruff, perch, sander and volga pike-perch in the Rybinsk Reservoir was registered in the end of spring. The accumulation process of eggs reflected the host alteration and depended on the food ration, body length and sex of hosts.     

Egg and miracidium of Hirudinella ventricosa (Trematoda: Hirudinellidae)

It is reported for the first time that Hirudinella ventricosa releases eggs in strings, each string containing active spermatozoa and numerous oval, thick-shelled, translucent eggs measuring 40-42 x 28-30 microns. Each egg contained a fully developed miracidium with an anterior crown of spines.     

Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda)

Complete small subunit ribosomal RNA gene (ssrDNA) and partial (D1-D3) large subunit ribosomal RNA gene (lsrDNA) sequences were used to estimate the phylogeny of the Digenea via maximum parsimony and Bayesian inference. Here we contribute 80 new ssrDNA and 124 new lsrDNA sequences. Fully complementary data sets of the two genes were assembled from newly generated and previously published sequences and comprised 163 digenean taxa representing 77 nominal families and seven aspidogastrean outgroup taxa representing three families. Analyses were conducted on the genes independently as well as combined and separate analyses including only the higher plagiorchiidan taxa were performed using a reduced-taxon alignment including additional characters that could not be otherwise unambiguously aligned. The combined data analyses yielded the most strongly supported results and differences between the two methods of analysis were primarily in their degree of resolution. The Bayesian analysis including all taxa and characters, and incorporating a model of nucleotide substitution (general-time-reversible with among-site rate heterogeneity), was considered the best estimate of the phylogeny and was used to evaluate their classification and evolution. In broad terms, the Digenea forms a dichotomy that is split between a lineage leading to the Brachylaimoidea, Diplostomoidea and Schistosomatoidea (collectively the Diplostomida nomen novum (nom. nov.)) and the remainder of the Digenea (the Plagiorchiida), in which the Bivesiculata nom. nov. and Transversotremata nom. nov. form the two most basal lineages, followed by the Hemiurata. The remainder of the Plagiorchiida forms a large number of independent lineages leading to the crown clade Xiphidiata nom. nov. that comprises the Allocreadioidea, Gorgoderoidea, Microphalloidea and Plagiorchioidea, which are united by the presence of a penetrating stylet in their cercariae. Although a majority of families and to a lesser degree, superfamilies are supported as currently defined, the traditional divisions of the Echinostomida, Plagiorchiida and Strigeida were found to comprise non-natural assemblages. Therefore, the membership of established higher taxa are emended, new taxa erected and a revised, phylogenetically based classification proposed and discussed in light of ontogeny, morphology and taxonomic history.     

Life cycle of Coitocoecum plagiorchis (Trematoda: Digenea: Opecoelidae)

The life cycle of Coitocoecum plagiorchis Ozaki, 1926 (Coitocaecum is an incorrect subsequent spelling) was studied in the field and laboratory. The study was conducted at the Futatsu River and the Chikugo River, Kyushu, Japan. Adults of C. plagiorchis were obtained from fishes Coreoperca kawamebari, Rhinogobius spp. and Odontobutis obscura. Cotylomicrocercous cercariae with a two-point stylet (= Cercaria distyloides Faust, 1924) were detected in pleurocerid snails (Semisulcospira spp.). Metacercariae with a cyclocoel were obtained from shrimp (Neocaridina denticulata). The cercariae were experimentally exposed to the shrimp, and subsequently metacercariae with a cyclocoel were recovered from the shrimp within 24 days after exposure. These metacercariae were identified as C. plagiorchis. The sporocysts, cercariae, metacercariae and adults are briefly described.     

The miracidium microanatomy of Philophthalmus rhionica (Trematoda: Philophthalmidae)

The study of ultrastructure of Philophthalmus rhionica miracidium was carried out. Update the ultrastructures of miracidium were studied in a restricted number of species belonging to the families Notocotylidae, Paramphistomatidae, Sanguinicolidae, Fasciolidae, Schistosomatidae (Galaktionov, Dobrovolsky, 1998). The ultrastructure of representatives of two latter families, Fasciola hepatica and Schistosoma mansoni respectively, have been examined most carefully. The family Philophthalmidae differs from the families Fasciolidae and Schistosomatidae by the aberrant pedogenetic miracidium.