Abnormalities in adult digeneans, with special reference to Phyllodistomum umblae(Fabricius) (Platyhelminthes, Gorgoderidae)

During examination of a large sample of Phyllodistomum umblae from Arctic char, Salvelinus alpinus , in Lake Tokke (Drangedal, type locality) and Lake Katnosa (Nordmarka, vicinity of Oslo), Norway, several abnormalities were found in the adult specimens. The paper describes the abnormal cases recovered and gives a systematized review of abnormal digeneans reported in the literature. Different terms used in digenean teratology and morphology are also discussed and defined. Abnormal cases occur in P. umblae with regard to the dimensions of specific structures (caeca, ovary, oötype, seminal vesicle, testes, uterus, vitellarium) and in the numbers of ovaries and testes. Polymorphism in testes position was observed and obstructions of the reproductive organs were evident. The size variability of the seminal vesicle and ovary and variable appearance of the vitelline bodies are demonstrated.     

A Redescription of Adult Phyllodistomum umblae (Fabricius) (Digenea, Gorgoderidae) from Salvelinus alpinus (L.) in Norway

Phyllodistomum umblae (Fabricius, 1780), originally described on the basis of specimens recovered from the ureter of Arctic char Salvelinus alpinus in Drangedalen, Norway, is here redescribed with both light (LM) and scanning electron microscope (SEM) from material obtained from the type host and type locality. This species has been overlooked in general text-books of this century, e.g. those of Dawes and Yamaguti, but was discussed by Nybelin in a paper in 1926 in which he suggested its conspecificity with P. conostomum Olsson. The dimensions, shapes, position and arrangement of the internal structures and selected size ratios are described and illustrated with LM-pictures. The SEM-investigation reveals the tegumental microstructure, and special emphasis is given to the arrangement of papillae. The body papillae comprise: (a) constant numbers in a constant bilateral arrangement; (b) a variable number in an orientated bilateral concentration called rows; (c) regional concentrations; (d) randomly distributed ones. This system and its variability are described and figured. Four types of papillae, and their distribution as seen by SEM, are described. These results are compared with the results from other SEM–investigations on gorgoderids.     

Characteristics of karyotype structure in Phyllodistomum umblae (Trematoda: Gorgoderidae) from Lake Baikal

Haploid complement of Phyllodistomumn umblae ex baikal whitefish from Lake Baikal consists of 8 chromosomes (6 metacentrics and 2 submetacentrics). The significant difference is observed in the ratio of acrocentrics and metacentrics in the haploid set of chromosomes between isolated populations of P. umblae from Baikal region and from Chukotka. The hypothesis is advanced that these chromosome populations may be chromosome races of P. umblae.     

The distribution of Phyllodistomum umblae and Phyllodistomum folium (Trematoda: Gorgoderidae) in the excretory system of fishes

It is shown, that the distribution of Phyllodistomum umblae in the excretory system of all investigated species of salmonids has a principal similarity. The distribution of P. umblae in the excretory system of the Siberian dace and the Siberian roach is distinguished from that of P. folium.     

Molecular prospecting for cryptic species in Phyllodistomum lacustri (Platyhelminthes,Gorgoderidae)

Rosas‐Valdez, R., Choudhury, A. & Pérez‐Ponce de León, G. (2011). Molecular prospecting for cryptic species in Phyllodistomum lacustri (Platyhelminthes, Gorgoderidae). —Zoologica Scripta, 40, 296–305. Partial sequences of the 28S ribosomal RNA and cytochrome c oxidase I (COI) genes were compared among populations of a widely distributed and morphologically uniform digenean species in North America, Phyllodistomum lacustri, a parasite characteristically associated with ictalurid catfishes. Specimens were collected from the urinary bladder of ictalurid hosts in six localities of North America, spanning most of the latitudinal range of this freshwater fish group. Sequences of other congeneric species, including a potentially close relative, P. staffordi, were also obtained and used for comparison. Analyses of both molecular markers show very low or no intrapopulation variation within each sampling site. However, samples of P. lacustri from different hosts and regions exhibit varying levels of interpopulation genetic differences. Such differences are explained by the wide geographical distribution and host range of the ictalurids they parasitize, particularly in ictalurids distributed in Mexican freshwaters where they experienced a diversification process. Variation in both nuclear and mitochondrial genes and phylogenetic analyses, in conjunction with geographical and host information (drainage isolation and endemicity of the host species), indicate that at least three populations show potential as cryptic species.     

The morphological variability of the maritae of Phyllodistomum umblae and Phyllodistomum folium (Trematoda: Gorgoderidae) from fish in the Lake Baikal basin

The host variability of adults of Phyllodistomum umblae and P. folium in fishes of the Baikal region has been studied. The absence of considerable geographical variability of P. umblae in Coregonus lavaretus (Lake Baikal, Lake Storsj?n in Sweden) has been shown. The complexes of most stable (the size of acetabulum and eggs, location of acetabulum, ovary and vitelline bodies) and variable (the distance from oral sucker to intestinal bifurcation, distance from intestinal back edge to body end, width of seminal vesicle) features of trematodes of the genus Phyllodistomum have been determined.     

Evidence of complement-mediated killing of Discocotyle sagittata (Platyhelminthes, Monogenea) oncomiracidia

Discocotyle sagittata oncomiracidia were rapidly killed when incubated in na?ve plasma and immune sera from both rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta), the killing proceeding at a faster rate with blood material from the latter fish species. The lethal activity of na?ve plasma and immune sera was comparable. This was abolished after incubation at 45 degrees C for 30 min and by the addition of EDTA but not EGTA supplemented with Mg(2+), indicating that complement acting via the alternative pathway is responsible for the parasiticidal effect observed. Scanning electron micrographs showed varying degrees of surface disruption in larvae exposed to fish plasma, suggesting that complement acts by breaching the oncomiracidial tegument. Control (untreated) oncomiracidia showed no damage. Ultrastructural damage was more extensive in oncomiracidia exposed to brown trout plasma than to rainbow trout plasma for equal periods, suggesting that the complement cascade may be involved in mediating host susceptibility.     

The importance of the fixation of colour,pattern and form in tropical Pseudocerotidae (Platyhelminthes,Polycladida)

At last a fixation method that ensures tropical pseudocerotid polyclads are fixed flat, preserved for histological preparation and which also retains their colour pattern has been developed. FCA-PGPP (Formaldehyde Calcium Acetate-Propylene Glycol, Propylene Phenoxetol) fixative is frozen and worms are coaxed onto filter paper which is then laid on the frozen fixative. As a consequence, over 230 species have been documented from the southern Great Barrier Reef and eastern Papua New Guinea (Newman & Cannon, 1994; in press). It was determined that species diagnoses need to be based on colour pattern, general morphology of living animals and serial reconstructions of the male anatomy.Christensen Research Institute Contribution No. 82     

Ultrastructural observations on the sensory papillae of juvenile and adult Gorgoderina vitelliloba (Trematoda: Gorgoderidae)

Hoole D. and Mitchell J.B. 1981. Ultrastructural observations on the sensory papillae of juvenile and adult Gorgoderina vitelliloba (Trematoda : Gorgoderidae). International Journal for Parasitology11: 411–417. Ultrastructural observations have been made on the juvenile and adult stages of Gorgoderina vitelliloba from Rana temporaria. Four types of sensory papillae occur; button, rosette, ciliated and domed. Button papillae, which contain a ciliary-rootlet but lack a cilium, occur on the oral sucker, dorsal preacetabular surface and the lateral margins of the fluke. Scanning electron microscopical observations reveal that the tegumental protuberances of the papilla are transformed from a spiked or conical appearance in juvenile flukes to a rounded form in adult flukes. Rosette papillae, which also contain a rootlet, occur on the lip of the ventral sucker of both juvenile and adult flukes. Ciliated papillae only occur on the oral sucker of juvenile flukes. Domed papillae, which contain a large area of electron-dense material, occur on the internal surface of the ventral sucker of both juvenile and adult flukes. The functions of papillae and their possible role in the migration of the parasite are discussed.     

A method for the preparation of high-molecular-weight DNA from marine and freshwater triclads (Platyhelminthes, Turbellaria)

Although the last decade has seen much activity devoted to the phylogeny of the Platyhelminthes, such activity has relied in the main on traditional anatomical, ultrastructural, and developmental data. Extension of these studies to the molecular level has been impeded by the lack of a reliable method for the isolation of DNA from these organisms, especially marine triclads whose DNA is particularly difficult to isolate using methods currently used with other eukaryotic or prokaryotic organisms. We report here the details of a method that results in the rapid isolation of relatively pure DNA in good yields from small amounts of material. The method involves the treatment of the animals with high concentrations of NaDodSO4 followed by phenol extraction, resulting in a product that is an excellent substrate for restriction endonuclease digestion and Southern blotting.     

Effects of preparation and fixation on three quantitative fluorescent cytochemical procedures

Summary A series of experiments was undertaken in which cells dissociated from the abdominal lymph nodes of mice were lightly centrifuged into slides and fixed either wet or after drying in 70% ethanol, 1% glutaraldehyde, 1% formaldehyde, or neutral formalin. Three fluorescent cytochemical methods were evaluated: staining of DNA with mithramycin; fluorochroming of basic groups of proteins with brilliant sulfaflavine (BSF); and staining of sulfhydryl and disulfide groups with N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM). In the case of mithramycin, the best results were obtained after fixation in 70% ethanol without drying. Staining of dried preparations fixed in 1% glutaraldehyde also yielded reasonably consistent results, although the fluorescence was lower, and the variability higher, than in the group fixed without drying in 70% ethanol. The use of fixatives containing formaldehyde resulted in fluorescence values of only about onethird those of the other two groups, and the variability of the data was higher. In material stained with BSF, satisfactory results were obtained in preparations fixed without drying in neutral formalin containing mersalyl acid. Other fixatives could be used, but the resulting coefficients of variation were higher than those of formalin-fixed material. Sulfhydryl to disulfide ratios approaching those expected from biochemical evidence were obtained in DACM-stained material only after fixation without drying in neutral formalin containing mersalyl acid. Inverted sulfhydryl-disulfide ratios were observed in material fixed without drying in 70% ethanol; and in dried metarial fixed in 1% formaldehyde, neutral formalin, or 1% glutaraldehyde.     

Effects of preparation and fixation on three quantitative fluorescent cytochemical procedures

A series of experiments was undertaken in which cells dissociated from the abdominal lymph nodes of mice were lightly centrifuged into slides and fixed either wet or after drying in 70% ethanol, 1% glutaraldehyde, 1% formaldehyde, or neutral formalin. Three fluorescent cytochemical methods were evaluated: staining of DNA with mithramycin; fluorochroming of basic groups of proteins with brilliant sulfaflavine (BSF); and staining of sulfhydryl and disulfide groups with N-(7-dimethylamino-4-methylcoumarinyl)maleimide (DACM). In the case of mithramycin, the best results were obtained after fixation in 70% ethanol without drying. Staining of dried preparations fixed in 1% glutaraldehyde also yielded reasonably consistent results, although the fluorescence was lower, and the variability higher, than in the group fixed without drying in 70% ethanol. The use of fixatives containing formaldehyde resulted in fluorescence values of only about one-third those of the other two groups, and the variability of the data was higher. In material stained with BSF, satisfactory results were obtained in preparations fixed without drying in neutral formalin containing mersalyl acid. Other fixatives could be used, but the resulting coefficients of variation were higher than those of formalin-fixed material. Sulfhydryl to disulfide ratios approaching those expected from biochemical evidence were obtained in DACM-stained material only after fixation without drying in neutral formalin containing mersalyl acid. Inverted sulfhydryl-disulfide ratios were observed in material fixed without drying in 70% ethanol; and in dried material fixed in 1% formaldehyde, neutral formalin, or 1% glutaraldehyde.     

The microtopography and papillar arrangement on adult Gorgoderina vitelliloba (Olsson) (Digenea, Gorgoderidae) from amphibians in relation to fish gorgoderids

Specimens of Gorgoderina vitelliloba recovered from Rana temporaria and R. pipiens purchased in Eire are described using SEM. The microtopography is illustrated with particular emphasis on the type, number and arrangement of papillae. Significant differences in papillar arrangement were observed between the present specimens of G. vitelliloba from amphibians and that described earlier for the type species of Phyllodistomum from pike, Esox lucius , and Phyllodistomum from salmonids. The differences in papillae number and arrangement on the ventral sucker of G. vitelliloba and the Phyllodistomum species are interpreted as confirmation of their generic separation. The papillae types found are illustrated by SEM and discussed.     

Biological studies on adult water snipe fly,Atherix ibis (Fabricius, 1798) (Diptera: Athericidae): old myths and new facts

The water snipe fly, Atherix ibis, is known for its eggbearing females aggregating in clusters. They are most frequently found as flat crusts under the outer parts of bridge ceilings above the water. There is no persistent pattern in the cluster distribution either in relation to the current direction or to the sun. Females aggregate in early summer in short periods of warm and calm weather only. Females are attracted to an aggregation site, probably by pheromones. The flies fasten to the surface and to each other by minute Velcro-like structures on their feet. The eggs are shed inside the cluster. After 9–12 days the eggs hatch, and the larvae leave clusters and drop into the water. There is no increased temperature inside the cluster. There are no signs of larval feeding on either dead flies or siblings in the cluster. The majority of larvae leave the cluster during night time, also when the normal day–night rhythm is eliminated by experimental black-out.     

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.     

Hox genes from the Polystomatidae (Platyhelminthes, Monogenea)

Hox genes form a multigenic family that play a fundamental role during the early stages of development. They are organised in a single cluster and share a 60 amino acid conserved sequence that corresponds to the DNA binding domain, i.e. the homeodomain. Sequence conservation in this region has allowed investigators to explore Hox diversity in the metazoan lineages. Within parasitic flatworms only homeobox sequences of parasite species from the Cestoda and Digenea have been reported. In the present study we surveyed species of the Polyopisthocotylea (Monogenea) in order to clarify Hox identification and diversification processes in the neodermatan lineage. From cloning of degenerative PCR products of the central region of the homeobox, we report one ParaHox and 25 new Hox sequences from 10 species of the Polystomatidae and one species of the Diclidophoridae, which extend Hox gene diversity from 46 to 72 within Neodermata. Hox sequences from the Polyopisthocotylea were annotated and classified from sequence alignments and Bayesian inferences of 178 Hox, ParaHox and related gene families recovered from all available parasitic platyhelminths and other bilaterian taxa. Our results are discussed in the light of the recent Hox evolutionary schemes. They may provide new perspectives to study the transition from turbellarians to parasitic flatworms with complex life-cycles and outline the first steps for evolutionary developmental biological approaches within platyhelminth parasites.     

Ultrastructure of the vitelline follicles of Gorgoderina vitelliloba (Trematoda: Gorgoderidae)

An electron microscope study of the vitelline follicles of Gorgoderina vitelliloba indicates that they contain vitelline cells in various stages of development. Juvenile cells are small and characterised by a little cytoplasm. During differentiation a large amount of granular endoplasmic reticulum develops. In more mature cells, indistinct Golgi complexes give rise to globules of shell protein which migrate to form clusters at the periphery of the cell. Further maturation results in the appearance of large lipid bodies in the vitelline cell cytoplasm.Developing vitelline cells are ensheathed by nurse cell cytoplasm containing numerous small vacuoles which appear to be derived from smooth endoplasmic reticulum. It is suggested that nurse cells may have a role in selection and transport of nutrient material for vitelline cells and that they manufacture precursors of lipid which is subsequently stored as a food reserve in mature vitelline cells. Possible transport sites between parenchymal cells and nurse cells were identified.     

Ultrastructure of the pharynx of Prorhynchus (Platyhelminthes, Lecithoepitheliata)

The pharynx variabilis of Prorhynchus is strongly muscular, with a small pharyngeal fold and a thin surrounding sheath. There is one row of inner longitudinal musclcs, up to six rows of inner circular muscles, many radial muscles, one row of outer circular and one row of outer longitudinal muscles, with no sphincter muscle groups. Three kinds of secretion, produced in a cluster of gland cell bodies posterior to the pharynx, enter the pharynx wall. They travel anteriorly in ducts and two kinds unite in a common duct just prior to discharging into the anterior region of the pharynx lumen. The perikarya of lumen epithelial cells lie within the pharynx musculature and, at the anterior and posterior margins of the pharynx, external to the pharynx. Bundles of ciliated receptors are numerous at the anterior and posterior constrictions. Similarities in the ultrastructure of flame bulbs of Rhabdocoela and Lecithoepitheliata suggest a relationship between these groups. However, the usefulness of pharynx ultrastructure for platyhelminth phylogeny cannot be assessed until complete ultrastructural studies of various groups of Rhabdocoela have been made.