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Although numerous genetically isolated entities within Contracaecum rudolphii sensu lato are presently defined, information on the distribution and ecology of these groups is nonetheless in demand. In the present study, information based upon DNA sequence data (restriction analysis and sequencing of rDNA) on the distribution of the species C. rudolphii A and C. rudolphii B in the cormorant Phalacrocorax carbo sinensis from the Baltic region (Poland and Finland) is provided. These data corroborate previous work that identified C. rudolphii A in brackish water regions and C. rudolphii B in fresh water sites, although mixed infections also occur. The 2 species may inhabit the same host specimen. One rare heterozygote of the species was recorded.

The structure of the pharynx of the adult female nematode Anguillicoloides crassus (Spirurina) has been studied for the first time using light and transmission electron microscopy. The cylindrical pharynx consists of a short anterior muscular corpus and an enlarged posterior glandular and muscular postcorpus. The main cellular components of the pharynx of A. crassus include the muscle cells, the marginal cells, the nerve cells, and 1 dorsal and 2 subventral glands. New observations for nematodes include: (1) the non-contractile regions of pharyngeal musculature in the corpus have specific appearance; (2) the ventrosublateral longitudinal nerve in the pharynx has an enlarged, enucleated anterior part, with a pronounced palmate projections; and (3) abundant lysosomelike membranous bodies consisting of myelinlike figures of varied size present in marginal cells and pharyngointestinal valve. The 2 subventral glands and, apparently, the single dorsal gland, have their openings at the same level, i.e., at the border between the corpus and postcorpus. The pharyngeal-intestinal valve joins the pharynx to the intestine. Knowledge of the ultrastructure of these complex characters may be useful in understanding of functional features, and for comparative morphology as well as evolutionary considerations within the Chromadorea.

Contracaecum sp. larvae (L3) from fish were identified using nucleotide sequences of the internal transcribed spacers ITS-1 and ITS-2 of the ribosomal DNA. The nematode larvae originated from fish in a freshwater situation (crucian carp Carassius carassius, from Selment Wielki Lake in Mazury, northeastern Poland) and a brackish-water region (Caspian round goby Neogobius melanostomus from the Baltic Sea, Gdafisk Bay at the Polish coast). Two strains (Contracaecum rudolphii A and B) of Contracaecum rudolphii senso lato, a parasite common at the adult stage in fish-eating birds, were identified. In fish from the freshwater site, only the strain temporarily designated C. rudolphii B was identified; in the brackish-water region, both strains were found, suggesting that fish serve as paratenic host for both genotypes. Contracaecum rudolphii sensu lato has been recorded in several species of fish-eating birds in Poland, particularly in the great cormorant, Phalacrocorax carbo, in which the abundance is highest. The results, although based on a restricted number of larvae, suggest that the life cycles of both genotypes can be completed in the Polish region and that at least one of them, C. rudolphii B, can develop both in fresh and brackish water.

The spatial relationship between the musculature and the NADPH-diaphorase (NADPH-d) activity, 5-HT and FMRFamide immunoreactivities in redia, cercaria and adult Echinoparyphium aconiatum was studied using scanning electron microscopy (SEM), NADPH-d histochemistry, immunocytochemistry, and confocal scanning laser microscopy (CSLM). TRITC-conjugated phalloidin was used to stain the musculature. Staining for NADPH-d was observed in the central (CNS) and peripheral nervous system (PNS) of all three stages. NADPH-d positive nerves occurred very close to muscle fibres. 5-HT-immunoreactive (5-HT-IR) nerve cells and fibres occurred in the CNS and PNS and close to muscle fibres. FMRFamide-IR nerve fibres were observed in the CNS and PNS of adult worms. This is the first time, the presence of the NADPH-d has been demonstrated in the larval as well as the adult stages of a fluke.

The somatic cuticle of adult female Philometra obturans (Prenant, 1886) (Nematoda: Dracunculoidea) consists of five zones and an overlying prominent fuzzy epicuticle, closely adherent to the gill arterial wall of the host. The cuticle is fenestrated and infiltrated with electron-dense substances. It protrudes into the hypodermis in the form of numerous protuberances. The plasma membrane of the hypodermis forms prominent infoldings within the subcuticular region. Numerous endosomes bud off from the cuticle into the hypodermis. Glycogen deposits are present within the hypodermis and muscle cells. The muscle cells are well developed, polymyarian in number (up to 30 in each quadrant) and coelomyarian in shape. The body wall of adult female P. obturans reveals several ultrastructural features which are common to the members of Filarioidea.

Here, for the first time in an ascaridoid (Hysterothylacium auctum), we present structural features of the phasmids, paired sense organs, positioned in a bilateral manner close to the point of the tail; the features were obtained using scanning and transmission electron microscopy. We found that each phasmid consists of a single ciliated dendritic process situated in a phasmidial canal surrounded by 2 supporting cells, a socket and a sheath cell. The socket cell contains clusters of electron-dense fibrous material in its apical region and covers the phasmidial canal along its whole length. The sheath cell is characterized by a well-developed endoplasmic reticulum. The phasmidial canal is lined with a thin layer of cuticle that becomes incomplete at the base of the ciliated dendritic process. In this region, the dendritic process consists primarily of a high number of microtubule singlets and some peripheral microtubule doublets. The base of the dendritic process, containing numerous striated rootlets, gives off a large number of fingerlike offshoots, villi, invading the surrounding sheath cell. The systematic significance and functional implication of the phasmid in nematodes are also discussed.

The fine structure of the mature spermatozoon of the pseudophyllidean tapeworm Eubothrium crassum, a parasite of salmonid fishes, has been studied by transmission electron microscopy for the first time. The mature spermatozoon of E. crassum is filiform and tapered at both extremities. It contains two axonemes of unequal length showing the 9 + "1" pattern of Trepaxonemata. The anterior extremity exhibits a crested body 50-100 nm thick. It spirals around the outside of the anterior region of the spermatozoon. The nucleus is electron-dense, exhibiting a fibrous appearance in its middle (the broadest) region. The cortical microtubules are of two types and are situated parallel to the spermatozoon axis. The cytoplasm is slightly electron-dense and contains numerous electron-dense granules in region II of the spermatozoon. A ring of electron-dense, centred microtubules surrounds the axoneme, together with the underlying ring of moderately electron-dense, subjacent submicrotubular material in region V. The anterior and posterior extremities of the spermatozoon lack cortical microtubules and contain a single axoneme. Our results reveal several peculiarities, in which the spermatozoon of E. crassum differs from those of other pseudophyllidean cestodes.

Spermiogenesis of the pseudophyllidean tapeworm Eubothrium crassum has been described by the aid of transmission electron microscopy for the first time. Initially, early spermatids form a distal cytoplasmic protrusion, a differentiation zone containing a small electron-dense, apically oriented region. Out of this region, two centrioles with rootlets develop. The centrioles become orientated in the same plane with the appearance of an intercentriolar body. Now, the long axes of the rootlets are parallel with each other and with the long axis of the nucleus. Two flagella of subsequently unequal length are formed very rapidly. Simultaneously, a median cytoplasmic process (MCP) develops distal to the flagella. Two arching membranes appear at the base of the differentiation zone. Each flagellum, still being in contact with an intercentriolar body, rotates to a position parallel with the MCP. The nucleus migrates very rapidly into the MCP at this stage. Subsequently, the two flagella fuse with the MCP. Finally, the basal bodies with the rootlets detach from the flagella, the intercentriolar body changes its structure and spermatids are pinched off from a condensing residual cytoplasm at the level of the arching membranes.

Nuclear-encoded large-subunit ribosomal DNA sequences were used to infer a phylogenetic hypothesis for 17 taxa (16 nominal species) of the genera Contracaecum and Phocascaris. Phylogenetic trees based on these data have been used to assess the validity of the taxonomic distinction between these genera, which was based on the presence or absence of certain structural features, rather than on explicit hypotheses of evolutionary history. Phylogenetic hypotheses based on parsimony, likelihood, and neighbor-joining analyses of these sequence data strongly support the hypothesis that species of Phocascaris are nested within the clade of Contracaecum species hosted by phocid seals, and are more closely related to species of the Contracaecum osculatum complex than to other Contracaecum species. Alternative tree topologies representing Phocascaris as not nested within the C. osculatum complex were significantly worse interpretations of these sequence data. Phylogenetic analysis also provides strong support for the monophyly of all taxa (Contracaecum and Phocascaris) from phocid seals, which is consistent with Berland's (1964) proposal that such species form a natural group; however, his proposal to recognize all species in phocid seals as Phocascaris, with all species from birds as Contracaecum would result in a paraphyletic Contracaecum, according to the molecular phylogenetic hypothesis.

The ultrastructure of two types of secretory glands in the scolex of preadults of Proteocephalus longicollis is described for the first time in the present report. The gland cells contain extensive cisternae of granular endoplasmic reticulum and Golgi complexes, which participate in the production of secretory globules. Type I scolex glands produce electron-dense globules of various size. The secretory globules enter the secretory canal, openings of which were not observed in the preadults. The secretory product of type I was found at the inner sucker surface and in the tegument of the sucker edges. In addition, electron-dense globules in adult worms are secreted via an eccrine mechanism. Type II scolex glands are characterized by secretory globules of lower electron density and occur mainly in preadults. The electron-lucent, membrane-bound secretory globules are transported via microtubule-lined ducts opening to the exterior at the tegumental surface. Secretory globules of type II are released by an eccrine process.

In order to monitor the early phases of the development of Ascaris suum from domestic pigs, third-stage larvae, retrieved from the liver and the lungs, were studied by analyzing worm growth and length increase of individual transverse annuli in the cuticle. Material for study using light and scanning electron microscopy was obtained from experimental infections. The results show that the third-stage larva (not the second-stage) after emergence from the egg grows continuously, without an ecdysis in the liver. During growth, each annulus is split into a complex of 2 subannuli, each of which attains a bimodal appearance and is a prominent feature during a late phase of the third-stage larva. The results suggest that the first 2 molts occur inside the egg, a synapomorphic feature of the Ascaridoidea. The third-stage larvae of ascaridoids, with some functional similarities of the dauer-larva stage of Caenorhabditis sp., facilitate transmission of these parasitic worms to the digestive tract of the vertebrate final host (utilizing the tracheal route in A. suum), where the third and the fourth molts take place.

The ultrastructure of five types of presumed sensory receptors in the scolex of preadults of Proteocephalus longicollis is described. Two types of nonciliate sensory receptors are situated on the inner surface of the lateral sucker. They differ from each other in the shape, presence, or absence of a large rootlet, electron-dense collars, desmosomes, microtubules, and/or vesicles. In addition, three types of ciliate sensory receptors are found along the edges of the lateral suckers. They can be differentiated by the length of the cilium, by the number of electron-dense collars (one or two), and by types of vesicles. Four types of vesicles were found inside the ciliate sensory receptors. One type of ciliate sensory receptor occurring in preadults differs markedly from any of the sensory receptors previously described in adult P. longicollis.

The normal tissue migration of Ascaris suum in the pig host involves larval development in the liver accompanied by considerable pathological changes. The vast majority of larvae that reach the small intestine are later expelled by unknown mechanisms. We show that when migration through the liver is bypassed by inoculation of pigs with an intravenous dose of larvae hatched in vitro, the larvae not only complete migration and return to the small intestine, but they also seem to have a greater chance of survival to adulthood. This technique offers new possibilities for studies on specific lung involvement in protective immunity, provides valuable information for the understanding of self cure by larval expulsion, and adds to our understanding of the evolution of migration of Ascaris larvae in tissues.

Studies of the morphology of Ascaris suum larvae developing in the egg during embryonation in vitro at room temperature showed that 2 molts take place within the egg. The first larval stage (L1) appeared in the egg after 17-22 days of cultivation, the first molt to the second larval stage (L2) took place from day 22 to day 27, and the second molt to the third larval stage (L3) started on day 27 and continued during the 60-day observation period. Infectivity of the eggs was studied by oral egg inoculation in mice and showed that the L3 are the infective stage for mice. Molting to the L3 stage occurs gradually over a period of 2-6 wk, and it is recommended to have an additional maturation period so the infectivity of an egg batch may reach maximum level.

Two prominent, asymmetrically placed cuticular somatic sensilla, called centrids, are reported in Ascaris suum Goeze, 1782, the pig roundworm. The right centrid is situated much more anteriorly on the body than is the left one. The centrids are globular in the fourth-stage larva and obviously void of an apical pore, suggesting at least a tactile function. In adult worms, the centrids are platelike, lacking a globular expansion. The observation on the presence of asymmetrically placed centrids in A. suum gives further impetus to the importance assigned to sense organs in the classification and identification of nematodes. The name centrid was originally chosen to indicate the placement of the papillae in the midbody region of worms. The name centrid, rather than, e.g. postdeirid, is proposed to be used when denoting asymmetrically oriented midbody sensilla among the Ascaridida and papillae, when shown homologous to these, of species within the Rhabditea generally. This proposal is in line with the name "Mittelkörperpapillen" originally adopted to denote homologous sensillae in Cucullanidae (Seuratoidea) by Törnquist in 1931.

For studying the morphogenesis of the adult stage of Ascaris suum, worms were obtained from experimentally infected domestic pigs. Structural and morphometric features of A. suum are analyzed by light and scanning electron microscopy. It was shown that the increase in length of the worm from days 35 to 56 is based on a region-specific lengthening of individual transverse annuli in the cuticle. An increased worm size also results in an increased diameter of different cuticular sense organs. It is shown that a pair of lateral midbody papillae, the centrids, are prominent sensilla in the adult male and female worm. The centrids have an asymmetric placement, the right centrid being more anterior on the worm than the left.

The ultrastructure of six type of putative sense receptors including three nonciliate (Types I-III) and three ciliate (Types IV-VI) types found in the tegument of the scolex of adult Proteocephalus exiguus has been described for the first time. Type I has a simple tegumental sensory ending, containing one electron-dense collar, circular septate desmosome, electron-lucent vesicles and microtubules. Type II is represented by a receptor with a large rootlet. Type III is a receptor with a very long cross-striated rootlet, with two electron-dense collars and septate junction. The ciliated receptors differ in the length of the cilium, in the number of electron-dense collars and in the shape of sensory bulb. A comparison of structural features of receptors in different systematic group within Platyhelminthes is made.

In spite of the vast distribution and considerable impact on human and animal health of Ascaris suum and A. lumbricoides, little is known of the sexual biology and reproductive capacity of these intestinal nematodes. By oral transfer of adult female worms to previously parasite-naive pigs we show that in the absence of males the egg production ceases after 2-3 weeks. Such females readily resume egg production a few days after oral transfer of male worms. These observations throw light on an important aspect of Ascaris biology, but also pave the way for possible experimental interbreeding between the human and pig Ascaris species.

Neuropeptides and serotonin in the cestode, Proteocephalus exiguus: an immunocytochemical study. International Journal for Parasitology 25: 673-682. Neuropeptide F (NPF), RFamide and serotonin (5-HT) immunoreactivities have been detected in the nervous system of P. exiguus procercoids and adults, using an indirect immunocytochemical technique in conjunction with confocal scanning laser microscopy. The peptidergic nervous system of the procercoid is well developed, with two brain ganglia, three pairs of longitudinal nerve cords, transverse ring commissures and nerves in the suckers, all showing NPF-immunostaining. Strong NPF- and RF-immunostaining was observed in the CNS and PNS of the adult worm. The distribution patterns of the two neuropeptides were similar. Immunoreactivity for 5-HT was found only in the CNS.

Hatched, ensheathed third-stage larvae of Contracaecum osculatum, 300-320 microns long, were shown to be infective to copepods, to nauplius larvae of Balanus and to small specimens of fishes (sticklebacks, O-group eelpout). Other fishes such as gobies and small flatfishes became infected by ingesting infected crustaceans. Cod were infected by being given infected small fishes. In the crustacean paratenic hosts, little growth of the larvae occurred, if any. In the liver sinusoids of sticklebacks and gobies the length of most of the unencapsulated third-stage larvae had not even doubled within 6 months of infection. The fate of larvae (max. 2 mm long) given to cod via infected intermediate fish hosts was apparently decided by the size of the larvae only. Small larvae became encapsulated and eventually died in the liver and wall of the gastrointestinal tract. Larger larvae migrated to the liver parenchyma, where some grew to a length of as much as 10 mm. The growth of the larvae in sticklebacks was shown not to be affected by an increase in temperature (infected fish being transferred from 8 degrees to 14 degrees and 20 degrees C), by the intensity of infection and, partly, by the age of infection (e.g. some 2-week-old and 6-month-old larvae were of identical size). In the liver and mesentery of plaice the third-stage larvae developed via copepod paratenic hosts to infectivity (i.e. to more than 4 mm in length), showing that the life cycle may be completed with an optional paratenic invertebrate host and only one intermediate fish host.(ABSTRACT TRUNCATED AT 250 WORDS)

Two Proteocephalus species, P. neglectus La Rue, 1911 and P. exiguus La Rue, 1911, parasites of salmonid and coregonid fishes, were compared morphologically, biometrically, and electrophoretically. The study revealed that the two taxa cannot be differentiated by the morphological criteria used. No fixed allelic difference was found. In all, 12 of 13 enzymes detected by isoelectric focusing exhibited virtually identical isoenzyme profiles in both species. Only in the glutamate oxaloacatate transaminase enzyme locus was a difference observed. The negligible differences in zymograms and morphology, including similar biometric variability of the taxa studied, suggest that the species could be conspecific.

In Contracaecum osculatum Rudolphi, 1802 (Nematoda, Anisakidae) the first and the second ecdyses occur inside the egg. Larvae forced out from the eggs by coverslip pressure are surrounded by 2 cuticles, revealing 2 previous ecdyses. It is thus the third-stage larva that emerges from the hatched egg and not the second-stage larva as previously believed. The cuticle of the first-stage larva is thin, smooth, and remains in the egg, whereas the cuticle of the second-stage larva is thick, striated, and, serving as a cover, loosely ensheaths the released larva.

The peptidergic innervation of sensory structures in two species of nematodes, Ascaris suum (order Ascaridida, family Ascarididae) and Cystidicola farionis (order Spirurida, family Cystidicolidae) was studied. Immunocytochemical methods were used for localization of FMRF-amide-like neuropeptides in the nervous system. Immunoreactivity to FMRF-amide, RF-amide and SALMF-amide was detected in the central nervous system of the species studied, and also in the cephalic papillary nerves, in axons of the amphids and the deirids, and in nerves innervating caudal papillae.

Infective, third-stage larvae of the genus Contracaecum from fish were cultured in vitro and fed to laboratory animals in order to obtain later developmental stages to permit their specific identification. The in vitro incubation was unsuccessful. In orally infected laboratory rats and hamsters, fourth-stage larvae were obtained from the stomach at 2-5 days postinfection (p.i.), but no adult worms developed. Larvae introduced surgically into the body cavity of laboratory rats yielded some adult worms from day 42 onwards. Adult males were identified as Contracaecum osculatum.

A survey revealed that Onchocerca tarsicola Bain & Schulz-Key, 1974 is a widespread parasite among reindeer in northern Finland. Of 407 animals studied from 12 reindeer herds, 124 (30.5%) were infected. There was a marked difference in infection levels between different reindeer herds and the frequency as well as the intensity of infection was highest in old animals whereas the parasites were rare in yearlings.