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Using biochemical genetic methods, we have distinguished 2 sibling species in the complex Bothrimonus nylandicus (Schneider, 1902), which infest 2 congeneric species of sole (Solea lascaris and Solea impar) on European coasts (Atlantic and Mediterranean). Neither of the parasite species is specific for either of the sole species, but one of them is present all year round, whereas the other is absent in the autumn and winter and only appears in the spring, subsequently disappearing at the end of the summer. Only S. impar lives in the Mediterranean, and is equally infested by both cestodes, whereas both species occur in the Atlantic and each of them is preferentially infested by 1 species of cestode. The shortness of the adult stage of the parasite in the definitive host and the presence of 2 life-cycles associated with competition between the 2 hosts in the Atlantic could be responsible for the biological differences observed and for maintaining the sibling species in sympatry.
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The expression of six actin genes was examined in adult and plerocercoid Diphyllobothrium dendriticum tapeworms using in situ hybridization. On the basis of their structures, these genes are divided into three groups, the cestoda-I, -II and -III actins. Current studies show that the expression of actins belonging to different groups vary to a great extent. The three cestoda-I actins are expressed primarily in muscle cells of both adult and plerocercoid tapeworms, the expression being restricted to fewer cells in the plerocercoid larva. The two cestoda-II actins are cytoplasmic actin isoforms, expressed in a variety of cells, i.e. in cells dividing, differentiating and migrating. Expression of the cestoda-III actin gene is detected merely in the peripheral part of the outer parenchyma, mainly in the tegument cell bodies. This pattern is very weak in plerocercoids. The results indicate that actins also in D. dendriticum can be divided into cytoplasmic and muscle-specific isoforms. In this organism, one major pattern of muscle actin gene expression (cestoda-I) and two major patterns of non-muscle actin gene expression (cestoda-II and -III) were found.
Caulobothrium longicolle (Linton, 1890) and Phyllobothrium gracile (Weld, 1855) (Cestoda: Tetraphyllidea, Phyllobothriidae) have the same embryonic development with the following characteristic data: --a small number of vitelline cells (2 or 3) pass with the zygote in the ootype;--a non operculate thin egg-shell;--the entire and equal zyhote cleavage following by unequal divisions leading to the formation of four blastomere types (Macromeres, secondary Macromere, Mesomeres and Micromeres);--the differentiation of two syncytial embryonic envelopes during the preoncospheral phase. The outer envelope encloses the vitelline material remnant and three Macromeres among which the secondary Macromere. The inner envelope or embryophore, originates from five or six Mesomeres;--the presence of the oncospheral membrane;--the Phyllobothriidae ontogenesis is similar to that of the Onchobothriidae. By their embryonic features, the Tetraphyllidea are close to the Cyclophyllidea. This similarity suggests a phylogenic relationship between those two Cestoda orders.
The redescription of the cestoda Hepatocestus hepaticus (Baer, 1932) was made on the original material from the Western Siberia shrews in connection with the first registration this species at shrews within the east palearctic. The analysis of the morphology of the H. hepaticus from the western Siberian populations of shrews hadn't reveal essential morphological distinctions as compared with their western palearctic populations except that we didn't found the uterine capsules in the specimens studied by us. Crocidura sibirica Dukelsky was been registered as the definite host of this cestoda at first.
DNA/DNA hybridization has been carried out to establish the evolutionary relationships among several host-specific bothriocephalid tapeworms species (Cestoda: Platyhelminthes). Comparative anatomy is not informative for deciphering the relationships among these sibling morphological taxa, and clearcut genetic differences have previously identified seven biological species which are each highly specific to a single host. We show that two species (Bothriocephalus gregarius and B. renaudii) infesting the same host (turbot: Psetta maxima) in two different geographic areas are not sister-taxa. Moreover, a strong decrease in the amount of DNA change is observed in one species of tapeworm, documenting a marked heterogeneity of rates of nucleotidic substitution among these very closely related organisms. Based on these observations, different hypotheses are developed for understanding the evolutionary history of this assemblage of parasites, suggesting that host-switching has played an important role in the recent past.
Interrelationships of the tapeworms (Platyhelminthes: Cestoda) were examined by use of small (SSU) and large (LSU) subunit ribosomal DNA sequences and morphological characters. Fifty new complete SSU sequences were added to 21 sequences previously determined, and 71 new LSU (D1-D3) sequences were determined for the complementary set of taxa representing each of the major lineages of cestodes as currently understood. New sequences were determined for three amphilinidean taxa, but were removed from both alignments due to their excessively high degree of divergence from other cestode sequences. A morphological character matrix coded for supraspecific taxa was constructed by the modification of matrices from recently published studies. Maximum-parsimony (MP) analyses were performed on the LSU, SSU, LSU+SSU, and morphological data partitions, and minimum-evolution (ME) analyses utilizing a general time reversible model of nucleotide substitution including estimates of among-site rate heterogeneity were performed on the molecular data partitions. Resulting topologies were rooted at the node separating the Gyrocotylidea from the Eucestoda. The LSU data were found to be more informative than the SSU data and were more consistent with inferences from morphology, although nodal support was generally weak for most basal nodes. One class of transitions was found to be saturated for comparisons between the most distantly related taxa (gyrocotylideans vs cyclophyllideans and tetrabothriideans). Differences in the topologies resulting from MP and ME analyses were not statistically significant. Nonstrobilate orders formed the basal lineages of trees resulting from analysis of LSU data and morphology. Difossate orders were basal to tetrafossate orders, the latter of which formed a strongly supported clade. A clade including the orders Cyclophyllidea, Nippotaeniidea, and Tetrabothriidea was supported by all data partitions and methods of analysis. Paraphyly of the orders Pseudophyllidea, Tetraphyllidea, and Trypanorhyncha was consistent among the molecular data partitions. Inferences are made regarding a monozoic (nonsegmented) origin of the Eucestoda as represented by the Caryophyllidea and for the evolution of the strobilate and acetabulate/tetrafossate conditions having evolved in a stepwise pattern.
The genetic diversity of two samples of Cestoda (Bothriocephalus funiculus, Renaud and Gabrion, 1984) parasitizing two sympatric teleostean species was assessed using random amplified polymorphic DNA (RAPD). A total of 72 Bothriocephalus were analyzed individually, and electrophoretic analysis of the amplification products of 65 primers among the 68 tested revealed monomorphic patterns, reflecting the close genetic relatedness within and between the parasites of the two samples. However, 3 primers showed polymorphic patterns at 6 RAPD sites. Analysis of the distribution of these genomic fragments, assuming random mating, showed strong linkage disequilibria (only 8 genetic combinations were observed among the 32 expected). Two genetic entities displaying a high degree of host specificity were evidenced within our two samples of funiculus. This powerful molecular technique can be used as a diagnostic tool in studies concerning the biodiversity of related genetic entities and could have broad applications in parasitology.
The genus Digramma (Cestoda: Pseudophyllidea) described by Cholodkovsky in 1915 differs from the genus Ligula only by the number of the reproductive organs per proglottis. However, the occurrence of transitional forms in Digramma raises much confusion concerning its generic validity. In the present study, cestodes previously designated as Digramma and Ligula were collected from lakes in the lower and middle reaches of the Yangtze River, and also from Qinghai Lake on Qingzang plateau, China. The entire internal transcribed spacer of the ribosomal DNA (ITS rDNA) and 5' end of 28S rDNA were compared between the Digramma and Ligula specimens. The low level of nucleotide variation between the two genera may imply that cestodes in the genus Digramma are paraphyletic to the Ligula genus, and Digramma is a synonym of Ligula. However, whether previously identified Digramma cestodes represent different species in the genus Ligula requires further investigation.
The manner in which the flatworm, Hymenolepis diminuta (Cestoda), regulates the transport of glucose and Na+ across the brush border was examined. While the presence of an unstirred region in the brush border may favor the reabsorption of leaked glucose, some leaked glucose was lost to the ambient medium. This loss was markedly enhanced by preloading the worms with glucose and by removing Na+ from the incubation medium. Since glucose and Na+ influxes are coupled, glucose leakage stimulated the influx of 22Na+. However, this 22Na+ influx was balanced by a simultaneous increased 22Na+ efflux. The presence of phlorizin inhibited both unidirectional fluxes of 22Na+ indicating that efflux of 22Na+ occurred by countertransport; countertransport of [14C] glucose appeared to be negligible. A model has been proposed in which the transport of glucose and compensating transfers of Na+ across the membrane occur via the same carrier.
The gross morphology and ultrastructure of the different parts of the protonephridial system of the monozoic tapeworms Gyrocotyle urna and Amphilina foliacea are described. The terminal cell in both species has numerous cilia which are interconnected and extend into the lumen of the first canal cell. The filtration area is built up from projections of two cells, the terminal cell and the first canal cell. The first canal cell forms a solid hollow cylinder without a cell gap and a desmosome as found in Neodermata other than cestodes and Udonella. In Gyroctyle the nucleus of the first canal cell is located in the wall cytoplasma whereas more distally located ductules of both species have subepithelial cell bodies containing the nuclei. In both taxa the protonephridial canal system is reticulate. In Amphilina the distal canals lack non-terminal ciliary flames, such ciliary tufts can be found in the larger capillaries of Gyrocotyle. The capillary cilia have rootlets and the ultrastructure of the duct wall cytoplasm containing large numbers of vesicles indicates highly active transport processes. The morphology of the protonephridial systems is discussed with regard to the evolution of Neodermata (especially of the Cestoda) and the function of the protonephridial system in cestodes as a probable organ of nutrient distribution.
Thysanosoma actinioides Diesing, 1834 (Cestoda: Anoplocephalidae) parasitizes domestic and wild herbivores, and its life cycle has not yet been completely elucidated. The aim of this study was to analyze the role of oribatid mites as intermediate hosts of T. actinioides. The work was carried out at a Merino sheep breeding farm situated in the Pre-Cordillera region near Bariloche City, Río Negro Province, Argentina. The proglottids of T. actinioides were obtained from feces of infected sheep. In the laboratory, they were placed in the plastic wells with oribatid mites. The species of oribatids used in this experimental trial were Zygoribatula striassima Hammer, 1962 (Family Oribatulidae) and Oribatella spp. Banks, 1895 (Family Oribatellidae). Both species became infected with larval stages of T. actinioides. However, the infective cysticercoid stage did not develop.
Polyonchobothrium scleropagis (Cestoda: Pseudophyllidea) is described as a new species from the Australian osteoglossid fish Sclerophages leichardti Günther.
A total of 21 amino acids were detected in the present investigations on three species of Gangesia (Cestoda: Proteocephalata) viz. G. bengalensis Woodland, 1924, G. hanumanthai Seth & Capoor, 1982 and G sanehensis Malhotra et al., 1981. The study was conducted in a sub-humid region around Allahabad, India. The implications of amino acid utilization in metabolic activities of fish tapeworms have been discussed.
We describe Paranoplocephala serrata n. sp. (Cestoda, Anoplocephalidae) from collared lemmings Dicrostonyx torquatus and D. groenlandicus (Arvicolinae, Rodentia) in Arctic Siberia and North America. The new species was recorded from the Yamal Peninsula (type-locality), Yana Delta, Kolyma Delta, Wrangel Island, Alaska and Victoria Island/Kent Peninsula (Northwest Territories). P. serrata n. sp. is characterised by a long, ribbon-like strobila, distinctly serrated segments, a small scolex, unilateral or infrequently alternating genital pores and testes confined to the antiporal part of the segment. It differs from the related species (Andrya bairdi, Parandrya feodorovi and Paranoplocephala manseri) by several morphological features, including the distribution of testes (several testes antiporal to ventral longitudinal osmoregulatory canal), structure of the cirrus-sac and vagina, and large eggs (0.053-0.068 mm in the type-material). The material of P. serrata n. sp. from North America differs from the Siberian material by the shorter cirrus-sac, smaller dimensions of the female reproductive organs, larger seminal receptacle and larger eggs. However, the statistical differences in the dimensions of reproductive organs mainly reflect the larger size of mature segments in Siberian specimens compared with North American specimens. The main diagnostic features, i.e. the size and form of scolex and suckers, number and distribution of testes, position of female glands, vagina/cirrus-sac ratio and morphology of reproductive organs, do not differ markedly between the Palaearctic and Nearctic specimens. According to the structure of the early-stage uterus, A. bairdi Schad, 1954 belongs to the genus Paranoplocephala. Parandrya Gulyaev & Chechulin, 1996 is probably a synonym of Paranoplocephala. A redescription is provided for Paranoplocephala bairdi n. comb.
The authors describe and illustrate Wardium canarisi n. sp. (Cestoda: Hymenolepididae), an intestinal parasite of Arenaria melanocephala (Aves: Charadrii) from Alaska, characterised by a strobila 20-40 mm long, 10 aploparaksoid hooks 19-21 microm long, a short cylindrical cirrus (40 microm) covered with very minute spines (0.2 microm), and a short (8-18 microm) and extremely narrow (1 microm) copulatory vagina. These characters have no equivalent, even approximate, among the 27 species of Wardium parasitic in the Charadrii which are reviewed. The genus Debrosia Spassky, 1987 appears to be justified.