Ultrastructure of the apical glandular region of the scolex of Proteocephalus torulosus (Cestoda: Proteocephalidae)

In the apical glandular region of the adult Proteocephalus torulosus (Batsch, 1786), two types of eccrine gland cells are present. The first type of unicellular gland produces large electron-dense granules of various sizes. The second type contains small electron-dense granules. Most cells form glands with large granules; glands with small granules are infrequent. The secretion of both types of gland cells is concentrated in the apical parts of the cyton and in the ducts opening to the exterior. On the scolex of P. torulosus, there are regional structural differences of the microthrix border. The apical glandular region bears filamentous microtriches only. On the remaining frontal part, surrounding the glandular region, there are blade-like and filamentous microtriches. The lateral parts of the scolex and suckers bear blade-like microtriches. Possible functions of both types of gland cells and different parts of the scolex microthrix border are discussed. The unique structure of the frontal part of the scolex of P. torulosus and its differences from Proteocephalus macrocephalus, P. longicollis and P. percae correlate well with the putative basal phylogenetic position of P. torulosus among European species of Proteocephalus.     

Tapeworms (Cestoda: Proteocephalidea) of firewood catfish Sorubimichthys planiceps (Siluriformes: Pimelodidae) from the Amazon River

A survey of proteocephalidean cestodes found in the firewood catfish Sorubimichthys planiceps (Spix et Agassiz) from the Amazon River is provided. The following taxa parasitic in S. planiceps are redescribed on the basis of their type specimens and material collected recently in the Amazon River, near the type localities in Brazil, and in Iquitos, Peru: Monticellia lenha Woodland, 1933; Nomimoscolex lenha (Woodland, 1933) (syn. Proteocephalus lenha Woodland, 1933); and Monticellia megacephala Woodland, 1934, for which a new genus, Lenhataenia, is proposed, with L. megacephala (Woodland, 1934) comb. n. as its type and only species. The new genus is a member of the Monticelliinae, i.e. has all genital organs in the cortex, and is most similar to Chambriella in possessing biloculate suckers and lacking a metascolex. It differs in the morphology of the cirrus-sac that contains a strongly coiled, thick-walled internal sperm duct (vas deferens) and a muscular cirrus of the appearance typical of most proteocephalideans, whereas that of Chambriella is sigmoid, with voluminous, tightly sinuous thick-walled internal sperm duct. In addition, Lenhataenia possesses a well developed internal musculature, whereas the internal musculature of Chambriella is weakly developed, formed by a low number of muscle fibres. The scolex morphology and distribution of microtriches of Peltidocotyle lenha (Woodland, 1933) (syn. Othinoscolex lenha Woodland, 1933 and Othinoscolex myzofer Woodland, 1933), Chambriella sp. and Choanoscolex sp. are described using scanning electron microscopy. The two latter taxa may be new for science and are reported from S. planiceps for the first time.     

Studies on the development of the cestode Proteocephalus neglectus La Rue, 1911 (Cestoda: Proteocephalidae) under experimental conditions

A part of the life cycle of Proteocephalus neglectus La Rue, 1911, a parasite of trout, starting from release of eggs from mature parasites into water, to the early phase of development in the definitive host, was studied under experimental conditions. Special regard has been paid to development in the intermediate host, copepod Cyclops strenuus. Some oncospheres in eggs kept in water at 5 and 10 degrees C remained infective for 20-25 days. The percentage of infected copepods depended on the length of their contact with parasite eggs. Cestode larvae (cercoscoleces) were formed in the intermediate host on days 8-10 p.i. at the temperatures of 21-22 degrees C, on days 18-21 at 15 degrees C, on days 24-28 at 10 degrees C, and on days 59-65 at 6 degrees C. Most larvae, including infective cercoscoleces, were localized in the cephalothorax of the intermediate host, particularly in its first segment. This localization did not change during their development. The infectivity of cercoscoleces was verified by experimental infection of Salmo gairdneri fry. The development of the cestode in this definitive host was observed for 17 days after infection at 10 degrees C. The finding of P. neglectus cereoscoleces in fish of the families Cottidae and Cyprinidae on day 2 after experimental infection indicates that these larvae can survive for a short time in atypical fish hosts.     

Karyological investigations of Caryophyllaeus laticeps (Pallas, 1781) (Cestoda: Caryophyllidea).

Mitotic and meiotic chromosomes of Caryophyllaeus laticeps (Pallas) from Rybinsk reservoir were studied using air-drying techniques. It was established that the diploid set contains 20 metacentric chromosomes. The chromosomes are large--their mean absolute length ranges from 3.00 to 12.90 microns. The last pair of small homologues comprises only 3.4% of the total length of the complement. One specimen of C. laticeps with 2n = 21 (trisomic after the last pair of chromosomes) and one triploid specimen with 3n = 31 is described. Data on the comparative karyology of caryophyllids are discussed.     

First species of Ophiotaenia (Cestoda: Proteocephalidea) from Madagascar: O. georgievi sp. n., a parasite of the endemic snake Leioheterodon geayi (Colubridae)

Ophiotaenia georgievi sp. n. (Proteocephalidea: Proteocephalinae) is described from the intestine of endemic colubrid snake Leioheterodon geayi Mocquard (Colubridae) from Antananarivo in Madagascar. The new species is the first species of Ophiotaenia La Rue, 1911 reported from Madagascar. It differs from all Ophiotaenia species parasitic in African snakes in the possession of a three-layered embryophore of eggs (other African species have two-layered embryophore). Furthermore, O. georgievi can be distinguished by the number of testes (92-140), width of the scolex (225-235 jm), total body length (57 mm), cirrus-sac length/proglottis width ratio (19-32%), and number of lateral uterine diverticula (23-28 on each side). Ophiotaenia georgievi represents the second proteocephalidean cestode reported from Madagascar, the first one being Deblocktaenia ventosaloculata (Deblock, Rosé et Broussart, 1962), a parasite from Ithycyphus miniatus. A list of Ophiotaenia species parasitic in venomous and non-venomous snakes is provided and possible existence of other new congeneric species in snakes from Madagascar is discussed.     

Redescription of Proteocephalus bagri and p. Rhamdiae (Cestoda: Proteocephalidae), parasites of Rhamdia quelen (Siluriformes: Pimelodidae) from South America, with comments on morphological variation

The pimelodid fish Rhamdia quelen (Quoy et Gaimard, 1824) in South America harbours two species of proteocephalid cestodes, Proteocephalus bagri Holcman-Spector et Ma?é-Garzón, 1988 and P. rhamdiae Holcman-Spector et Ma?é-Garzón, 1988. These species are redescribed based on a detailed morphological study, supported by multivariate analysis (principal component analysis). Features distinguishing these species are: (1) the shape of proglottides, (2) the mean number of testes, (3) the topography of vitelline follicles, (4) the thickness of internal longitudinal musculature, (5) the mean number of uterine branches, (6) the ratio of cirrus pouch length to proglottis width, (7) the shape of ovary in mature and gravid proglottides and (8) the genital pore position in mature proglottides. The specific status of P. bagri and P. rhamdiae is confirmed and neotypes of both species are designated.     

Ritacestus gen. n. (Cestoda: Proteocephalidea) and redescription of R. ritaii comb. n., a parasite of Rita rita (Siluriformes) in India

A new genus, Ritacestus, is proposed to accommodate Ritacestus ritaii (Verma, 1926) comb. n. (syn. Proteocephalus ritaii), a parasite of the catfish Rita rita (Hamilton) in India. The new genus, which is placed in the Gangesiinae, is characterized by (i) a small, subspherical scolex formed by four large lobes separated from one another by longitudinal grooves, with a large, widely oval to pyriform rostellum-like apical organ, larger than suckers and possessing an apical hemispherical depression; (ii) paramuscular and cortical position of some vitelline follicles (most follicles are situated medullary); (iii) ventral and dorsal bands of vitelline follicles usually uninterrupted ventral to terminal genitalia and reaching to the posterior margin of proglottides; (iv) the vagina always anterior to the cirrus-sac; (v) a large size of the body (length up to 51 cm); and (vi) development of the uterus of type 2. In its morphology, especially shape of the scolex and apical organ, and paramuscular and cortical position of some vitelline follicles, Ritacestus resembles Postgangesia Akhmerov, 1969, but differs in the presence of a genital atrium (both genital pores of Postgangesia are separate), the anterior position of the vagina (almost always posterior in the latter genus), position of vitelline follicles in cross sections (dorsal and ventral bands in Ritacestus versus only a lateral band in the latter genus), and dorsal excretory canals indistinguishable in mature and gravid proglottides of R. ritaii (well developed in Postgangesia spp.). The type and only species of the genus, R. ritaii, is redescribed on the basis of new material from the type host from the Ganges River basin in India and its neotype is designated.     

Localization of some enzymes in polycephalic larvae of two species of the genus Multiceps (Cestoda).

The histochemical distribution of alkaline phosphatase (AIP), acid phosphatase (AcP) and nonspecific esterase (NE) has been determined in polycephalic larvae of the species Multiceps multiceps Leske, 1870 and M. endothoracicus Kirschenblat, 1948. In the scolex anlages of both species, an activity of these enzymes has been determined in sites associated with growth and with the transport of metabolites. In a young larva of M. multiceps, the activity of AIP, AcP and NE was strong in the entire proliferating bladder wall surrounding groups of scoleces, but absent in the remaining part of the bladder wall outside the area of these scolex groups. In young larvae of M. endothoracicus, AlP and NE activity was highest in the modified bladder wall forming a verrucose mound, and at the site of the opening of the invaginated canal. No activity of these enzymes was demonstrated in mature and aging larvae.     

Invalidity of three Palaearctic species of Triaenophorus tapeworms (Cestoda: Pseudophyllidea): evidence from morphometric analysis of scolex hooks

A comparative study of the scolex hook morphology of five species of tapeworms of the genus Triaenophorus Rudolphi, 1793 (Cestoda: Pseudophyllidea), parasites of pikes (Esox lucius L. and E. reichertii Dybowski) in the Palaearctic Region, was carried out. Measurements of scolex hooks of 81 plerocercoids and 492 adults from different hosts and regions were compared using basic statistics and forward stepwise linear discriminant analysis. The shape of the scolex and that of tridental hooks were found to be suitable only for differentiation of the taxa with a similar shape of hooks, i.e. Triaenophorus nodulosus (Pallas, 1781) from T. amurensis Kuperman, 1968, and T. crassus Forel, 1868 from T. meridionalis Kuperman, 1968 and T. orientalis Kuperman, 1968, respectively. In contrast, discriminant analysis did not enable reliable separation of specimens of individual taxa of these two morphological groups due to high intraspecific variability and overlaps between species. This was reflected in low classification efficiencies (average 83%) of all species of the T. crassus group, whereas all T. amurensis specimens were misidentified as T. nodulosus. The new data also considerably enlarge (up to twofold) the size range of the species described by Kuperman in 1968, which invalidates suitability of the most important discriminant characteristic, the width of the basal plate, for delimitation of Triaenophorus species. Based on the present data, all Kuperman's taxa are considered to represent only distinct geographical populations of T. nodulosus and T. crassus. As a result, T. anmurensis is synonymized with T. nodulosus, whereas T. orientalis is considered to be a synonym of T. crassus. Previous synonymisation of T. ineridionalis with T. crassus, first proposed by Dubinina (1987), is also accepted.     

Ophiotaenia bonneti sp. n. (Eucestoda: Proteocephalidea), a parasite of Rana vaillanti (Anura: Ranidae) in Costa Rica

Ophiotaenia bonneti sp. n. is described from the intestine of the frog Rana vaillanti Brocchi, 1877 (Anura: Ranidae) from San Gerardo, Guanacaste, Costa Rica. The new species is characterized by the testes 100-177 in number, the genital pores situated anteriorly, the osmoregulatory canals overlapping the testis field, the cirrus pouch length as 15-24% of proglottis width, and the uterus with 18-32 ramified diverticula on each side. It differs from the 23 known species of the genus Ophiotaenia La Rue, 1911, parasitic in amphibians, by one to several morphological characters. It differs from O. gracilis Jones, Cheng et Gillespie, 1958, the most morphologically similar species, in the sucker diameter in % of scolex diameter and in the morphology of the eggs - funnel-like depression and embryophore closely investing the oncosphere in O. gracilis. We generally observe a very low mean prevalence of the Proteocephalidea in Neotropical amphibians (about 0.41%-3%), but in the case of some host species, the prevalence can reach up to 25%. We conclude that these cestodes exhibit a strict host specificity of the oioxene type. Ophiotaenia junglensis Srivastava et Capoor, 1980 is considered a species inquirenda. Batrachotaenia hernandezi (Flores-Barroeta, 1955) becomes Ophiotaenia hernandezi (Flores-Barroeta, 1955) comb. n., B. tigrina (Woodland, 1925) becomes O. tigrina (Woodland, 1925) comb. n. and B. ceratophryos (Parodi et Widakowich, 1916) becomes O. ceratophryos (Parodi et Widakowich, 1916) comb. n.     

Bothriocephalidean tapeworms (Cestoda) from the blackfish, Centrolophus niger (Perciformes: Centrolophidae)

Bothriocephalidean tapeworms parasitic in the blackfish, Centrolophus niger (Gmelin) (Perciformes: Centrolophidae), are redescribed on the basis of the evaluation of freshly collected specimens and museum material. This evaluation enabled us to supplement species diagnoses by new morphological characters of potential use for phylogenetic analyses, including the data from scanning electron microscopical observations, and to provide a key to identification of the following four species occurring in this fish: Amphicotyle heteropleura (Diesing, 1850); Milanella familiaris Kuchta et Scholz, 2008 (both Triaenophoridae); Bothriocotyle solinosomum Ariola, 1900; and Echinophallus wageneri (Monticelli, 1890) (both Echinophallidae). Large spiniform microtriches were observed on the surface of the posterodorsal margin of segments of B. solinosomum, E. wageneri and M. familiaris. The invalidity of Atelemerus Guiart, 1935, first proposed by Bray et al. (1994), is supported by the present data and its type species, A. acanthodes Guiart, 1935, is newly synonymised with E. wageneri.     

Orthoptera as intermediate hosts of Staphylocystis furcata (Stieda, 1862) (Cestoda: Hymenolepididae)

Cysticercoids of Staphylocystis furcata (Stieda, 1962), the adults of which parasitize the shrews (Soricidae), were found in the thoracic and abdominal cavities of orthopterous insects (Orthoptera, Acridioidea) belonging to five species: Chorthippus apricarius (L.), Chorthippus paralellus (Zett.), Omocestus viridulus (L.), Chrysochraon brachypterus (Ocsk.), and Chrysochraon dispar (Germ.). The cysticercoids are described and their incidence in both sexes of the examined intermediate hosts is compared.     

Ultrastructure of Archigetes sieboldi (Cestoda: Caryophyllidea): relationship between progenesis, development and evolution

Ultrastructural characteristics of progenetic and monoxenic Archigetes sieboldi Leuckart, 1878 from the oligochaete Limnodrilus hoffmeisteri Claparède are described. Our observations demonstrate that progenetic Archigetes sieboldi shares characteristics of both larval (progenetic) and adult stages. The primary larval characteristics are: the presence of a cercomer; a surface filamentous coat covering the whole worm; the presence of the penetration glands and the absence of tegumental ones; wide sarcoplasmic processes connecting the circular and longitudinal external tegumental muscles; the absence of the dense homogenous zone of the basal lamina beneath the epithelial cytoplasm of all reproductive organs and ducts; non-functional gonopores; and an orthogonal plan of nervous system with three pairs of longitudinal nerve trunks. The principle adult characteristics are: oogenesis, spermiogenesis and vitellogenesis that produce fertilized eggs; the uterine glands; a well-developed longitudinal tegumental muscle layer between tegumental cytons; and the presence of different microtriches. As a result of this progenetic development there has been a secondary reduction in the life cycle of A. sieboldi. It is postulated that a similar process of progenesis may have played a major role in the early evolution of the Caryophyllidea by first appearing in a plerocercoid stage of an ancestral strobilate cestode from fish.     

Descriptions of two new freshwater neotropical species of Rhinebothrium (Cestoda: Rhinebothriidea) from Potamotrygon motoro (Chondrichthyes: Potamotrygonidae)

Two new species of Rhinebothrium (Cestoda, Rhinebothriidea) from potamotrygonid stingrays in the Neotropical region are herein described, which raises the total number of Rhinebothrium species known from Neotropical freshwaters to five. Rhinebothrium corbatai sp. n., and Rhinebothrium mistyae sp. n. were both collected from Potamotrygon motoro (Müller et Henle), captured in four tributaries of the Paraná River in Santa Fé Province, Argentina. The new species can be distinguished from their congeners, and from each other, by a combination of various features, including worm size (length and number of proglottids), number of loculi per bothridium, microthrix pattern, size of the cirrus sac, and the extent of the vas deferens. The discovery of these new species from P. motoro supports the pattern of high host specificity in this cestode genus, and reinforces the notion that some of the previous records of the enigmatic R. paratrygoni may correspond to new species of Rhinebothrium yet to be described.     

Three new species of Echinobothrium (Cestoda: Diphyllidea) from Indo-Pacific stingrays of the genus Pastinachus (Rajiformes: Dasyatidae)

Three new species of diphyllidean cestodes are described from stingrays of the genus Pastinachus from the Indian and Pacific Oceans. All three new species differ from all but 10 of the 36 valid species of Echinobothrium van Beneden, 1849 in that they bear lateral hooklets arranged in a continuous band across each lateral surface of the rostellum joining the groups of dorsal and ventral apical hooks, rather than arranged in distinct dorsal and ventral groups, on each side of the apical hooks. Echinobothrium nataliae sp. n. ex Pastinachus solocirostris off Borneo differs from other relatives in the following combination of characters: number of spines in each column on the cephalic peduncle, number of lateral hooklets and number of apical hooks. Echinobothrium reginae sp. n. ex Pastinachus cf. sephen off Madagascar differs from all congeners in the following combination of characters: number of hooklets and number of spines on the cephalic peduncle. Echinobothrium vojtai sp. n. from an undescribed species of Pastinachus off Borneo differs from its congeners in the following combination of characters: number of hooklets, number of apical hooks and number of spines in each column on the cephalic peduncle. The hook formula was modified to accommodate species with lateral hooklets arranged in a continuous band as follows: {(LH) AH(A)/AH(B)}, where (LH) is the total number of lateral hooklets in a band. A table of all nominal species of Echinobothrium, showing their taxonomic status, type host and locality, number of peduncle spines in a column and hook formula, is presented. Macrobothridium djeddensis and Macrobothridium sinensis are transferred to Echinobothrium. In addition, Echinobothrium deeghai is considered as a species inquirenda.     

Early development of Khawia sinensis Hsü, 1935 (Cestoda: Caryophyllidea), a carp parasite

The development of the tapeworm Khawia sinensis parasitizing carp (Cyprinus carpio L.) has been studied from the release of cestode eggs into water to the formation of infective procercoids in the intermediate host under laboratory conditions. The rate of embryonal development is greatly influenced by the water temperature. While at 5 degrees C the development of oncospheres was not recorded, at 10-12 degrees C, 15 degrees C, 20-22 degrees C, and 23-24 degrees C oncospheres were fully formed after 57, 42, 21 and 16 days, respectively. Infectivity of oncospheres was confirmed by successful experimental infection of the intermediate hosts: Tubifex tubifex and Limnodrilus udekemiamus (Oligochaeta: Tubificidae). Fully formed procercoids infective for the definitive host were found in the intermediate host from 52 days of development at 20-22 degrees C. From the third week of development in the intermediate host, most of the parasite larvae were located in the anterior part of the tubificid body, mainly between 8th and 15th segments.     

Fine structure of the female reproductive ducts of Cyathocephalus truncatus (Cestoda: Spathebothriidea), from salmonid fish

The fine structure of the ovary, ovicapt, oviduct, fertilisation canal, vitelline ducts, vitelline reservoir, ovovitelline duct, ootype and Mehlis' gland, and proximal, middle and distal parts of the uterus of the spathebothriidean cestode, Cyathocephalus truncatus (Pallas, 1781), from salmoniform fish, has been studied for the first time by transmission electron microscopy (TEM). Emphasis was given to characteristics which might shed light on the unclarified phylogenetic position of spathebothriideans, belonging among the most basal tapeworms (Eucestoda). New for cestodes is the finding of a multinucleate cell that plugs the ovicapt lumen. The morphology of the proximal part of the oviduct resembles that of the pseudophyllidean tapeworm Diphyllobothrium latum. After fertilisation in the fertilisation canal, vitellocytes of C. truncatus become associated with fertilized oocytes in the ovovitelline duct. Only one type of Mehlis' gland secretory cell is present. The eggs with electron-dense eggshells containing large pores first appear in the proximal part of the uterus. The middle portion of the uterus has well-developed uterine glands. The distal portion of the uterus has apical microtriches. Ultrastructural data on the female genital system of C. truncatus are compared and discussed with those for other cestodes. However, on the basis of available ultrastructural data it is not possible to conclude whether the Spathebothriidea are phylogenetically closer to the Caryophyllidea or to the Pseudophyllidea.     

A standardised terminology of the embryonic envelopes and associated developmental stages of tapeworms (Platyhelminthes: Cestoda)

Over the past 40 years, much has been published on the ultrastructure and cellular development of embryonic structures in a wide range of cestodes. However, the literature contains many discrepancies in both terminology and interpretations because of the facts that these organisms are phylogenetically diverse within their respective orders and families, the habitats that affect embryonic envelope structure are diverse, and the work has been done in various laboratories around the world. This review and synthesis was initiated by a working group of biologists from around the world convened at the Fifth International Workshop on Cestode Systematics and Phylogeny in Ceské Budejovice, at the Institute of Parasitology of the Biology Centre, Academy of Sciences of the Czech Republic. It brings together the data from published work and establishes a uniform terminology and interpretation based on the data as they are presented. A consensus was reached for standardised definitions of the oncosphere, hexacanth, coracidium, embryonic envelopes, outer envelope, inner envelope, embryophore, vitelline capsule, shell, and outer coat. All of these are defined as components of the embryo or its vitellocyte-derived or uterine-derived coatings.