Redescription and Molecular Assessment of Relationships Among Three Species of Echeneibothrium (Rhinebothriidea: Echeneibothriidae) Parasitizing the Yellownose Skate, Dipturus chilensis, in Chile

Much progress has recently been made in revising the taxonomic assignments of genera originally classified in the polyphyletic "Tetraphyllidea." Many of these genera, including Echeneibothrium, were accommodated in the order Rhinebothriidea. However, beyond this larger taxonomic action, little work has been conducted on this genus over the past 50 yr. Consequently, the criteria used for characterizing species of Echeneibothrium have lagged behind those typically used in more modern descriptions of elasmobranch-hosted cestode taxa. A series of collecting trips to Chile to obtain cestodes from the yellownose skate, Dipturus chilensis , provided a unique opportunity to apply modern morphological and molecular methods to investigate the 3 species of Echeneibothrium reported parasitizing this skate, specifically Echeneibothrium megalosoma, Echeneibothrium multiloculatum, and Echeneibothrium williamsi. In addition to redescribing all 3 species, using morphological data from light and scanning electron microscopy, maximum likelihood and bayesian inference phylogenetic analyses of the D1-D3 regions of the 28S rDNA gene were conducted to assess their relationships among other echeneibothriids for which comparable data are available. Sequencing of 59 specimens representing these 3 species of Echeneibothrium allowed us to assess the intra- and interspecific variation in the 28S rDNA gene. The redescriptions use standardized terminology for scolex morphology, proglottid anatomy, and microthrix forms and pattern; they also expand on the original descriptions to include data on scolex size, ovary size, vas deferens and vaginal configurations, testes arrangement, and genital pore position. Our morphological work led to a major reinterpretation of the scolex morphology with the recognition that all 3 species bear an apical bothridial sucker, rather than an apical loculus, prompting emendation of the diagnosis for the family Echeneibothriidae. The presence of a band of spinitriches at the apex of the apical modification of the scolex proper seems to represent an important feature for distinguishing the 2 portions of the myzorhynchus across species. Intraspecific variation ranged from 0 to 7 bp across species and interspecific variation ranged from a low of 39-46 bp between E. williamsi and E. multiloculatum to a high of 61-66 bp between E. multiloculatum and E. megalosoma. Phylogenetic analyses indicate that the 3 species of Echeneibothrium hosted by the yellownose skate are not each other's closest relatives, suggesting multiple colonization events of D. chilensis have occurred. Further phylogenetic investigation is also likely to confirm the status of the genus Pseudanthobothrium as a synonym of Echeneibothrium because its species generally group among members of Echeneibothrium.

Prochristianella clarkeae Beveridge, 1990 (Eutetrarhynchidae): a species complex or a species with intraspecific variation in the distribution of its tegumental microtriches?

The microthrix pattern of common forms of the trypanorhynch cestode Prochristianella clarkeae Beveridge, 1990 on which the microscopically visible microtriches almost extended to the posterior end of the scolex was described using SEM and compared to other forms for which this pattern was different. The proximal bothrial surface and the scolex peduncle of all the examined specimens were covered with palmate spinitriches and papilliform filitriches. Unlike the common specimens of P. clarkeae, on the surface of those specimens with unusual distributions of microtriches as well as those on which the microscopically visible microtriches were not observable, palmate spinitriches extended to the mid-pars vaginalis and not to the posterior end of the scolex. Statistical tests did not detect any significant difference in the measurements of the specimens possessing different microthrix patterns. Furthermore, the partial 28S rDNA confirmed that the different forms were conspecific and that P. clarkeae possesses an intraspecific variation in the distribution of palmate spinitriches. Pastinachus sephen as a new host record was also established for Prochristianella clarkeae reported for the first time from the Persian Gulf.

A new genus of rhinebothriidean cestodes from batoid elasmobranchs, with the description of five new species and two new combinations

Survey work of batoid elasmobranchs in the eastern Atlantic and Indo-Pacific revealed multiple species of a new genus of cestode. Stillabothrium Healy et Reyda gen. n. (Rhinebothriidea: Escherbothriidae) is unique in its possession of an even number of non-medial longitudinal septa in the posterior portion of the bothridia, resulting in a series of loculi that are longer than wide (i.e. vertically oriented) and are arranged in columns. Five new species of Stillabothrium are described, S. ashleyae Willsey et Reyda sp. n., S. davidcynthiaorum Daigler et Reyda sp. n., S. campbelli Delgado, Dedrick et Reyda sp. n., S. hyphantoseptum Herzog, Bergman et Reyda sp. n., S. jeanfortiae Forti, Aprill et Reyda sp. n., and two species are formally transferred to the genus, S. amuletum (Butler, 1987) comb. n., and S. cadenati (Euzet, 1954) comb. n., the latter of which is redescribed. The species differ in the configuration of the other bothridial septa and in proglottid anatomy. Species of Stillabothrium were found parasitising a total of 17 species of batoid elasmobranchs of the genera Dasyatis Rafinesque, Glaucostegus Bonaparte, Himantura Müller et Henle, Pastinachus Rüppell, Rhinobatos Linck and Zanobatus Garman, including several host species that are likely new to science. A phylogenetic hypothesis based on Bayesian analysis of 1 084 aligned positions of the D1-D3 region of 28S rDNA for 27 specimens representing 10 species of Stillabothrium and two outgroup species supported the monophyly of Stillabothrium. These results also supported morphologically determined species boundaries in all cases in which more than one specimen of a putative species was included in the analysis. Host specificity appears to vary across species of Stillabothrium, with the number of host species parasitised by each species of Stillabothrium ranging from one to four. The geographic distribution of species of Stillabothrium spans the eastern Hemisphere, including the eastern Atlantic (coastal Senegal) and several locations in the Indo-Pacific (coastal Vietnam, Borneo and Australia). In addition, Phyllobothrium biacetabulatum Yamaguti, 1960 is formally transferred into family Escherbothriidae, although its generic placement remains uncertain (species incertae sedis).

Two new cestode species of Tetragonocephalum Shipley & Hornell, 1905 (Lecanicephalidea, Tetragonocephalidae) from Himantura randalli Last, Manjaji-Matsumoto & Moore (Myliobatiformes, Dasyatidae) from the Gulf of Oman

The original description of the genus Tetragonocephalum was published more than one hundred years ago but its taxonomic status was clarified only recently. To date, approximately 30 nominal species of this genus have been described, mostly from the northern Indian Ocean, but nearly half of them are invalid and only 14 species are recognized as valid. In the present study two new species of Tetragonocephalum are described from the spiral intestine of Himantura randalli from off Jod, on the northern coast of the Gulf of Oman. Tetragonocephalum sabaesp. n. is distinguishable from the valid species of Tetragonocephalum based on number of proglottids (43-53), number of testes (42-50), and size of scolex (401-453×328-455), acetabula (87-109×72-116), mature proglottids (802-1,333×226-336), cirrus sac (92-160×103-154), and eggs (16-19×11-13). Tetragonocephalum salariisp. n. can be distinguished from Tetragonocephalum sabaesp. n. and all other valid species of Tetragonocephalum based on number of proglottids (77-86). Furthermore, it differs from its congeners based on a combination of some characteristics, including the number of mature (3-7) and gravid (18-20) proglottids, the number of testes (30-38), and the size of acetabula (84-111×80-96), mature proglottids (497-833×334-403), gravid proglottids (1,036-1,482×440-575), testes (20-34×31-50), ovary (123-215×210-278), and eggs (24-45×13-21).

The occurrence of the common European fish cestode Caryophyllaeus laticeps (Pallas, 1781) in the River Irtysh, China: a morphological characterization and molecular data

The cestode Caryophyllaeus laticeps (Pallas, 1781) is a highly polymorphic species with several morphotypes, and belongs to the most widespread species of monozoic tapeworm (Cestoda: Caryophyllidea) found in the Palaearctic zoogeographic region with a wide range of cyprinid fish hosts. This paper provides the first reliable evidence about the occurrence of C. laticeps in northern China that is based on detailed morphological characteristics and mitochondrial cox1 sequences. C. laticeps was found in freshwater bream Abramis brama (L.), in the River Irtysh, with the prevalence of 40% and mean intensity of infection 8. The tapeworms were rather similar in their morphological characters to the morphotype 1 of C. laticeps which is typified by the possession of a slender body with a flabellate wide scolex, narrow neck, robust, long and clearly visible vas deferens, large, and almost spherical cirrus-sac containing well-developed internal seminal vesicle and the first vitelline follicles and first testes beginning far from anterior margin of the body. Subsequent molecular analysis confirmed the morphological identification of the species. Our results show that the studied specimens were firmly clustered into the C. laticeps clade and formed a monophyletic group with C. laticeps morphotype 1 and 2 from Europe and Russia. In China, C. laticeps is a non-indigenous fish parasite, which has the most probably been introduced into the Irtysh River basin with its typical host inhabiting Russia.

Prevalence and Scanning Electron Microscopic Identification of Anoplocephalid Cestodes among Small Ruminants in Senegal

This study was undertaken to determine the prevalence of anoplocephalid cestodes in sheep and goats in Senegal. Intestines of 462 sheep and 48 goats were examined; 47.4% of sheep and 6.2% of goats were infected. The species identified and their prevalence were, among sheep, Avitellina centripunctata 38.7%, Moniezia expansa 15.4%, Stilesia globipunctata 16.7%, and Thysaniezia ovilla 0.4%. Among goats, they were M. expansa 6.2% and T. ovilla 2.1%. The prevalence of all species was not statistically different between dry and rainy seasons. The infections were single or multiple. Indeed, 56.2% of sheep were infected by a single species, 37.4% by two species, and 6.4% by three species. For goats, 66.7% were infected by M. expansa and 33.3% by both M. expansa and T. ovilla. Scanning electron microscopic (SEM) observations of tapeworms show the general diagnosis characters of these species.

Review of the genus Shirleyrhynchus Beveridge & Campbell, 1988 (Trypanorhyncha: Shirleyrhynchidae), with the resurrection of S. butlerae Beveridge & Campbell, 1988 and the description of S. panamensis n. sp

A new species of trypanorhynch cestode is described from two species of stingrays, the Panamic stingray Urotrygon aspidura (Jordan & Gilbert) and the Pacific chupare Himantura pacifica (Beebe & Tee-Van) collected in the Golfo de Montijo in the Eastern Pacific Ocean off the coast of Panama. Shirleyrhynchus panamensis n. sp. represents an important addition to the family, which until now consisted of two monotypic genera. The new species is characterised by an elongate scolex with four, ovate bothria, presence of prebulbar organs, absence of gland cells within the muscular bulbs and an oncotaxy with a typical heteroacanthous, heteromorphous tentacular armature, a characteristic basal armature and the presence of a slight basal swelling. It is readily distinguished from its congeners by a smaller scolex and features of the oncotaxy, such as dissimilar hooks on opposing principle rows, a commencement of hook rows from the bothrial to the antibothrial surface and a much shorter basal armature. Although described only on the basis of immature worms lacking a strobila, the new species adds information on features of the oncotaxy within Shirleyrhynchus Beveridge & Campbell, 1988. Observation of the holotype of Shirleyrhynchus aetobatidis (Shipley & Hornell, 1906) revealed apparent differences from Australian specimens that have been described as Shirleyrhynchus butlerae Beveridge & Campbell, 1988 but which were later synonymised. Observations of type-specimens of S. butlerae also revealed differences from the original description and some morphological characteristics are amended. Shirleyrhynchus butlerae is herein resurrected and an amended generic diagnosis and a key to the identification of species are provided. The molecular voucher specimen of 'S. aetobatidis' utilised in previous molecular phylogenetic studies was re-observed which revealed a misidentification of the specimen with Parachristianella indonesiensis Palm, 2004.

A new species of Paraberrapex Jensen, 2001 (Cestoda: Lecanicephalidea) from Squatina guggenheim Marini (Squatiniformes: Squatinidae) off Argentina

Paraberrapex atlanticus sp. n. (Cestoda: Lecanicephalidea) is described from the spiral intestine of the angel shark Squatina guggenheim Marini from coastal waters off Buenos Aires Province, Argentina. Paraberrapex atlanticus sp. n. can be distinguished from the only species described in the genus, P. manifestus Jensen, 2001 in having cocoons 5-6 times longer with more eggs per cocoon, the extension of the uterine duct, the distribution of vitelline follicles, and the size and density of microtriches on the bothridial surfaces. The presence of P. atlanticus sp. n. in S. guggenheim confirms the specificity of Paraberrapex Jensen, 2001 for squatiniform sharks.

In Vitro Study of Taenia solium Postoncospheral Form

Background

The transitional period between the oncosphere and the cysticercus of Taenia solium is the postoncospheral (PO) form, which has not yet been completely characterized. The aim of this work was to standardize a method to obtain T. solium PO forms by in vitro cultivation. We studied the morphology of the PO form and compared the expression of antigenic proteins among the PO form, oncosphere, and cysticerci stages.

Methodology/Principal Findings

T. solium activated oncospheres were co-cultured with ten cell lines to obtain PO forms, which we studied at three stages of development–days 15, 30, and 60. A high percentage (32%) of PO forms was obtained using HCT-8 cells in comparison to the other cell lines. The morphology was observed by bright field, scanning, and transmission electron microscopy. Morphology of the PO form changed over time, with the six hooks commonly seen in the oncosphere stage disappearing in the PO forms, and vesicles and microtriches observed in the tegument. The PO forms grew as they aged, reaching a diameter of 2.5 mm at 60 days of culture. 15–30 day PO forms developed into mature cysticerci when inoculated into rats. Antigenic proteins expressed in the PO forms are also expressed by the oncosphere and cysticerci stages, with more cysticerci antigenic proteins expressed as the PO forms ages.

Conclusions/Significance

This is the first report of an in vitro production method of T. solium PO forms. The changes observed in protein expression may be useful in identifying new targets for vaccine development. In vitro culture of PO form will aid in understanding the host-parasite relationship, since the structural changes of the developing PO forms may reflect the parasite’s immunoprotective mechanisms. A wider application of this method could significantly reduce the use of animals, and thus the costs and time required for further experimental investigations.

Neurocysticercosis is caused by T. solium, which is a neglected disease. The postoncospheral (PO) form is an intermediate form between the oncosphere, which is the larva, and the fully developed cysticercus, which is a cyst with a scolex. The morphology, development, and protein and antigen expression of the PO form have not previously been characterized. Here, we report the novel in vitro cultivation of T. solium PO forms and characterize the morphology, development, and expression of antigenic proteins. This new method will allow for better study of this transitional form, which is very difficult to study in the intermediate host. With the increased availability of secreted proteins and antigens, in vitro cultivation will help improve diagnostic assays and provide new targets for vaccine development to block transmission.

Diversity, phylogenetic relationships and host associations of Calliobothrium and Symcallio (Cestoda: ‘Tetraphyllidea') parasitising triakid sharks

The laciniate, relatively large-bodied tetraphyllidean tapeworm genus Calliobothrium van Beneden, 1850 parasitises triakid sharks with all but one species found parasitising sharks of the genus Mustelus Linck, 1790. Historically, species of this genus were thought to exhibit a relaxed degree of host specificity relative to species of their sister genus Symcallio Bernot, Caira, & Pickering, 2015. However, several more recent studies have begun to question this difference and, in particular, the conspecificity of specimens identified as the types species, C. verticillatum (Rudolphi, 1819) van Beneden, 1850, from multiple host species. Our results suggest that diversity in the genus Calliobothrium has been under-reported. To explore this situation, specimens previously identified as C. verticillatum were collected from Mustelus asterias Cloquet, 1819 off the United Kingdom and Mustelus canis (Mitchell, 1815) off Connecticut, USA; these sharks each were found to host distinct species both of which are described here. Mustelus asterias was also confirmed to host Symcallio leuckarti (van Beneden, 1850) Bernot, Caira & Pickering, 2015, which is redescribed. In combination with newly collected material from Mustelus palumbes Smith, 1957 off South Africa and data available from GenBank, molecular phylogenetic analyses based on 28S rDNA data for four of the seven known species of Calliobothrium, including both new species and five of the 11 known species of Symcallio, were conducted. The resulting phylogeny supports the mutual monophyly of the two genera, which are readily distinguished based on whether they exhibit proglottid laciniations, and supports subclades of Symcallio with and without hook accessory pieces. These subclades of Symcallio appear to exhibit an intriguing congruence with two known subclades of their host genus, Mustelus.

Microthrix pattern of Pseudogilquinia thomasi (Palm, 2000) (Cestoda: Trypanorhyncha) and a review of surface ultrastructure within the family Lacistorhynchidae Guiart, 1927

The microthrix pattern of larvae of Pseudogilquinia thomasi (Palm, 2000) is described for the first time using scanning electron microscopy. The surface ultrastructure of this species consists of three main forms of microtriches: papilliform filitriches, acicular filitriches and quadridigitate to octadigitate palmate spinitriches. The bothria are covered with palmate spinitriches interspersed on some parts with papilliform filitriches. Palmate spinitriches with papilliform, acicular and capilliform filitriches adorn the pars vaginalis and at the anterior part of the pars bulbosa, there is a transition zone in which the palmate spinitriches are replaced by papilliform to acicular filitriches towards the end of the scolex. ANOVA tests with Duncan's post hoc analyses revealed that there are significant differences in the length of spinitriches and their prongs, whether on the surfaces of the bothria or on the surfaces of the scolex peduncle. Callitetrarhynchus gracilis Pintner, 1931 is the second lacistorhynchid species for which surfaces of the segments were examined and the occurrence of large structures called scutes are reported for the first time from this species. There were also significant differences in the base length as well as height of the scutes in different parts of the strobila. In addition to describing the surface ultrastructures of the two lacistorhynchid species, all the available information on the microtriches within the family Lacistorhynchidae is reviewed herein and generic diagnoses related to microtriches are amended.

Surface ultrastructure and the mitochondrial gene rrnl of Parachristianella indonesiensis Palm, 2004 (Trypanorhyncha: Eutetrarhynchidae) with the amended generic diagnosis

The microthrix pattern of adult Parachristianella indonesiensis Palm, 2004 is described for the first time based on the standardized terminology for microtriches, and the generic diagnosis of Parachristianella Dollfus, 1946, regarding microtriches, is also amended. The surface ultrastructure of P. indonesiensis consists of three kinds of microtriches so that the proximal and distal bothrial surfaces are covered respectively with acicular to short capilliform filitriches and aristate gladiate spinitriches interspersed with capilliform filitriches. The remainder of the scolex bears capilliform filitriches. The surface of the proglottid is adorned with acicular filitriches. There was no significant difference in the length of the capilliform filitriches covering the different parts of the scolex peduncle. For the first time, the uniciliated papillae adorned with filitriches as sensory receptors are reported from this parasitic species. The partial rrnl of P. indonesiensis is also presented as the only known sequence of this gene in the superfamily Eutetrarhynchoidea Dollfus, 1969. The pairwise comparisons of rrnl between P. indonesiensis and the trypanorhynch species for which rrnl sequence is available were in accordance with the last phylogeny presented for the order Trypanorhyncha. The infection parameters (prevalence, mean abundance, and mean intensity) of P. indonesiensis parasitizing Pastinachus sephen (Forsskål) from the eastern Persian Gulf were also compared during approximately 5 years, and no significant differences were observed. This may be interpreted as the stability of the factors playing important roles in the life cycle of P. indonesiensis in the eastern Persian Gulf during this period.

Trypanorhynch cestodes (Eutetrarhynchidae) from batoids along the coast of Argentina, including the description of new species in Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974

During a recent parasitological survey of elasmobranchs along the coast of Argentina, two new species of eutetrarhynchid cestodes of the genera Dollfusiella Campbell et Beveridge, 1994 and Mecistobothrium Heinz et Dailey, 1974 were collected from batoids. Dollfusiella acuta sp. n. was found in four arhynchobatid skates, i.e. Sympterygia acuta Garman (type host), Sympterygia bonapartii Müller et Henle, Atlantoraja castelnaui (Miranda Ribeiro) and Atlantoraja platana (Günther), and Mecistobothrium oblongum sp. n. in the eagle ray Myliobatis goodei Garman. Dollfusiella acuta sp. n. has a tentacular armature consisting of basal rows of uncinate hooks, a distinct basal swelling with uncinate, falcate and bill hooks, and a heteroacanthous metabasal armature with heteromorphous hooks (bothrial uncinate hooks and antibothrial falcate hooks), hooks 1(1') not separated, testes in two columns and an internal seminal vesicle. The tentacular armature of M. oblongum sp. n. is characterised by basal rows of uncinate hooks, a basal swelling with uncinate and falcate hooks, a typical heteroacanthous metabasal armature with heteromorphous hooks (uncinate and falcate to spiniform), and hooks 1(1') separated and of a constant size along the tentacle. It also possesses an elongate scolex, numerous testes arranged in 5-6 irregular columns, and an internal seminal vesicle. The discovery of M. oblongum in M. goodei represents the first record of species of Mecistobothrium in the southwestern Atlantic Ocean. An amended description of Dollfusiella cortezensis (Friggens et Duszynski, 2005) is also provided to clarify details of the scolex and tentacular armature. Members of Dollfusiella in the southwestern Atlantic are specific to a single host species or to a particular host family, while M. oblongum was found in a single host species. Although globally some plerocerci of eutetrarhynchids have been found in teleosts, extensive examination of teleosts off the coast of Argentina suggests that the transmission pathways of these species are exclusively based on invertebrates as intermediate or paratenic hosts.

High morphological plasticity and global geographical distribution of the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum): molecular and morphological survey

The most important causative agent of human diphyllobothriosis in South America, Diphyllobothrium pacificum, is transferred to the original genus Adenocephalus Nybelin, 1931; revised and redescribed on the basis of the evaluation of an extensive material collected mainly from northern fur seal, Callorhinus ursinus, from St. Paul Island, Alaska. Detailed analysis of morphological and morphometrical data shows a high variability in most of the characteristics traditionally used in diagnosis of diphyllobothriid tapeworms. Phylogenetic analyses based on newly characterised sequences of mitochondrial cytochrome c oxidase subunit 1 and nuclear large subunit ribosomal RNA genes consistently reveal Adenocephalus pacificus as a sister lineage to the clade formed of the remaining Diphyllobothrium species and other genera (Digramma, Diplogonoporus, Ligula). Despite the generally similar morphology, A. pacificus can be differentiated from the closely related taxa in the presence of transverse papilla-like tegumental protuberances distributed anteriorly, separated by narrow semicircular grooves on the ventral surface of proglottids between their anterior margin and the anterior edge of the male gonopore, and relatively small eggs. A. pacificus displays a relatively low host specificity (found in 9 of 16 otariids, and in accidental hosts such as man, dog and jackal, the latter representing a new host) and a uniquely wide geographical distribution on both hemispheres. In addition, suitability of morphological criteria used in diagnostics of diphyllobothriid cestodes is discussed.

Two new species of Rhinebothrium (Cestoda: Rhinebothriidea) from granulated guitarfish Glaucostegusgranulatus in the Gulf of Oman

During a study of the rhinebothriideans of rays in the Gulf of Oman, two new species of Rhinebothrium Linton, 1890, Rhinebothrium kruppi sp. n. and R. persicum sp. n., were identified in Glaucostegus granulatus (Cuvier). Some significant features that distinguish R.kruppi sp. n. from R. persicum sp. n. include: scolex characteristics (hinged with 42–46 loculi vs. fusiform with 68–62 loculi), number of testes (4–5 vs. 20–27), genital pore position (61.1–76.9% of proglottid length vs. 47.2–63.3%), ovarian morphology (lobulated vs. follicular), cirrus-sac expansion (past midline of proglottid vs. limited to poral side of proglottid), vas deferens configuration (spanning posteriorly to near ovarian isthmus vs. to the level of ovarian anterior margins) and details of microthrix morphology. In addition, a combination of the aforementioned characteristics can be used to distinguish these two new species from other valid species of Rhinebothrium. These are the first species of rhinebothriidean cestodes to be described systematically from the Gulf of Oman, Iran. The two new species reported here increase the number of valid species of Rhinebothrium to 43.

Morphological and molecular characterisation of Ditrachybothridium macrocephalum Rees, 1959 (Cestoda: Diphyllidea) from Galeus melastomus Rafinesque in the Western Mediterranean

New morphological, molecular and ecological data for Ditrachybothridium macrocephalum Rees, 1959 (Cestoda: Diphyllidea) are presented and discussed based on specimens recovered from the blackmouth catshark Galeus melastomus Rafinesque (Scyliorhinidae) in the Western Mediterranean. A redescription of the plerocercus of this parasite is provided and new data on immature and mature worms including the first description of the eggs are reported, based on light and scanning electron microscopy observations. Analysis of 28S rDNA (domains D1-D3) sequences from plerocerci, immature and adult specimens revealed that they are conspecific with specimens from the North East Atlantic. Although previous authors considered that museum specimens identified as D. macrocephalum may represent more than one species, examination of type- and voucher material revealed no relevant morphological differences between museum specimens and the present material. Information on infection levels of D. macrocephalum is provided from a large number of host specimens (n = 170). This species was more abundant in juvenile than in adult hosts and on the middle slope than on the upper slope; this may be related to ontogenetic and bathymetric diet shifts of G. melastomus.

Ultrastructure of the anterior organ and posterior funnel-shaped canal of Gyrocotyle urna Wagener, 1852 (Cestoda: Gyrocotylidea)

Using scanning and transmission electron microscopy, ultrastructure of the anterior organ and posterior funnel-shaped canal of Gyrocotyle urna Wagener, 1852 (Cestoda: Gyrocotylidea) from ratfish, Chimaera monstrosa (Holocephali), was studied for the first time. The proper anterior organ is localised at a short distance (about 170 µm) from an apical pore surrounded by a receptor field, whereas its distal end is marked by a muscular sphincter. The tegumental surface of this organ is covered with short filitriches of irregular length; large area of muscle layers traverse beneath the tegumental layer. The funnel-shaped canal of G. urna (2.5-3.0 mm long) is a specialised, muscular part of the posterior attachment organ; it opens on the rounded elevation on the dorsal body surface. The tegumental layer bears conical sclerite-like structures (up to 1.5 µm long). It produces electron-dense bodies that are transported into a canal lumen and surrounded thick muscle area mixed with numerous nerve fibres. The present ultrastructural study of G. urna indicates that gyrocotylideans share some ultrastructural characters of the anterior organ with spathebothriidean cestodes with a single anterior attachment sucker-like organ. In contrast, the unique posterior rosette attachment organ with funnel-shaped canal of the Gyrocotylidea resembles the haptor of polyopisthocotylean monogeneans in its position at the posterior end of the body and presumed origin. The above-mentioned features add more clarity to support the basal position of the Gyrocotylidea Poche, 1926 among cestodes. In addition, they also indicate a possible relationship of gyrocotylidean ancestors with monogeneans.

A large 28S rDNA-based phylogeny confirms the limitations of established morphological characters for classification of proteocephalidean tapeworms (Platyhelminthes, Cestoda)

Proteocephalidean tapeworms form a diverse group of parasites currently known from 315 valid species. Most of the diversity of adult proteocephalideans can be found in freshwater fishes (predominantly catfishes), a large proportion infects reptiles, but only a few infect amphibians, and a single species has been found to parasitize possums. Although they have a cosmopolitan distribution, a large proportion of taxa are exclusively found in South America. We analyzed the largest proteocephalidean cestode molecular dataset to date comprising more than 100 species (30 new), including representatives from 54 genera (80%) and all subfamilies, thus significantly improving upon previous works to develop a molecular phylogeny for the group. The Old World origin of proteocephalideans is confirmed, with their more recent expansion in South America. The earliest diverging lineages are composed of Acanthotaeniinae and Gangesiinae but most of the presently recognized subfamilies (and genera) appear not to be monophyletic; a deep systematic reorganization of the order is thus needed and the present subfamilial system should be abandoned. The main characters on which the classical systematics of the group has been built, such as scolex morphology or relative position of genital organs in relation to the longitudinal musculature, are of limited value, as demonstrated by the very weak support for morphologically-defined subfamilies. However, new characters, such as the pattern of uterus development, relative ovary size, and egg structure have been identified, which may be useful in defining phylogenetically well-supported subgroups. A strongly supported lineage infecting various snakes from a wide geographical distribution was found. Although several improvements over previous works regarding phylogenetic resolution and taxon coverage were achieved in this study, the major polytomy in our tree, composed largely of siluriform parasites from the Neotropics, remained unresolved and possibly reflects a rapid radiation. The genus Spasskyellina Freze, 1965 is resurrected for three species of Monticellia bearing spinitriches on the margins of their suckers.

An annotated list of the species of Gangesia Woodland, 1924 (Cestoda: Proteocephalidea), parasites of catfishes in Asia, with new synonyms and a key to their identification

An annotated list of tapeworms of the genus Gangesia Woodland, 1924 (Cestoda: Proteocephalidea), parasites of siluriform fishes in Asia, is provided. Based on the morphological examination of museum specimens and newly collected material from China, Japan and Russia, as well as the results of a previous revision of the Indomalayan species, only eight of more than 50 nominal taxa are considered to be valid. These are: from India and neighbouring countries, Gangesia bengalensis (Southwell, 1913) (type-species), G. agraensis Verma, 1928, both from Wallago attu (Bloch & Schneider) (Siluridae), G. macrones Woodland, 1924 from Sperata seenghala (Sykes) (Bagridae) and G. vachai (Gupta & Parmar, 1988) from different catfishes (type-host Eutropiichthys vacha (Hamilton); Schilbeidae), and, from the Palaearctic, G. margolisi Shimazu, 1994, a parasite of Silurus biwaensis (Tomoda) (Siluridae) in Japan, G. oligonchis Roitman & Freze, 1964 from Tachysurus fulvidraco (Richardson) (Bagridae) in Russia, and G. parasiluri Yamaguti, 1934 and G. polyonchis Roitman & Freze, 1964, both from Silurus asotus L. (Siluridae) in Japan and Russia, respectively. The poorly known G. oligonchis is redescribed. Seven new synonyms are proposed: G. chauhani Mathur & Srivastav, 2000, G. wallaguae Pradhan, Kulkarni, Kale & Wakle, 2010 and G. shivajiraoi Dhole, Waghmare & Chavan, 2012 are synonymised with G. agraensis; G. striatusii Bhure & Nanaware, 2012 and Silurotaenia govindii Sawarkar, 2013 with G. macrones; G. spasskajae Demshin, 1987 with G. polyonchis; and Silurotaenia spinula Chen, 1984 with Postgangesia orientalis Akhmerov, 1969. Gangesia pseudobagrae Chen, 1962 is considered to be a species inquirenda, whereas G. chauhani Mathur, 1992 and G. dineshei Jaysingpure, 2002 are recognised as unavailable names. An amended generic diagnosis of Gangesia and a key to the identification of its recognised species are also provided.

Asian fish tapeworm, Khawia japonensis (Yamaguti, 1934), has expanded its European invasive range

The invasive fish tapeworm, Khawia japonensis (Yamaguti, 1934) originally described in Japan, is reported for the first time in Slovakia. The tapeworm was found in farmed common carp (Cyprinus carpio L.) from East-Slovakian breeding fish pond. This finding is registered 4 years after the first announcement of this parasite in Europe (Po River Basin in Italy) in 2010 and increases its distribution area within this continent. Morphological characterization of K. japonensis supplemented with DNA sequences of cox1 and ribosomal lsrDNA genes is provided. Specimens from Slovakia phenotypically corresponded with those from feral and farmed carps from China, Vietnam, and Italy. Moreover, 100 and 98.7% identity of partial ribosomal lsrDNA gene and mitochondrial cox1 genes, respectively, were detected with K. japonensis from Japan. The invasive and pathogenic potential of K. japonensis in commercial breeding fisheries and its possible further spread in natural habitats is difficult to estimate for now. As yet, K. japonensis appears to be without a major impact on commercial breeding fisheries, but calls for more attention to the problem of biological invasions.

A new species of Bothriocephalus Rudolphi, 1808 (Eucestoda: Bothriocephalidea) from the channel bull blenny Cottoperca gobio (Günther) (Perciformes: Bovichtidae) on the Patagonian shelf off Argentina

Bothriocephalus timii n. sp. is the first tapeworm species reported from a bovichtid fish. The new species was commonly found (prevalence 85%) in the intestine of Cottoperca gobio (Günther) collected on the Patagonian shelf off Argentina. It is characterised by a strobila with segments and proglottides usually longer than wide, having posterolateral wing-like expansions with a medial notch on both the dorsal and ventral surfaces; a scolex with an apical disk; elongate bothria opening posteriorly, with laterally and longitudinally extended convex lappets; testes 42-185 in number, in one layer, arranged in two lateral continuous bands along the strobila; an elongate cirrus-sac, situated obliquely, with the proximal part curved anteriolaterally; and an ovary which is usually butterfly-shaped. The new species is morphologically similar to B. bengalensis Devi, 1975 from Carangoides plagiotaeniata Bleeker, B. branchiostegi Yamaguti, 1952 from Branchiostegus japonicus Houttuyn, B. carangis Yamaguti, 1968 from C. ferdau Forsskål and B. gadellus Blend & Dronen, 2003 from Gadella imberbis (Vaillant) based on the presence of posterolateral wing-like expansions with a medial notch on dorsal and ventral surfaces of segments and proglottides along the strobila. Bothriocephalus timii n. sp. differs from B. bengalensis, B. branchiostegi and B. carangis in the absence of a vaginal sphincter and from B. gadellus in the number of testes and the size of scolex. Unpublished molecular data suggest that B. timii is most closely related to B. australis Kuchta, Scholz & Justine, 2009 from Platycephalus spp. and B. scorpii (Müller, 1776) from Myoxocephalus scorpius (Linnaeus). The genus Indobothrium Sedova & Gulyaev, 2009 is herein considered a junior synonym of Bothriocephalus Rudolphi, 1808.

A new genus and species of proteocephalidean tapeworm (Cestoda), first parasite found in the driftwood catfish Tocantinsia piresi (Siluriformes: Auchenipteridae) from Brazil

Frezella gen. n. is proposed to accommodate Frezella vaucheri sp. n. from poorly known auchenipterid fish, Tocantinsia piresi (Miranda Ribeiro), from the Xingú River, one of the principal tributaries of the lower Amazon River in Brazil. The new genus belongs to the Proteocephalinae because of the medullary position of the testes, ovary (yet some follicles penetrate to the cortex on the dorsal side), vitelline follicles and uterus. It differs from other proteocephaline genera in the morphology of the scolex, which includes a metascolex composed of two distinct zones: anterior, strongly wrinkled part posterior to the suckers, and posterior, sparsely folded zone. Frezella can also be differentiated by having the internal longitudinal musculature hypertrophied laterally on both sides, the presence of some ovarian follicles in the cortex on the dorsal side and the presence of additional pair of tiny, thin-walled osmoregulatory canals situated slightly dorsomedian to ventral canals. Frezella vaucheri is the first helminth parasite reported from T. piresi, which occurs in the lower reaches of the Amazon and Tocantins River basins in Brazil.

A new genus and two new species of lecanicephalidean tapeworms from the striped panray, Zanobatus schoenleinii (Rhinopristiformes: Zanobatidae), off Senegal

Recognised for their diversity in apical structure morphology, members of the cestode order Lecanicephalidea Wardle et McLeod, 1952 known to date exhibit relatively mundane and uniform acetabular morphology. A new lecanicephalidean genus, Zanobatocestus gen. n., is proposed for two new species found parasitising the spiral intestine of the striped panray, Zanobatus schoenleinii (Müller et Henle), off Senegal that are highly unusual in acetabular morphology. Unlike the members of the 21 recognised lecanicephalidean genera, which possess simple, uniloculate suckers or bothridia, Zanobatocestus minor sp. n. and Z. major sp. n. possess biloculate bothridia. The form of their apical structures and cocoons readily distinguish the two new species from one another. Zanobatocestus minor sp. n. exhibits an apical modification of the scolex proper that is narrow and elongated, an apical organ that is small and internal, and eggs in cocoons forming linear strands, whereas Z. major sp. n. exhibits an apical modification of the scolex proper that is wide and short, an apical organ that is extensive and primarily external, and eggs in cocoons primarily as doublets with bipolar filaments. Given the typically high host specificity of lecanicephalidean cestodes, as parasites of the only genus and species currently considered valid in the family Zanobatidae, Zanobatocestus gen. n. is likely to remain one of the less specious lecanicephalidean genera.

The dismantling of Calliobothrium (Cestoda: Tetraphyllidea) with erection of Symcallio n. gen. and description of two new species

This paper aims to resolve the dual composition of the triakid shark-hosted tetraphyllidean genus Calliobothrium--an issue that has been recognized for over a decade. As it stands, this genus includes a number of large species with laciniate proglottids, most of which bear 3 suckers at the anterior margin of each bothridium, but it also includes a number of species that lack proglottid laciniations and bear only a single sucker per bothridium, most of which are relatively small. Discovery of 2 new species, 1 of each form, parasitizing the whitespot smoothhound shark, Mustelus palumbes, off South Africa, prompted the first molecular analysis of the genus. Bayesian inference and maximum likelihood analyses of 28S rDNA (D1-D3) sequence data generated for specimens of both new species as well as of 2 known species of the laciniate form (Calliobothrium australis and Calliobothrium cf. verticillatum) and 3 known species of the non-laciniate form (Calliobothrium violae, Calliobothrium riseri, and Calliobothrium barbarae) confirmed the reciprocal monophyly of the 2 clades, supporting establishment of a new genus. Because the type of Calliobothrium, C. verticillatum, is of the laciniate form, Symcallio n. gen., with Symcallio peteri n. gen., n. sp., from M. palumbes described as its type, is established to house members of the non-laciniate clade. The 11 described species consistent with this form are transferred to the new genus. A new species of the laciniate clade, Calliobothrium euzeti n. sp., is described from M. palumbes, and a revised diagnosis of Calliobothrium is presented.

Morphology meets molecules: a new genus and two new species of diphyllidean cestodes from the Yellowspotted skate, Leucoraja wallacei, from South Africa

Two morphologically disparate undescribed species of diphyllidean cestodes from the Yellowspotted skate, Leucoraja wallacei , from South Africa were included in a recent molecular phylogenetic study aimed at revising diphyllidean classification. From a molecular standpoint, these species were determined to be only distantly related to one another. One (originally referred to as Echinobothrium n. sp. 2) showed affinities with species of the batoid-parasitizing Echinobothrium sensu stricto and is described here as Echinobothrium marquesi n. sp. This species most closely resembles Echinobothrium joshuai, an affinity supported by the previous molecular study, but differs in the form of its "B" hooks and degree of overlap between bothria and cephalic peduncle. The other species (originally referred to as New genus n. sp. 1), although exhibiting the full complement of scolex armature, grouped among primarily shark-hosted genera, most of which lack or exhibit reduced scolex armatures. That unexpected result suggested that erection of a novel genus might be warranted, but morphological grounds supporting the action were not apparent at that time. The present study aimed to explore the morphology of this taxon in more detail. Light and scanning electron microscopy revealed this taxon to be exceptional in that its lateral hooklets, which are arranged in 2 clusters like those of Echinobothrium and Coronocestus, are unique in being arranged in anterior and posterior rows, rather than in a single row. Andocadoncum n. gen. is erected, with Andocadoncum meganae n. sp. as its type, to accommodate this taxon. A minor adjustment to the existing hook formula by presenting counts for the anterior hooklets (a) separately from the posterior hooklets (b) readily accommodates this new form. Leucoraja wallacei is distinctive among skates in hosting 2 different genera of diphyllideans. In the context of the previous molecular phylogenetic analyses, it appears that the presence of Andocadoncum n. gen. in this skate species may be the result of a host-switching event involving a weakly or unarmed shark-hosted taxon moving to a batoid-a shift that was likely accompanied by a return to the fully armed condition seen, for example, in other batoid-parasitizing members of the order.

An enigmatic new tapeworm, Litobothrium aenigmaticum, sp. nov. (Platyhelminthes : Cestoda : Litobothriidea), from the pelagic thresher shark with comments on development of known Litobothrium species

An enigmatic new tapeworm is described from pelagic thresher sharks in México and Taiwan. While lsrRNA (D1-D3) data robustly place it in the Litobothriidea, it bears essentially no morphological resemblance to other members of the order. Instead it superficially resembles the freshwater fish-inhabiting Caryophyllidea. Its scolex consists of a simple dome-shaped scolex proper and an extensive cephalic peduncle housing four distinct tissue types. It is hyperapolytic, thus reproductive anatomy is unknown. Developmental data show typical litobothriideans bear basic elements of their adult scolex upon entering the definitive host, undermining the notion that the new cestode represents a distinct litobothriidean life cycle stage. Scanning electron microscopy revealed the new species shares bands of distinctive microtriches with its congeners. In combination these data justify establishment of Litobothrium aenigmaticum, sp. nov.; the generic, familial and ordinal diagnoses are emended accordingly. Unlike typical litobothriideans, each worm is associated with a mucosal expansion at its attachment site, like those seen in some caryophyllideans. This pathological change may represent a worm-induced host response serving to reinforce attachment of the simple scolex to the mucosa. If so, the convergence of this litobothriidean on a morphology like that seen in the distantly related Caryophyllidea is a result of similarity in mode of attachment.

Classification of the acanthocephala

In 1985, Amin presented a new system for the classification of the Acanthocephala in Crompton and Nickol's (1985) book 'Biology of the Acanthocephala' and recognized the concepts of Meyer (1931, 1932, 1933) and Van Cleave (1936, 1941, 1947, 1948, 1949, 1951, 1952). This system became the standard for the taxonomy of this group and remains so to date. Many changes have taken place and many new genera and species, as well as higher taxa, have been described since. An updated version of the 1985 scheme incorporating new concepts in molecular taxonomy, gene sequencing and phylogenetic studies is presented. The hierarchy has undergone a total face lift with Amin's (1987) addition of a new class, Polyacanthocephala (and a new order and family) to remove inconsistencies in the class Palaeacanthocephala. Amin and Ha (2008) added a third order (and a new family) to the Palaeacanthocephala, Heteramorphida, which combines features from the palaeacanthocephalan families Polymorphidae and Heteracanthocephalidae. Other families and subfamilies have been added but some have been eliminated, e.g. the three subfamilies of Arythmacanthidae: Arhythmacanthinae Yamaguti, 1935; Neoacanthocephaloidinae Golvan, 1960; and Paracanthocephaloidinae Golvan, 1969. Amin (1985) listed 22 families, 122 genera and 903 species (4, 4 and 14 families; 13, 28 and 81 genera; 167, 167 and 569 species in Archiacanthocephala, Eoacanthocephala and Palaeacanthocephala, respectively). The number of taxa listed in the present treatment is 26 families (18% increase), 157 genera (29%), and 1298 species (44%) (4, 4 and 16; 18, 29 and 106; 189, 255 and 845, in the same order), which also includes 1 family, 1 genus and 4 species in the class Polyacanthocephala Amin, 1987, and 3 genera and 5 species in the fossil family Zhijinitidae.