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Acanthobothrium ningdense n. sp. and Acanthobothrium guanghaiense n. sp. are described from the spiral intestine of the whip stingray, Dasyatis akajei (Müller & Henle). Acanthobothrium ningdense n. sp. is reported based on 38 cestode specimens collected at five locations along the Chinese coast, i.e. Taizhou, Zhejiang Province, Ningde and Xiamen, Fujian Province, Taishan, Guangdong Province and Sanya, Hainan Province between 2012 and 2015. Acanthobothrium ningdense n. sp. belongs to the "species category 4" characterised by Ghoshroy & Caira. Among category 4 Acanthobothrium species, A. ningdense n. sp. most closely resembles A. micracantha Yamaguti, 1952 and A. latum Yamaguti, 1952, both from the same host species. Acanthobothrium ningdense n. sp. differs from A. micracantha by lacking a long robust hook handle that connects the bases of medial and lateral hooks, and from A. latum by having much longer axial prongs than abaxial prongs. Acanthobothrium guanghaiense n. sp., only found in Taishan, Guangdong Province in 2014, is a category 2 Acanthobothrium species. Among category 2, A. guanghaiense n. sp. most closely resembles A. semnovesiculum Verma, 1928, but can be differentiated from it by the arrangement of testes (in two staggered columns rather than in two tandem columns), and the shape of abaxial prong (nearly straight instead of with a conspicuous curve in the proximal portion). Acanthobothrium macrocephalum Wang & Yang, 2001 is redescribed based on new specimens collected from D. akajei in Guanghai and Sanya. With this study, the total number of Acanthobothrium species reported from D. akajei is brought to nine. It is possible that some of the species of Acanthobothrium previously reported from D. akajei not encountered in this study may have geographically restricted distributions, as was observed here for A. guanghaiense n. sp..

Acanthocotyle urolophi sp. nov. is described from the skin of the banded stingaree, Urolophus cruciatus (Lacépède, 1804). This is the first acanthocotylid to be described from Australian waters. Acanthocotyle urolophi sp. nov. is distinguished from other species of Acanthocotyle by a combination of the number of vitelline follicles 38 (33-46) and the number of rows 35 (32-37) of sclerites on the pseudohaptor. In addition, Acanthocotyle urolophi sp. nov. has no germarial appendix and no uterine "arm". A uterine receptaculum seminis was not identified in whole mounts. There is no penis papilla and no penis sclerite associated with the male reproductive opening. A brief description of the larva is provided. The diagnosis of the Acanthocotylidae Price, 1936 is amended and we review the Allacanthocotylinae Yamaguti, 1963, Lophocotylinae Yamaguti, 1963 and Pseudacanthocotylinae Yamaguti, 1963. We deem that these subfamilies are invalid and that the family now comprises only the subfamily Acanthocotylinae and the genus Acanthocotyle. The validity of species previously assigned to the Acanthocotylidae (sensu Yamaguti, 1963) is discussed and a key to what we consider to be the valid species in the family is also provided.

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.

The present study uses scanning and transmission electron microscopical observations to examine the haptoral features of the hexabothriid polyopisthocotylean monogenean Rajonchocotyle emarginata from the gills of the elasmobranch Amblyraja radiata. The haptor possesses six equal, pedunculate suckers, each armed with a large, curved, hooked sclerite, and an appendix bearing two small, terminal suckers and a pair of minute hamuli. The outer side of the distal region of the hooked sclerite forms a large bulge along the antero-lateral side of each sucker and the proximal region forms a small bulge on the opposite postero-lateral side; part of the large bulge, which covers the small sclerite hook, surmounts the sucker rim. The sucker sclerite is situated outside the main sucker muscle complex of the sucker wall and is surrounded by its own muscular envelope; close to the sclerite itself, long, tightly packed lamella-like processes of sarcoplasm are present. A muscular sphincter surrounds the distal region of the sclerite shaft. The sclerite consists of three heterogeneous layers, but its hook region is distinguished from the shaft by the presence of an additional homogeneous layer. Hamuli within the appendix consist of three distinct layers loosely surrounded by sarcoplasmic lamellae. The luminal surface of the appendicular suckers is covered with unusual, long, thin, interconnected surface protrusions. In all other regions of the haptor, the tegumental surface is smooth, with numerous shallow pores penetrating the "terminal web" of the syncytial cytoplasm. Unicellular gland cells are localized close to the base of the appendix, with their ducts, containing non-homogenous secretory bodies, opening onto the anterior haptoral surface. Two types of sense receptors are visible on the haptoral surface. The ultrastructural features of the haptor are discussed in relation to our understanding of their function and the evolutionary relationships of the basal polyopisthocotylean monogenean groups Hexabothriidae and Chimaericolidae.

This study presents the first comprehensive phylogenetic analysis of the interrelationships of the morphologically diverse elasmobranch-hosted tapeworm order Lecanicephalidea, based on molecular sequence data. With almost half of current generic diversity having been erected or resurrected within the last decade, an apparent conflict between scolex morphology and proglottid anatomy has hampered the assignment of many of these genera to families. Maximum likelihood and Bayesian analyses of two nuclear markers (D1-D3 of lsrDNA and complete ssrDNA) and two mitochondrial markers (partial rrnL and partial cox1) for 61 lecanicephalidean species representing 22 of the 25 valid genera were conducted; new sequence data were generated for 43 species and 11 genera, including three undescribed genera. The monophyly of the order was confirmed in all but the analyses based on cox1 data alone. Sesquipedalapex placed among species of Anteropora and was thus synonymized with the latter genus. Based on analyses of the concatenated dataset, eight major groups emerged which are herein formally recognised at the familial level. Existing family names (i.e., Lecanicephalidae, Polypocephalidae, Tetragonocephalidae, and Cephalobothriidae) are maintained for four of the eight clades, and new families are proposed for the remaining four groups (Aberrapecidae n. fam., Eniochobothriidae n. fam., Paraberrapecidae n. fam., and Zanobatocestidae n. fam.). The four new families and the Tetragonocephalidae are monogeneric, while the Cephalobothriidae, Lecanicephalidae and Polypocephalidae comprise seven, eight and four genera, respectively. As a result of their unusual morphologies, the three genera not included here (i.e., Corrugatocephalum, Healyum and Quadcuspibothrium) are considered incertae sedis within the order until their familial affinities can be examined in more detail. All eight families are newly circumscribed based on morphological features and a key to the families is provided. Aspects of morphological evolution and host associations are discussed in a phylogenetic context for each family and for the order as a whole. Lecanicephalidean genera lacking apical structures were confirmed as the earliest diverging lineages. Proglottid anatomy was determined to be much more conserved and indicative of phylogenetic affinities than scolex morphology. Collectively, the Lecanicephalidea parasitize three of the four orders of Batoidea-their almost exclusive absence from skates (Order Rajiformes) appears to be real; only a few records from sharks exist. At the family level, the breadth of host associations is correlated with taxonomic diversity of the family. The degree to which factors such as intermediate host use or host specificity at any stage in the life-cycle shape these patterns is currently unknown., (Copyright © 2016 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.)

Dendromonocotyle rajidicola n. sp. is described from the dorsal surface of the yellownose skate Zearaja chilensis (Guichenot) (Rajiformes) caught on the Argentine shelf. Dendromonocotyle rajidicola n. sp. can be distinguished from the other 17 species in the genus by the morphology of the distal portion of the male copulatory organ and by the unique morphology of the sclerotised proximal portion of the vagina. This is the first species of Dendromonocotyle to be described from a host in the Rajiformes and also the first record of this genus in the southwestern Atlantic Ocean.

The genus Pararhinebothroides was established for a species of cestode (Parahinebothroides hobergi) found parasitizing the Tumbes round stingray, Urobatis tumbesensis (McEachran & Chirichigno), in the inshore Pacific waters in the Gulf of Guayaquil, Ecuador. Its apparent affinities with the freshwater endemic genus Rhinebothroides were considered evidence to support the long-standing, yet controversial, biogeographical hypothesis that freshwater stingrays of the family Potamotrygonidae derived from a Pacific marine ancestor during the Cretaceous Period before the uplifting of the Andes. Here, we re-evaluate the phylogenetic and taxonomic status of P. hobergi based on examination of the available type material and newly collected material from the type host near the type locality. The new material allowed the description of tegumental structures using scanning electron microscopy and the generation of a hypothesis for the phylogenetic position of the species based on molecular data for the first time. Morphological investigations revealed that P. hobergi shares all the diagnostic features of the most recent concept of Anthocephalum, including the previously overlooked presence of bothridial apical suckers. Phylogenetic analyses based on partial 28S rDNA (D1-D3) and complete 18S rDNA sequence data for 4 specimens of P. hobergi, 45 species of other rhinebothriideans, and 5 non-rhinebothriidean outgroup species provided unequivocal support for the transfer of P. hobergi to Anthocephalum. Since this is the type and only species of the genus, Pararhinebothroides is considered a junior synonym of Anthocephalum, and Anthocephalum hobergi n. comb. is redescribed. Furthermore, our results reveal Rhinebothroides and Anthocephalum to be only distantly related among the Rhinebothriidea. Not only do our results confirm reservations expressed earlier about the affinities of P. hobergi, but they also substantially challenge inferences drawn previously about the biogeographical history of potamotrygonid stingrays based on parasitological data.

A new marine leech is herein described from specimens infecting the external surfaces, including the mouth and cloaca, of the banded guitarfish, Zapteryx exasperate, captured in the Gulf of California and eastern Pacific Ocean off the coast of San Diego, California. The leech is assigned to Austrobdella by possessing continuous contractile coelomic channels that lie outside the somatic musculature along the lateral edges of the urosome (marginal lacunae), clitellar gland cells densely packed in the urosome, 5 pairs of testisacs, and 6-annulate mid-body somites. The new leech is distinguished from its 6 congeners on the basis of body size (maximum 10 mm long) and shape (sub-cylindrical trachelosome distinctly demarcated from wider urosome that is ventrally flattened, convex dorsally, and narrowing toward caudal sucker that is narrow, 20-25% of maximum body width), number of eyespots (2 pairs), shape and arrangement of the ovisacs (pyriform and limited to somites XII/XIII), and characteristics of the midgut (1 pair of mycetomes, 6 pairs of simple thin-walled crop ceca, ventral postceca wanting, and 2 pairs of dendritic diverticula emerging from anterior portion of thick-walled intestine). The new species occurs in the northeastern Pacific Ocean on a benthic elasmobranch. Examination of host specificity for each Austrobdella species using the quantitative Index of Phylogenetic Host Specificity revealed that the new species is 1 of 4 oioxenous specialists in the genus, and the remaining 3 congeners are relative generalists herein classified as euryxenous. This is the first time host specificity for members of the Piscicolidae has been quantitatively assessed. The analysis suggests that associations between marine leeches belonging in Austrobdella and their vertebrate hosts are driven by ecological influences rather than host taxonomic placement.

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.

Scanning and transmission electron microscopical observations were made of the surface topography of Dictyocotyle coeliaca (Nybelin, 1941) (Monopisthocotylea: Monocotylidae), a unique endoparasitic monogenean from the body cavity of the ray Amblyraja radiata (Elasmobranchii: Rajidae). Scanning investigation show the presence on the ventral side of the anterior body of smooth areas with pit-like depressions and shallow ridges, whereas the tegument of the middle and posterior regions of the body is extensively folded, and on the dorsal surface the tegument is smooth but interrupted by deep depressions. Transmission observation revealed the presence of invaginations of varying irregularity and depth, which form the various depressions of the tegumental surface. Non-ciliated, dome-shaped papillae occur singly or in groups and are common around the mouth and both the genital and vaginal pores, but exhibit no particular orientation. The haptor is much reduced, compared with that of ectoparasitic monocotylids, and is covered ventrally with an irregular array of 40-70 shallow loculi. Internal differences occur in the thickness of the syncytial tegumentary layer of the haptoral loculi and septa and also in the number of cytoplasmic inclusions. The locular surface has distinct ultrastructural characteristics, the most obvious of which are a honeycomb arrangement of small pockets measuring 0.6 × 0.75 to 1.0 × 1.7 μm in diameter, a terminal web beneath the surface plasma membrane and large outgrowths on the surface of the loculi filled with lysosome-like bodies. The surface specializations of the body and haptoral tegument of D. coeliaca are discussed in relation to their being adaptations to an endoparasitic environment.

Currently, the caligid genus Euryphorus Milne Edwards, 1840 contains two valid species. A new species, Euryphorus suarezi, is described based on adult females and males collected from the spotted eagle ray Aetobatus narinari (Euphrasen) (Elasmobranchii: Myliobatidae), captured off Campeche and Tabasco, Mexico (southern coast of the Gulf of Mexico). The new species is mainly distinguished from its congeners by the absence of dorsal plates, the presence of postantennal process, bifurcated maxillule, maxilliped with slender corpus, and leg 4 with 3-segmented endopod. Leg 6 is conspicuous in the male. Additional differences are described. This is the first record of a species of Euryphorus from an elasmobranch host, which may provide insight into the evolutionary relationships within the Caligidae.

The sensory organs in tegument of two trypanorhynchean species--Nybelinia surmenicola (plerocercoid) and adult Parachristianella sp. (Cestoda, Trypanorhyncha)--were studied with the aim of ultrastructural description and a comparative analysis. The Nybelinia surmenicola plerocercoid lacks papillae with sensory cilia on the bothria adhesive surface. We found an unciliated sensory organ within the median bothria fold. This unciliated free nerve ending contains the central electron-dense disc, three dense supporting rings, and broad root. The nerve ending locates in the basal matrix under the tegument. The tegument of N. surmenicola has a number of ultrastructural features which make it significantly different from other Trypanorhyncha: (i) the tegumental cytoplasm has a plicated constitution in a form of high apical and deep basal folds, (ii) numerous layers of the basal matrix are presented in the subtegument, and (iii) the squamiform and bristlelike microtriches N. surmenicola lack the base and the basal plate. In contrast, numerous ciliated and unciliated receptors were found in Parachristianella sp.: six types on the bothria and one type in the strobila tegument. Ultrastructural constitution of sensory organs in the form of ciliated free nerve endings as well as unciliated basal nerve endings of Parachristianella sp. has many common features inside Eucestoda. In comparison with other Trypanorhyncha, all Nybelinia species studied have less quantity of the bothrial sensory organs. This fact may reflect behavioral patterns of Nybelinia as well as phylogenetic position into Trypanorhyncha. Our observations of living animals conventionally demonstrate the ability of N. surmenicola plerocercoids to locomote in forward direction on the Petri dish surface. The participation of the bothrial microtriches in a parasite movement has been discussed.

A new species of the genus Dollfusiella Campbell & Beveridge, 1994 is described from Pastinachus sephen (Forsskål) in the Persian Gulf. Dollfusiella qeshmiensis n. sp. is allocated to the genus Dollfusiella based on the possession of two bothria, prebulbar organs, a heteroacanthous typical armature with tightly spaced rows of hollow hooks, a basal swelling and a characteristic basal armature without prominent macrohooks. The presence of an enlarged external seminal vesicle in Dollfusiella qeshmiensis n. sp. distinguishes this species from D. michiae (Southwell, 1929), D. bareldsi (Beveridge, 1990), D. owensi (Beveridge, 1990), D. geraschmidti (Dollfus, 1974), D. angustiformis Schaeffner & Beveridge, 2013, D. hemispinosa Schaeffner & Beveridge, 2013, D. spinosa Schaeffner & Beveridge, 2013 and D. taminii Menoret & Ivanov, 2014. The new species is distinguished from the remaining species within the genus by a combination of the following morphological features: the number of testes per segment, the number of testis columns and the number of homeomorphous hooks per half spiral row in the metabasal region. In the most recent taxonomic key to the species of Dollfusiella, the presence or absence of enlarged, microscopically visible spinitriches on the scolex was used as the first distinguishing character dividing the congeners into two groups. Since the existence of visible microtriches on the scolex peduncle of D. vooremi (São Clemente & Gomes, 1989), a species so far grouped among the species lacking visible microtriches on the scolex, has been recently demonstrated, and given the fact that the presence of microscopically visible microtriches on the scolex is variable in some eutetrarhynchid species, a new key to the species of Dollfusiella is provided in which the spinitriches have been given less priority.

A new fish leech Ceratobdella quadricornuta n. g., n. sp. (Hirudinida: Piscicolidae), a parasite of the Antarctic skate Raja georgiana Norman (Rajiformes: Rajidae) collected between the Falkland Islands and South Georgia Island in the Scotia Sea, is described and compared with related genera. Ceratobdella quadricornuta is characterised by an uncommon appearance of its anterior sucker bearing four well-developed tentacles and a unique combination of features of the reproductive and digestive systems: crop and intestine equally developed, posterior crop caeca separated; accessory glands, conductive tissue and external copulatory area lacking; common part of ejaculatory ducts (common atrium) voluminous and muscular, male copulatory bursa short, small ovisacs opening into female copulatory bursa (vagina).

Four new species are described in the lecanicephalidean genus Hornellobothrium from the ocellated eagle ray, Aetobatus ocellatus, from Australia and Indonesian Borneo. The species possess flat, laterally expanded immature proglottids and a small internal, glandular apical organ diagnostic of the genus. To date, only 2 valid species are recognized in the genus: Hornellobothrium cobraformis Shipley & Hornell, 1906 , from " Aetobatus narinari " from Sri Lanka, and Hornellobothrium extensivum Jensen, 2005 , from A. ocellatus , also from Australia. The new species differ from H. cobraformis in the shape of the apical organ and mature proglottids, and from H. extensivum in testes number and scolex dimensions. The new species can be distinguished from one another based on the following combination of features: Hornellobothrium gerdaae n. sp. possesses testes arranged in 2 layers and lacks post-ovarian vitelline follicles; Hornellobothrium iotakotta n. sp. has a single column of 4 testes and lacks spiniform microtriches on the distal bothridial surface; both Hornellobothrium kolossakotta n. sp. and Hornellobothrium najaforme n. sp. possess a single column of 6 testes, but H. najaforme n. sp. is a longer worm with a greater number of laterally expanded immature proglottids. Host associations suggest this genus is potentially limited to A. ocellatus . While reports of up to 9 lecanicephalidean congeners in a single host species exist, they are considered dubious and in need of verification, mainly because of host identification issues. This study demonstrates the presence of at least 5 species of Hornellobothrium in A. ocellatus . Insufficient sampling of this host species across the Indo-Pacific and at each locality may account for the apparent restricted distribution of species of Hornellobothrium.

Floriparicapitus n. gen. (Cestoda: Lecanicephalidea), with Floriparicapitus euzeti n. gen., n. sp. as its type, is erected to house 3 new tapeworm species and 2 known species that are transferred to the new genus, all parasitizing sawfishes and guitarfishes (order Rhinopristiformes) in Indo-Pacific waters. The new genus differs from the 21 valid lecanicephalidean genera in its possession of a large scolex bearing a laterally expanded apical organ in the form of a rugose sheet in combination with a cirrus conspicuously armed with spinitriches and 3 pairs of excretory vessels. It most closely resembles Lecanicephalum, but differs conspicuously in its possession of 3, rather than 1, pair of excretory vessels. Two new species are described from sawfishes: Floriparicapitus euzeti n. sp., from Pristis clavata and Floriparicapitus juliani n. sp. from Pristis pristis, both from Australia. Floriparicapitus plicatilis n. sp. is described from the guitarfish Glaucostegus typus in Australia and the guitarfish Glaucostegus thouin in Malaysian Borneo. Two species formerly assigned to Cephalobothrium are transferred to the new genus; Floriparicapitus variabilis ( Southwell, 1911 ) n. comb. from the sawfish Anoxypristis cuspidata in Sri Lanka and Floriparicapitus rhinobatidis ( Subhapradha, 1955 ) n. comb. from the guitarfish Glaucostegus granulatus in India. The species from guitarfish differ conspicuously from those parasitizing sawfish in their possession of only 4 ( F. plicatilis n. sp.) or 5 (F. rhinobatidis n. comb.) testes per proglottid versus 9 or more in the 3 sawfish-parasitizing species. The latter 3 species differ from one another in scolex width, acetabular size, number of proglottids, and cirrus sac size. As it stands, the new genus appears to be restricted to a subclade of the Rhinopristiformes consisting of the sawfishes and species of Glaucostegus.

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.

The genus Eutetrarhynchus Pintner, 1913 is revised. Eutetrarhynchus beveridgei n. sp. is described from the spiral intestine of the dwarf whipray, Himantura walga (Müller & Henle) (Myliobatiformes: Dasyatidae), from the South China Sea off the Malaysian part of Borneo. The new species is characterised by a slender, elongate scolex, two oval bothria, muscular bulbs, retractor muscles inserting at the base of the bulbs, and the presence of gland-cells and prebulbar organs. The tentacular armature is typical heteroacanthous with heteromorphous hooks. Eutetrarhynchus beveridgei n. sp. is allocated to the genus due to its distinct segment morphology featuring two internal seminal vesicles and scattered testes occupying the complete intervascular space. It differs from congeners in its relatively small size, much smaller scolex regions and in the presence of a basal armature with a distinct basal swelling. Eutetrarhynchus cortezensis Friggens & Duszynski, 2005 is transferred to Dollfusiella Campbell & Beveridge, 1994, as D. cortezensis n. comb., on the basis of its segment morphology, with testes in a linear arrangement and the absence of internal seminal vesicles. A new generic diagnosis and a key for the identification of species of Eutetrarhynchus is provided.

Two new species of Acanthobothrium van Beneden, 1850 from the spiral intestine of Pastinachus cf. sephen Forsskål from the Iranian coast of the Persian Gulf and the Gulf of Oman are described. To analyse the surface ultrastructure the worms were studied using light and scanning electron microscopy. Acanthobothrium jalalii sp. n. belongs to the category 1 species of the genus so far including 43 species. This tiny new species differs from the other category 1 species by its small total length (2.18 +/- 0.49 mm), number of proglottids (4.7 +/- 0.9) and testes (24 +/- 3), terminal segments in an apolytic condition and the shape of the cirrus-sac. Acanthobothrium sphaera sp. n. is a small worm that belongs to the category 2 species of the genus so far including 36 species. A. sphaera sp. n. differs from the other category 2 species by its small total length (1.6 +/- 0.2 mm), number of proglottids (9.6 +/- 1.2) and testes (12 +/- 1), the presence of a vaginal sphincter and the shape of the ovary. This is the first report of Acanthobothrium from the cowtail stingray, P cf. sephen, from the Persian Gulf and Gulf of Oman. Pastinachus sephen sensu lato has been reported as a common host of species of Acanthobothrium. Most recently, the host genus Pastinachus Rüppell has been split into five nominal species and several Acanthobothrium species infect the newly described congeners but not P. sephen. The real identity of the host studied within the present study is still in question, since sequence data of three specimens from the Gulf of Oman do not correspond to P. sephen sensu stricto.

Two new species of diphyllidean cestodes of the genus Echinobothrium, each hosted by a different skate species in the Raja miraletus complex, are described. Echinobothrium mercedesae n. sp. is described from R. cf. miraletus 2 off Senegal. Echinobothrium yiae n. sp. is described from R. cf. miraletus 1 off South Africa. Both species are small worms that differ from their 29 described congeners in the combination of number of cephalic peduncle spines per column, hook formula, number and arrangement of testes, and arrangement of vitelline follicles. They are easily distinguished from one another in that whereas the vitelline follicles of E. yiae n. sp. are circumcortical, they are lateral in E. mercedesae n. sp., and also in number of cephalic peduncle spines per column (14-17 vs. 10-12). Echinobothrium yiae n. sp. is also unusual in that the cephalic peduncle spines stop short of the anterior margin of the peduncle. In addition, although the paucity of available material precluded their formal description, evidence of 2 additional new species parasitizing R. miraletus also from Senegal is presented. In combination these worms provide support for the interpretation that what is currently recognized as Raja miraletus actually consists of a complex of geographically restricted species, rather than a polymorphic species of multiple parapatric or allopatrically distributed populations. This interpretation is not only supported by previously published molecular data, but also by newly collected morphological data involving differences in the color patterns of disc ocelli among host specimens of the 3 forms available as a result of digital efforts to ensure the accuracy of host identifications, which are also presented here.

A new species of Hexabothriidae, Mobulicola enantiomorphica n. gen., n. sp., is described on the basis of specimens collected from the gill of a lesser devil ray, Mobula hypostoma (Bancroft, 1831) (Rajiformes: Mobulidae), captured in the northern Gulf of Mexico (30°13'49.22″N, 88°20'31.69″W) off Dauphin Island, Alabama. We also herein redescribe Mobulicola dubium (Euzet and Maillard, 1967) n. comb. on the basis of the holotype (36HG-69-1) and paratypes (36HG-69-2 and 36HG-69-3) collected from the gill of a lesser Guinean devil ray, Mobula rochebrunei (Vaillant, 1879), captured in the eastern Atlantic Ocean off the island of Gorée (14°40'02.26″N, 17°23'4.96″W), Senegal. Mobulicola has the following combination of diagnostic features that differentiate it from other hexabothriid genera: haptor symmetrical; vasa efferentia narrow for entire length (not dilated distally), glandular-walled, joining medially immediately anterior to testicular field; vas deferens glandular for part or all of length and extensively convoluted; male copulatory organ massive, oblong, unarmed, dilated for entire length, lacking prostatic region; seminal receptacle present; ootype lacking longitudinal rows of large cells (ootype côtelé); vaginae parallel, with well-differentiated proximal (narrow, tube-like) and distal (laterally expanded, musculoglandular) portions; uterine eggs with 2 elongate filaments. Mobulicola is morphologically most similar to Branchotenthes Bullard and Dippenaar, 2003 but differs from it by the combination of having short, delicate vasa efferentia that are narrow for their entire length and that each extends slightly anteriad from the testicular field before uniting medially, a vas deferens that is convoluted between the common vitelline duct and male copulatory organ, an ovate, compact seminal receptacle, an ovary that ascends, descends, then ascends, and a proximal uterus that is extensively convoluted posterior to the male copulatory organ. The new species differs from M. dubium by the combination of having a proportionally shorter sclerite hook (19-29% of sclerite shaft total length), a vas deferens that is glandular-walled and laterally expanded proximally and nonglandular and narrow distally, and a common vitelline duct with dextral and sinistral loops extending anteriad. This is only the second report of a hexabothriid from a mobulid and the first report of a monogenoid from Mobula hypostoma.

Recent collections of cestode parasites from two species of the myliobatid genus Aetomylaeus Garman from several localities in the Pacific Ocean resulted in the discovery of two new species of Halysioncum Caira, Marques, Jensen, Kuchta et Ivanov, 2013. Halysioncum gibsoni sp. n. from Aetomylaeus maculatus (Gray) in the South China Sea off Borneo differs from all of its congeners in having the following combination of characters: 27 apical hooks (14 type A and 13 type B hooks), 11-12 lateral hooklets, 22-28 spines per column on the cephalic peduncle, testes distributed in a single column and an internal seminal vesicle. Halysioncum arafurense sp. n., recovered from Aetomylaeus cf. nichofii 2 (sensu Naylor et al. 2012b) in the Arafura Sea off the Wessel Islands, Northern Territory, Australia, can be distinguished from its congeners based on the following combination of characters: 23 apical hooks (12 type A and 11 type B hooks), the number of lateral hooklets (9-11), the number of spines per column on the cephalic peduncle (20-24), the number and distribution of the testes (13-15 testes in two irregular columns), and the distribution of vitelline follicles (interrupted dorsally at the level of the ovarian lobes). Both species represent the first verified records of diphyllideans from eagle rays of the genus Aetomylaeus and formally extend the host associations of diphyllideans to include a third genus of Myliobatiformes. The myliobatiforms are indeed an understudied group of available hosts for diphyllideans and represent interesting target hosts if the diversity of diphyllidean tapeworms is to be fully estimated and understood.

The caligid genus Pupulina van Beneden, 1892 currently has three accepted species. Two new species, Pupulina cliffi n. sp. and P. merira n. sp., are described from Mobula kuhlii (Müller & Henle) and M. eregoodootenkee (Bleeker) (Mobulidae) caught along the east coast of South Africa. Pupulina cliffi can be distinguished from all the other species by the absence of posterolateral processes on the genital complex, whereas P. merira has very short, rounded posterolateral processes on the genital complex compared to the three previously known species. Additionally, P. merira is the only species with the abdomen only about two-thirds the length of the genital complex and the caudal rami about the same length as the abdomen. A dichotomous key to distinguish the five species of Pupulina is provided.

Microscopic and molecular procedures are used to describe a new myxosporean species, Chloromyxum clavatum n. sp., infecting the cartilaginous fish Raja clavata Linnaeus, 1758 (Chondrichthyes: Rajidae), collected from the northwest Atlantic coast of Portugal. Young plasmodia and mature spores were found floating free in the gall bladder of R. clavata . Spores were spherical to subspherical with a pointed anterior end, measuring14.4 ± 0.5 μm (n = 25) in length, 11.9 ± 0.5 μm (n = 25) in width, and 9.4 ± 0.5 μm (n = 15) in thickness. The spore's wall was composed of 2 equally sized valves, each displaying 6-8 elevated surface ridges and a bundle of several tapering caudal filaments attached to the basal portion. Spores contained 4 pyriform equally sized polar capsules (5.5 ± 0.4 μm × 2.9 ± 0.5 μm) (n = 25), each possessing an obliquely arranged isofilar polar filament coiled in 7-8 coils. Morphological data, host specificity, tissue tropism, and molecular analysis of the SSU rDNA gene identify this parasite as a new species of Chloromyxum. Neighbor-joining and maximum likelihood further reveal the parasite clustering with other species of Chloromyxum infecting the gall bladder of marine cartilaginous fish to form a clade positioned at the base of the freshwater clade, therefore constituting an exception to the major division of the class Myxosporea into the freshwater and marine clades, while supporting the existence of a correlation between tissue tropism and myxosporean phylogeny.

Septesinus gibsoni n. g., n. sp. (Monocotylidae: Heterocotylinae) is described from the gills of the dwarf whipray Himantura walga (Müller & Henle) collected in marine waters off Sarawak (Borneo), Malaysia. Septesinus n. g. is distinguished from other genera in the Monocotylidae by a combination of characters, including a haptor with one central and seven peripheral loculi, the presence of a highly sinuous ridge surmounting all haptoral septa, four rounded accessory structures on the dorsal surface of the haptor, and the anterior region with two pairs of anteromedian and three pairs of anterolateral gland-duct openings. Septesinus n. g. is accommodated in the Heterocotylinae. Septesinus gibsoni n. sp. is described and fully illustrated, and a key to the genera of Heterocotylinae is provided. The composition of the ridges surrounding the mouth of a number of heterocotyline species and their usefulness as a taxonomic character are examined. The identity of four specimens of Monocotyle Taschenberg, 1878, also recovered from the gills of this host species, is discussed.

A wild-caught specimen of the zonetail butterfly ray, Gymnura zonura (Bleeker), harboured numerous specimens of Hexacanalis folifer Cielocha & Jensen, 2011 (Systematic Parasitology, 79, 1-16; Cestoda: Lecanicephalidea) within its spiral intestine. The cestodes were primarily attached in single rows along the base of mucosal folds, each associated with a nodular mucosal thickening. Microscopically, the scolex was embedded within the submucosa and muscularis; the attachment sites were marked by ulceration and necro-proliferative inflammation demarcating the parasite from normal host tissues. Physical attachment of the cestode was restricted to the anterior portion of its scolex where presumed tegumental secretions from the apical organ contributed to a cementing intermediate layer blending with necrotic host cells. The presence of tegumental differentiation between the apical organ and the scolex proper, associated with presumed different roles in attachment, correlated with ultrastructural observations of the surface modifications on the scolex. Despite the locally severe pathological change, insignificant morbidity owing to this particular host-parasite relationship is suggested., (© 2012 Blackwell Publishing Ltd.)

A new species of Grillotia was found from teleosts and elasmobranchs along the Patagonian shelf off Argentina. Grillotia patagonica n. sp. is described from plerocerci recovered from gadiform (Moridae) and perciform fish (Cheilodactylidae, Bovichtidae, and Nototheniidae) and adults from the smallthorn sand skate Psammobatis rudis (Rajiformes, Rajidae). Grillotia patagonica most closely resembles species in the Grillotia erinaceus species complex (viz., Grillotia borealis, Grillotia brayi, Grillotia dollfusi, G. erinaceus, and Grillotia musculara) in having 4 hooks per principal row and 2 or more intercalary rows in the metabasal region, a band of hooks on the external surface of the tentacle, numerous proglottids, a hermaphroditic sac, internal and external seminal vesicles, uterine pore, and attachment of the retractor muscle in the mid region of the tentacular bulb. Grillotia patagonica n. sp. is unique among all valid species in the genus by having the hooks on the first row reduced and of a different shape from the rest of the metabasal rows. Despite the diversity of elasmobranchs that are available as definitive hosts for species in Grillotia, most species (10/14) are oioxenous or mesostenoxenous. The specificity for the last intermediate host is variable among species of Grillotia, with most plerocerci being oioxenous (5/15) or euryxenous (8/15). Host specificity is higher for the adult stage in the definitive host (mean HS(S) = 4.07) than for the plerocerci (mean HS(S) = 7.30). All the species with oioxenous specificity (either larvae or adults) have limited geographic distributions. Some previous records of species of Grillotia from fishes caught off Argentina require reconsideration, i.e., G. erinaceus, Grillotia minuta (reported as Grillotia bothridiopunctata) and G. borealis . An updated host-parasite checklist for the valid species of Grillotia is also presented along with new host records for Grillotia carvajalregorum.

Host-parasite interactions generally involve communities of parasites. Within these communities, species will co-exist and/or interact with one another in a manner either benefiting the species involved or to the detriment of one or more of the species. At the level of helminth infracommunities, evidence for intra- and inter-specific competition includes numerical responses, i.e. those regulating helminth intensity of infection, and functional responses, i.e. where the presence of competitors modifies the realised niche of infrapopulations. The objectives of this study are to assess the numerical and functional responses of helminths in infracommunities from 3 rajid skates using general linear models. Despite a lack of numerical responses, functional responses to intra- and inter-specific interactions were observed. A positive correlation between the number of individuals in an infrapopulation and its niche breadth (functional response) was observed for the tapeworms Pseudanthobothrium spp. and Echeneibothrium spp., in all their respective hosts, and for the nematode Pseudanisakis sp. in the little skate. Evidence for inter-specific competition includes niche shifts in Pseudanthobothrium purtoni (ex little skate) and Pseudanisakis sp. (ex thorny skate) in the presence of Pseudanisakis sp. and the tapeworm Grillotia sp., respectively. These results are consistent with other studies in providing evidence for competition between helminths of skates.

The cestode fauna of the shortfin devilray, Mobula kuhlii (Müller & Henle, 1841) was examined for the first time. The work resulted in the discovery of a new genus and species of rhinebothriidean tapeworm. Crassuseptum pietrafacei, n. gen. n. sp. is erected here on the basis of its unique scolex and proglottid morphology. Histological sections and examination by light and scanning electron microscopy demonstrated that this new genus differs from all other rhinebothriidean genera in its possession of bothridia in which the proximal and distal sides are confluent, i.e., not separated by a rim of tissue, and in its possession of testes that extend to the posterior margin of the ovary. This new species is characterized in part by its possession of stalked, elongate bothridia lacking lateral constrictions, with 13-15 prominent transverse bothridial septa and 4 reduced transverse septa, craspedote proglottids, each with 2-3 layers of testes in cross section, and a vas deferens that joins the cirrus sac at its anterior margin. Histological and optical sections through bothridial septa revealed that the transverse septa are formed by septal muscles separate from bothridial radial musculature, extending from the anterior side to the posterior side of each septum. This is only the second species rhinebothriidean cestode reported from mobulids. This study adds to the number of new species and genera of elasmobranch cestodes discovered off of the island of Borneo.

Three new species of diphyllidean cestodes are described from rhinobatid elasmobranchs of the genus Glaucostegus from the Indian and Pacific Oceans. All 3 new species have 11 apical hooks (6 type-A and 5 type-B hooks) and, therefore, differ in this feature from all but 5 of the 39 valid species of Echinobothrium. In addition, Echinobothrium tetabuanense n. sp. from Glaucostegus cf. typus in the Sulu Sea, Borneo differs from all of its congeners in the number and arrangement of hooklets, number of spines on the cephalic peduncle, and the number and distribution of testes. Echinobothrium sematanense n. sp. from Glaucostegus thouin in the South China Sea, Borneo, can be distinguished from its congeners based on the following combination of characters, i.e., small size (worms less than 1 mm long), number of hooklets, spines per column on the cephalic peduncle, and number of testes. Echinobothrium weipaense n. sp. from northern Australia is unique in the position of the cirrus sac and genital pore, both structures being well posterior and not overlapping the ovary. An emended description of the microthrix pattern on the scolex of Echinobothrium chisholmae from G. typus in Australia is also presented.

A new species of Oncomegas Dollfus, 1929 is described from the cowtail stingray, Pastinachus atrus (Macleay), collected in the Makassar Strait, Indonesian Borneo. Oncomegas trimegacanthus n. sp. possesses 2 oval bothria, gland cells within the bulbs, prebulbar organs, a distinctive basal armature with a single macrohook on the bothrial surface of the asymmetrical basal swelling, and a heteroacanthous, heteromorphous metabasal armature with 10 hooks per principle row. It differs from congeners by its possession of additional enlarged hooks at the base of the tentacle. Because of apparent morphological similarities, we suppress the genus Oncomegoides Beveridge & Campbell, 2005 with Oncomegas, and place the type and only species, Oncomegoides celatus Beveridge & Campbell, 2005 , within Oncomegas as Oncomegas celatus n. comb. Three species of Oncomegas , namely, Oncomegas paulinae Toth, Campbell & Schmidt, 1992, Oncomegas australiensis Toth, Campbell & Schmidt, 1992, and Oncomegas aetobatidis Campbell & Beveridge, 2009, differ from other species, possessing testes posterior to the ovary and a metabasal armature consisting of tiny, relatively homeomorphous hooks, with more than 14 hooks per principle row. Based on these morphological differences, a new genus, Hispidorhynchus n. gen., is erected, with Hispidorhynchus australiensis n. comb. as the type species.

New lecanicephalidean cestodes inhabiting the spiral intestine were investigated in 4 of the 6 known species of eagle rays of the genus Aetomylaeus Garman. Hosts examined consisted of 5 specimens of Aetomylaeus vespertilio from northern Australia, 5 of Aetomylaeus maculatus from Borneo, 10 of Aetomylaeus nichofii sensu stricto from Borneo, and 7 of Aetomylaeus cf. nichofii 2 from northern Australia. As a result of these new collections, 3 new genera and 6 new species of lecanicephalideans are formally described. Aetomylaeus vespertilio hosted the new genera and species Collicocephalus baggioi n. gen., n. sp. and Rexapex nanus n. gen., n. sp., as well as Aberrapex weipaensis n. sp. Aetomylaeus maculatus and A. nichofii sensu stricto hosted 3 new species of the novel genus Elicilacunosus , with the former eagle ray hosting Elicilacunosus sarawakensis n. sp. and the latter hosting both Elicilacunosus dharmadii n. sp. and Elicilacunosus fahmii n. sp. No new lecanicephalideans were described from A. cf. nichofii 2. Collicocephalus n. gen. is conspicuously unique among the genera of its order in possessing a large, retractable apical organ that, in cross-section, is transversely oblong, rather than round. Rexapex n. gen. is distinctive in its possession of an apical organ that bears 18 papilliform projections around its perimeter, and Elicilacunosus n. gen. is unlike any other known lecanicephalidean, or eucestode, in its possession of a region of musculo-glandular tissue along the midline of the dorsal and ventral surfaces of its proglottids, manifested externally as a tandem series of depressions. Among other features, A. weipaensis n. sp. differs from its congeners in its lack of post-ovarian vitelline follicles. All 6 new species were each restricted to a single species of Aetomylaeus . These records formally establish species of Aetomylaeus as hosts of lecanicephalideans. A summary of cestodes of myliobatid rays is presented.

The marine-derived stingrays of Potamotrygonidae, endemic to South American river systems, host an interesting parasite fauna equally related to marine lineages. Among those lineages, the diversity and phylogenetic relationships within Potamotrygonocotyle - a monocotylid monogenoidean specific to potamotrygonids - are poorly known, since 9 of 10 species attributed to this genus have been described in the past 3 years. Here, we readdress the diversity of Potamotrygonocotyle after examining the gills of 436 potamotrygonid individuals representing 12 described and 14 potentially undescribed species of freshwater stingrays from 19 major river systems of South America (i.e. sub-basins). We recognized 12 valid species within the parasite genus, of which four are described in this study. Our taxonomic decisions were based on the phylogenetic analysis of 14 ingroup terminal taxa and 12 morphological characters, which resulted in the following hypothesis of sister-group relationships: ((P. dromedarius, P. tatianae sp. nov.), (P. rionegrense, P. auriculocotyle sp. nov., ((P. quadracotyle, P. umbella), (P. septemcotyle sp. nov., (P. chisholmae, P. uruguayense)), (P. tsalickisi, P. eurypotamoxenus, P. rarum, (P. tocantinsense sp. nov., P. aramasae))))). According to our hypothesis, the absence of autapomorphic features for some nominal species, and the re-evaluation of morphological variation among populations, led us to consider P. eurypotamoxenus and P. uruguayense as junior synonymys of P. tsalicksi and P. chisholmae, respectively. Finally, we address the importance of biogeographic and host representation, in order to fully understand the patterns of morphological variation and host specificity within this group. We found that hypotheses of species delimitation depend greatly on efforts to sample specimens throughout its distributional range and that host specificity within this genus varies dramatically among lineages.

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.

The cestode fauna of the darkspotted numbfish, Narcine maculata (Shaw) (Torpediniformes: Narcinidae), from Malaysian Bomrneo was examined for the first time. This work resulted in the discovery of a new genus and two new species of Anteroporidae (Lecanicephalidea). Sesquipedalapex comicus gen. n., sp. n. was erected on the basis of the peculiarities of its scolex, in particular its possession of an extremely long apical modification of the scolex proper, which readily distinguishes it from the other genus in the family. The genus is also distinct in its possession of acetabula that are in the form of suckers, rather than bothridiate in form. This species was found to deeply embed its elongate apical structure for much of its length within the intestinal mucosa, provoking a papilliform expansion of the outer wall of the spiral intestine at the site of attachment. The second new species, Anteropora klosmamorphis sp. n., is readily distinguished from its congeners on the basis of testis number and bothridial shape. Both new species are hyperapolytic. The diagnosis of Anteroporidae is amended to accommodate both new taxa. This increases the total number of genera in the family to two, and the total number of species to five.

Hexacanalis Perrenoud, 1931 was erected for H. abruptus (Southwell, 1911) Perrenoud, 1931 based on the presence of six excretory vessels, a unique feature among the Lecanicephalidea. The genus has since been considered a junior synonym of Cephalobothrium Shipley & Hornell, 1906 or Lecanicephalum Linton, 1890, or as a genus inquirendum. Based on examination of the syntype series of H. abruptus, this species is redescribed and a lectotype designated. Examination of cestodes from the zonetail butterfly ray Gymnura zonura (Bleeker) from off Indonesian Borneo resulted in the discovery of a second species. Hexacanalis folifer n. sp. is unique among lecanicephalideans in its possession of an ovary that is U-shaped in cross-section and craspedote proglottids with prominent posterior dorso-ventral processes in the form of large lappets. The presence of six excretory vessels, confirmed in both species, supports the validity of Hexacanalis. An additional species, H. pteroplateae (Zaidi & Khan, 1976) n. comb., also from a butterfly ray, G. micrura (Bloch & Schneider) [as Pteroplatea micrura (Bloch & Schneider)], is transferred to this genus from Cephalobothrium Shipley & Hornell, 1906. A revised diagnosis of Hexacanalis is presented. Seven species of this genus remain species inquirendae. Hexacanalis appears to parasitise species of the Gymnuridae van Hasselt; however, specific identifications of the hosts are in need of re-evaluation. A summary of the cestode parasites of the Gymnuridae is presented.

We describe lesions associated with a seemingly intense infection of trypanorhynch plerocerci (Platyhelminthes: Cestoda: Trypanorhyncha) in the gastric wall of a female cownose ray, Rhinoptera bonasus (Myliobatiformes: Rhinopteridae) captured in the northern Gulf of Mexico. Grossly, the multitude of encapsulated, encysted plerocerci imparted a bumpy and cobbled appearance to the serosa of the stomach, and none was observed in any other tissue during routine parasitological necropsy. Histologically, the plerocerci were associated with severe intramural granulomatous gastritis, vascular ectasia and mesothelial polyposis with the exclusion of the mucosa. To our knowledge, this is the first published case study documenting platyhelminth-associated histopathological changes in the gastrointestinal tract of R. bonasus as well as that of the efficacy of immunocytochemical markers for smooth muscle actin, Factor VIII, S-100, and proliferating cell nuclear antigen in Myliobatiformes. It also may serve as a potential primer for much needed ecological investigations regarding the potential role of elasmobranchs as intermediate or 'paratenic' hosts in the life cycles of trypanorhynch cestodes., (© 2011 Blackwell Publishing Ltd.)

Background: Neotropical freshwater stingrays (Batoidea: Potamotrygonidae) host a diverse parasite fauna, including cestodes. Both cestodes and their stingray hosts are marine-derived, but the taxonomy of this host/parasite system is poorly understood., Methodology: Morphological and molecular (Cytochrome oxidase I) data were used to investigate diversity in freshwater lineages of the cestode genus Rhinebothrium Linton, 1890. Results were based on a phylogenetic hypothesis for 74 COI sequences and morphological analysis of over 400 specimens. Cestodes studied were obtained from 888 individual potamotrygonids, representing 14 recognized and 18 potentially undescribed species from most river systems of South America., Results: Morphological species boundaries were based mainly on microthrix characters observed with scanning electron microscopy, and were supported by COI data. Four species were recognized, including two redescribed (Rhinebothrium copianullum and R. paratrygoni), and two newly described (R. brooksi n. sp. and R. fulbrighti n. sp.). Rhinebothrium paranaensis Menoret & Ivanov, 2009 is considered a junior synonym of R. paratrygoni because the morphological features of the two species overlap substantially. The diagnosis of Rhinebothrium Linton, 1890 is emended to accommodate the presence of marginal longitudinal septa observed in R. copianullum and R. brooksi n. sp. Patterns of host specificity and distribution ranged from use of few host species in few river basins, to use of as many as eight host species in multiple river basins., Significance: The level of intra-specific morphological variation observed in features such as total length and number of proglottids is unparalleled among other elasmobranch cestodes. This is attributed to the large representation of host and biogeographical samples. It is unclear whether the intra-specific morphological variation observed is unique to this freshwater system. Nonetheless, caution is urged when using morphological discontinuities to delimit elasmobranch cestode species because the amount of variation encountered is highly dependent on sample size and/or biogeographical representation.

Empruthotrema chisholmae n. sp. is described from specimens recovered from a bull ray Pteromylaeus bovinus (Geoffroy Saint-Hilaire, 1817) at the Oceanogràfic Aquarium in Valencia, Spain. The bull ray was caught in the Spanish Mediterranean (Puerto de Mazarrón, Murcia). The new species resembles 4 others of the same genus ( Empruthotrema dasyatidis Whittington and Kearn, 1992, Empruthotrema kearni Whittington, 1990, Empruthotrema stenophallus Chisholm and Whittington, 2005, and Empruthotrema tasmaniensis Chisholm and Whittington, 1999) in having a haptor with 13 marginal loculi, the posteriormost loculus single and medial. The new species can be distinguished from these other species of the genus by the morphology of the sclerotized male copulatory organ, which is the shortest described. The new species also differs from the other species by the following combination of features: haptor with 13 marginal loculi, the presence of eyespots, the absence of an accessory piece associated with the male copulatory organ, and a long egg appendage (more than 150 µm). Empruthotrema chisholmae is the first species of the genus reported from the Mediterranean.

Neoheterocotyle robii n. sp. is described from the gills of four female Rhinobatos annulatus Müller & Henle caught as bycatch during routine demersal research trawls off the Southern Cape coast of South Africa. The new species can be distinguished from all other members of Neoheterocotyle Hargis, 1955 by the morphology of the accessory piece associated with the male copulatory organ, the presence of a distinct horseshoe-shaped muscle associated with the male copulatory organ and the presence of a sclerotised structure in the proximal portion of the vagina. This is the first Neoheterocotyle species described from South African waters.

The study of 4 dasyatid stingrays- Dasyatis centroura (Mitchill, 1815), D. americana Hildebrand and Schroeder, 1928, D. say (Lesueur, 1817), and D. sabina (Lesueur, 1824)-from the northwestern Atlantic and the Gulf of Mexico showed the presence of monocotylid monogeneans Thaumatocotyle Scott, 1904 in their nasal fossae. Specimens collected from D. centroura from the northern Atlantic were identified as T. dasybatis (MacCallum, 1916). This confirmed the incorrect type host attribution of D. pastinaca (Linnaeus, 1758), which does not occur in the geographic area where T. dasybatis was described. Monogeneans collected from D. americana and D. say in the western Atlantic and the Gulf of Mexico were identified as T. longicirrus Hargis, 1955 and T. retorta Hargis, 1955, respectively, which corresponds to the opposite hosts attributed for each parasite species compared with their original description in the Gulf of Mexico. The species T. roumillati de Buron and Euzet, 2005 described from D. sabina in the northwestern Atlantic is reported for the first time in D. sabina from the Gulf of Mexico. Results clarify confusion in the literature regarding the hosts and habitats of Thaumatocotyle from dasyatids of the western Atlantic and Gulf of Mexico and support the oioxenous specificity of these monogeneans as well as their specificity for the nasal fossae of their hosts.

Trypanorhynch tapeworms (Platyhelminthes: Cestoda) are among the most diverse and abundant groups of metazoan parasites of elasmobranchs and are a ubiquitous part of the marine food webs that include these apex predators. Here we present a comprehensive analysis of their phylogeny, character evolution and host associations based on 10years of sampling effort, including representatives of 12 of 15 and 44 of 66 currently recognized trypanorhynch families and genera, respectively. Using a combination of ssrDNA and lsrDNA (Domains 1-3) for 79 and 80 taxa, respectively, we maintain one-to-one correspondence between molecules and morphology by scoring 45 characters from the same specimens used for sequencing, and provide museum vouchers for this material. Host associations are examined through likelihood-based ancestral character state reconstructions (ACSRs) and by estimating dates of divergence using strict and relaxed molecular clock models in a Bayesian context. Maximum parsimony and Bayesian inference analyses of rDNA produced well-resolved and strongly supported trees in which the trypanorhynchs formed two primary lineages and were monophyletic with respect to the diphyllidean outgroup taxa. These lineages showed marked differences in their rates of divergence which in turn resulted in differing support and stability characteristics within the lineages. Mapping of morphological characters onto the tree resulting from combined analysis of rDNA showed most traits to be highly plastic, including some previously considered of key taxonomic importance such as underlying symmetries in tentacular armature. The resulting tree was found to be congruent with the most recent morphologically based superfamily designations in the order, providing support for four proposed superfamilies, but not for the Tentacularioidea and Eutetrarhynchoidea. ACSRs based on the combined analysis of rDNA estimated the original hosts of the two primary parasite lineages to be alternatively rajiform batoids and carcharhiniform sharks. This fundamental split provides independent support for rejecting the notion that rays are derived sharks, and thus supports the most recent molecular phylogenies of the Neoselachii. Beyond the basal split between shark- and ray-inhabiting lineages, no pattern was found to suggest that the trypanorhynchs have closely tracked the evolutionary histories of these host lineages, but instead, it appears that host-switching has been common and that the subsequent evolution of the parasites has been ecologically driven primarily through overlap in the niches of their shark and ray hosts. Using a relaxed molecular clock model calibrated by means of host fossil data, the ray-inhabiting lineage is estimated to have diversified around the Jurassic-Cretaceous boundary, whereas the shark-inhabiting lineage is estimated to have diversified later, in the Middle Cretaceous. Although the large error associated with the estimated divergence dates prevents robust conclusions from being drawn, the dates are nevertheless found to be consistent in a relative sense with the origins of their major hosts groups. The erection and definition of the suborders Trypanobatoida and Trypanoselachoida, for the major clades of trypanorhynchs parasitizing primarily rays and sharks, respectively, is proposed for the two primary lineages recovered here., (2009. Published by Elsevier Ltd. All rights reserved.)

Dwarf razor clams (Ensis minor) in the Gulf of Mexico are known to be infected with plerocercoid larvae of a tetraphyllidean tapeworm. Here, we show that these larvae live unencysted in the intestinal lumen of the clam. Morphologically, the larvae are similar to (although significantly larger than) tapeworm larvae previously described living in the gut of amphioxus (Branchiostoma floridae) from the same habitat. Sequence data from the D2 region of the 28S rDNA from clam-infecting larvae were identical to the sequence of Acanthobothrium brevissime isolated as larvae from amphioxus and as adults from a stingray (Dasyatis say). The sequence data leave little doubt that the dwarf razor clam and the amphioxus are alternative intermediate hosts in the life cycle of A. brevissime.

Among tetraphyllidean cestodes, parasitic in the spiral valve of Raja asterias Delaroche, colected from Algerian coasts, we obtained an onchobothriid of the genus Acanthobothrium, differing from all species of Acanthobothrium previously reported from Rajidae from Mediterranea and european Atlantic coast. This Cestode is characterized by its very small size (1-2 mm), its number of segments of the strobila (4-8), the morphology and size of hooks, the limited number (17-25) of testes and ovarian morphology. Together, these features places this Acanthobothrium in group "2" as defined by Ghoshroy & Caira (2001). We describe this onchobothriid as Acanthobothrium minus n. sp.

Complete ssrDNA and partial lsrDNA (D1-D3) of 31 species, mainly from the Indo-Pacific region, were sequenced and added to 66 species of the marine cestode order Trypanorhyncha; thus 35% of the 277 known species were sampled. The resulting phylogenetic tree resolved two major clades that represent trypanorhynchs originally parasitizing rajiform (skate and ray) or galeoform hosts. The tree topology supports an earlier classification based on morphology that splits the order into the superfamily Eutetrarhynchoidea together with the Tentacularioidea, and the Gymnorhynchoidea together with the Lacistorhynchoidea and Otobothrioidea. Three of the five recognized superfamilies are monophyletic (Tentacularioidea, Gymnorhynchoidea, Otobothrioidea). Nodal support for the Eutetrarhynchidae and Lacistorhynchidae was poor and resulted in paraphyletic clades. Mapping of morphological characters showed the tentacular armature of the scolex to be highly variable within clades, demonstrating that armature patterns used traditionally in classification, are homoplasious. Similarly, the tetrabothriate scolex, currently utilized as a family-distinguishing character in traditional classifications, has developed independently in multiple groups. Synapomorphies for the higher taxa are detailed. Sequence data from duplicate taxa confirmed interoceanic distribution patterns and low intraspecific genetic divergence and host specificity for nine trypanorhynch species belonging to five families and four superfamilies. Four distinct lineages of trypanorhynchs can be recognized with one mainly infecting rajiform hosts whereas the others infecting both, sharks and rays. Eutetrarhynchoids and tentacularioids have secondarily invaded shark hosts whilst utilising the marine food web involving teleost fishes as intermediate hosts. Three cases of host switching from sharks to rays can be inferred within the lacistorhynchoids, in one case caused by a switch from perciform to gadiform intermediate hosts. This likely enabled a radiation into the deep sea environment. Implications of the molecular phylogeny for the classification and evolutionary developments within the order are discussed.

Rhinebothrium paranaensis n. sp. (Tetraphyllidea: Cestoda) is described from the freshwater stingray Potamotrygon falkneri collected in the Colastiné River, a tributary to the Lower Parana River in Argentina. The specimens were studied in detail using light and scanning electron microscopy and histology. Rhinebothrium paranaensis can be distinguished from all valid species in the genus using the following combination of characters: worm length, number of proglottids, diamond-shaped bothridia lacking constriction, number of loculi on the distal surface of bothridium, and the lack of vaginal sphincter and external seminal vesicle.

In total, 20 fanrays, Platyrhina sinensis (Rajiformes: Rhinobatidae), collected from the Taiwan Strait, were examined. A new phyllobothriid genus and species (Tetraphyllidea: Phyllobothriidae) was found and described. Biotobothrium platyrhina n. gen., n. sp. is assigned to the Rhinebothriinae Euzet, 1953, because it possesses 4 stalked bothridia that are each divided by septa into numerous small facial loculi but that lack apical suckers. The new genus and species is clearly different from any other in Rhinebothriinae in that each bothridium bears 2 sets of 5 small facial loculi, with 1 set located at each of the distal ends of the bothridium, rather than facial loculi throughout the entire distal surface of the bothridium, as is seen in all other genera in the subfamily. This character has not been previously reported for members of Rhinebothriinae. In addition, the testicular arrangement in the anterior quarter of the proglottid is unique. The posterior range of the vas deferens almost reaches the ovarian bridge, and the morphology of the cirrus sac and several other morphological characters are at variance with presently described species in the subfamily.

Five new species of Acanthobothrium van Beneden, 1850 from the spiral intestine of a specimen of an unusual species of Himantura from the Arafura Sea off northern Australia are described. Acanthobothrium oceanharvestae sp. n. is one of 26 category 1 species (sensu Ghoshroy and Caira 2001) lacking post-ovarian testes; it differs from these in total length, number of proglottids, number of testes, cirrus sac size and details of the terminal genitalia. Acanthobothrium popi sp. n. is unique among category 2 species in its possession of post-ovarian testes. Acanthobothrium rodmani sp. n. is a category 6 species distinct from all congeners in the dense blade-like spinitriches on the distal surfaces of its anterior-most bothridial loculi and conspicuously tapered posterior bothridial margins, which are reflexed anteriorly. Acanthobothrium romanowi sp. n. differs from most other category 1 species in that its genital pore is distinctly posterior. It differs from the remaining category 1 species in size, testis number, cephalic peduncle microthrix form, proglottid shape, and bothridial loculus dimensions. Acanthobothrium zimmeri sp. n. is among the six category 1 species with post-ovarian testes. It differs from these species in total length, ovary shape, number of proglottids and testes and vas deferens extent. This brings the number of Acanthobothrium species with post-ovarian testes to 10, all of which are Indo-Pacific in distribution, and 7 of which parasitize Himantura species. A key to the five new species parasitizing Himantura sp. is provided. Sequence data for the D1-D3 region of 28S rDNA for the five new species and two congeners parasitizing other Himantura species shows no intraspecific variation. Analysis of these and comparable data for two species available in GenBank (Acanthobothrium parviuncinatum and Acanthobothrium sp. 1) showed an interspecific variation of 0.7-11.3% among species pairs. Bayesian, Likelihood and Parsimony phylogenetic analyses of these data for these nine species indicate that the five new species parasitizing Himantura sp. are generally not each others' closest relatives.

Dendromonocotyle lotteri sp. n. is described from the dorsal skin surface of the stingray Himantura gerrardi (Gray) on exhibit in the public aquarium at the Atlantis resort in Dubai. It is differentiated from all other Dendromonocotyle species by the unique morphology of the distal portion of the sclerotised male copulatory organ. Dendromonocotyle lotteri is the second representative in the genus with 56 marginal haptoral papillae having a papillae to loculus association represented numerically as 6-6-8-8. We found Dendromonocotyle colorni Chisholm, Whittington et Kearn, 2001 on the same host specimens at the Atlantis resort public aquarium and Dendromonocotyle kuhlii Young, 1967 on Neotrygon kuhlii (Müller et Henle) kept at Burgers' Zoo Aquarium in Arnhem, The Netherlands. Supplemental information is provided for both D. colorni and D. kuhlii. The presence of Dendromonocotyle infections in public aquaria and host specificity are discussed. A key to the 17 species of Dendromonocotyle is also provided.

We describe a new myxozoan parasite found infecting the gall bladder of the cartilaginous fish Rioraja agassizii (Rajidae) from the South Atlantic coast of Brazil. Light microscopy, scanning and transmission electron microscopy and phylogenetic data were used. Numerous irregular polyspqric plasmodia externally covered by numerous microvilli containing different stages of sporogony, including free spores, were observed in bile. Ellipsoidal spores, on average 11.41 microm long, 8.48 microm wide and 7.32 microm thick, were formed by 2 equal-sized valves, each possessing 3 to 4 (rarely 5) elevated ridges which projected from the basal portion of the spore, and joined along a sinuous S-shaped sutural line. The basal portion of the valves bore a bundle of 33 to 37 extended tapering caudal filaments attached to the basal portion of the last ridge and basal portion of the sutural edge of the 2 valves. The caudal filaments, formed of material similar to the valves, were attached to the shell wall by a conical basis. The spores contained 4 equal-sized pyriform polar capsules (4.5 x 2.4 microm), located at the same level, each with a polar filament with 6 (rarely 7) coils. Binucleate sporoplasm was irregular in shape, with a granular matrix and dense bodies randomly distributed in a light area. Based on the shape and dimensions of the spore, on the number, position and arrangements of the surface ridges, caudal bundle of filaments, polar capsules and polar filament arrangements, as well as phylogenetic analyses using the small subunit ribosomal DNA (SSU rDNA) sequences, we propose the name Chloromyxum riorajum for this new myxozoan.