Cestode parasites in Potamotrygon motoro (Natterer) (Chondrichthyes: Potamotrygonidae) from southwestern Brazil, including Rhinebothroides mclennanae n. sp. (Tetraphyllidea: Phyllobothriidae), and a revised host-parasite checklist for helminths inhabiting neotropical freshwater stingrays.

Specimens of 5 species of cestodes were collected in 6 specimens of the freshwater stingray species Potamotrygon motoro (Natterer), collected in the vicinity of Corumba, Mato Grosso do Sul, Brazil. Acanthobothrium regoi, Potamotrygonocestus orinocoensis, Rhinebothroides venezuelensis, and Rhinebothrium paratrygoni are reported from P. motoro and from southwestern Brazil for the first time. Rhinebothroides mclennanae n. sp. appears to be the sister species of Rhinebothroides glandularis, the only other member of the genus exhibiting darkly staining glandular cells lying free in the parenchyma surrounding the terminal genitalia. The new species resembles Rhinebothroides glandularis, Rhinebothroides freitasi, and Rhinebothroides scorzai by having poral ovarian arms that extend anteriorly beyond the posterior margin of the cirrus sac, coiled vaginae, and vitelline follicles not interrupted on the poral side in the vicinity of the genital pore. It differs from all 6 previously described members of the genus by possessing an average of 31 testes per proglottid, compared with an average of 45 for R. glandularis, 55 for R. freitasi and R. venezuelensis, 77 for Rhinebothroides circularisi and Rhinebothroides moralarai, and 80 for R. scorzai. An updated phylogenetic tree for Rhinebothroides is presented.     

Cestodes of cestodes of Peruvian freshwater stingrays

Adult tetraphyllidean tapeworms (Platyhelminthes: Eucestoda) from the spiral intestines of 3 species of potamotrygonid stingrays (Paratrygon aiereba, Potamotrygon castexi, and Portamotrygon motoro) in the Madre de Dios river in Peru were found to host numerous cysts embedded in their parenchymal tissues. Histological sections of the cysts revealed the presence of a scolex bearing 4 suckers and an unarmed apical organ consistent with larval stages of both Cyclophyllidea and Proteocephalidea. To further elucidate their identities, partial 28S ribosomal DNA (rDNA) sequences were characterized from 3 cysts and 4 adult Rhinebothrium spp. 'host' worms and screened against all available cestode 28S rDNA data. Initial BLAST screening and subsequent alignment ruled out the possibility that the cysts were cyclophyllidean, and the cyst and adult sequences were thus aligned together with all available lecanicephalidean, litobothriidean, proteocephalidean, and tetraphyllidean sequences. Sequences from all 3 cysts were identical, and phylogenetic analysis clearly placed them among derived members of the Proteocephalidea, although no exact match was found. Sequences from the adult host worms formed 2 identical pairs and grouped together with other tetraphyllidean species from rays. These results are compared with records of hyperparasites of South American catfish cestodes. This is the first confirmed record of a proteocephalidean cestode parasitizing a tetraphyllidean cestode.     

Revision of Potamotrygonocotyle Mayes, Brooks & Thorson, 1981 (Platyhelminthes: Monogenoidea: Monocotylidae), with descriptions of four new species from the gills of the freshwater stingrays Potamotrygon spp. (Rajiformes: Potamotrygonidae) from the La Plata river basin

The only known monocotylid genus to parasitise Neotropical freshwater stingrays (Potamotrygonidae) is Potamotrygonocotyle Mayes, Brooks & Thorson, 1981, a monotypic genus erected to accommodate P. tsalickisi Mayes, Brooks & Thorson, 1981. For more than 20 years, no other species has been recognised in this genus, but new efforts to survey the diversity of parasites inhabiting potamotrygonids have revealed the existence of new species and the need to redefine the genus. Here, the generic diagnosis of Potamotrygonocotyle is amended, P. tsalickisi is redescribed and four new species are recognised and described based on samples collected from the gills of freshwater potamotrygonids from the La Plata river basin: Potamotrygonocotyle chisholmae n. sp. and P. dromedarius n. sp. from Potamotrygon motoro; Potamotrygonocotyle eurypotamoxenus n. sp. from Potamotrygon cf. motoro (type-host), P. castexi, P. falkneri and P. histrix; and Potamotrygonocotyle uruguayensis n. sp. from Potamotrygon brachyura. Potamotrygonocotyle is characterised by species possessing: (1) slightly sinuous sclerotised ridges on all septa; (2) two pairs of the dorsal haptoral accessory structures associated with the four posterior peripheral loculi and with anterior dorsal haptoral accessory structure bilobate or semicircular; and (3) male copulatory organ without an accessory piece.     

A new species of Acanthobothrium (Cestoda: Tetraphyllidea: Onchobothriidae) from the ocellate river stingray, Potamotrygon motoro (Chondrichthyes: Potamotrygonidae), in Argentina

Examination of the spiral intestines of 44 freshwater stingrays, Potamotrygon motoro, from tributary rivers of the Parana River in Argentina, allowed for the collection of specimens of an undescribed species of Acanthobothrium. Acanthobothrium ramiroi n. sp. can be distinguished from all other congeners by the combination of the following characters: asymmetrical hooks (medial and lateral hooks conspicuously different in size and form, with axial prong of medial hooks stouter than abaxial prong), hook size (total length of medial hooks up to 242 microm, total length of lateral hooks up to 239 microm), bothridia not fused to the scolex proper at posterior ends, worm size (51-84 mm long), and the presence of a conspicuous vaginal sphincter. The new species is different from all other species of Acanthobothrium in freshwater potamotrygonids, except Acanthobothrium terezae, in having conspicuous asymmetrical hooks. The main differences that allow for the distinction between A. ramiroi and A. terezae include hook size, the way the bothridia are attached to the scolex proper, and the shape of the older gravid segments. The discovery of a new species of Acanthobothrium from a potamotrygonid extends our understanding of the diversity of the genus in freshwater stingrays in South America.     

New genus, new species of Cestoda (Anoplocephalidae), new species of Nematoda (Cosmocercidae) and other helminths in Cyrtodactylus louisiadensis (Sauria: Gekkonidae) from Papua New Guinea

Gekkotaenia novaeguineaensis n. gen., n. sp. (Cestoda: Anoplocephalidae) from the small intestine and Cosmocerca zugi n. sp. (Nematoda: Cosmocercidae) from the large intestine of the ring-tailed gecko, Cyrtodactylus louisiadensis (Sauria: Gekkonidae) are described and illustrated. Gekkotaenia novaeguineaensis n. gen., n. sp. is unique among the acraspedote Linstowiinae in possessing a poral female reproductory system. Cosmocerca zugi n. sp. is the 22nd species to be assigned to the genus and differs from other species in the genus by possessing 4 pairs of rosette papillae on plectanes and having a gubernaculum longer than the spicules. It is the fifth species to be described from the Australian biogeographical region. Eight additional helminth species were found: the digenean, Allopharynx macallisteri; 2 cestodes, cysticercoids of Cyclophyllidea gen. sp. and tetrathyridia of Mesocestoides sp.; 5 nematodes, larvae in cysts of Abbreviata sp., Aplectana macintoshii, Oswaldocruzia bakeri, Parapharyngodon maplestonei, and an undescribed species of Physalopteroides. Cyrtodactylus louisiadensis represents a new host record for each of these helminths.     

Three new species of Rhinebothrium (Cestoda: Tetraphyllidea) from the freshwater whipray, Himantura chaophraya, in Malaysian Borneo

Three new Rhinebothrium Linton, 1890 species, R. kinabatanganensis n. sp., R. megacanthophallus n. sp., and R. abaiensis n. sp., collected from the spiral intestines of 6 freshwater whiprays (Himantura chaophraya, Dasyatidae) in the Kinabatangan River, Malaysian Borneo, are described. This is the first record of cestodes from the Kinabatangan River and from H. chaophraya. The new Rhinebothrium species are differentiated from the 34 valid Rhinebothrium species in addition to 2 species, Echeneibothrium hui Tseng, 1933 and E. oligotesticularis Subramaniam, 1940 that are herein transferred to Rhinebothrium. Each of the new species was examined with light and scanning electron microscopy. Two of the new species possess cilia on their bothridia, which have not previously been reported for members of this genus.     

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) from the freshwater stingray Himantura chaophraya (Batoidea: Dasyatidae) in Malaysian Borneo

Five new species of Acanthobothrium (Tetraphyllidea: Onchobothriidae) are described from the spiral intestine of the Freshwater whipray, Himantura chaophraya, in the Kinabatangan River in Malaysian Borneo. Based on criteria set forth in a previous categorization scheme for species of Acanthobothrium, these consist of 3 Category 1 species, Acanthobothrium asnihae n. sp., Acanthobothrium saliki n. sp., and Acanthobothrium zainali n. sp.; a Category 8 species, Acanthobothrium etini n. sp.; and a Category 2 species, Acanthobothrium masnihae n. sp.. Acanthobothrium asnihae n. sp. differs from all Category 1 species in its possession of a horizontal band of weak musculature that divides the posterior loculus in half. Among Category 1 species, A. saliki n. sp. differs from all but Acanthobothrium southwelli in its possession of postovarian testes. It differs from A. southwelli in its possession of fewer testes and a greater number of proglottids. Acanthobothrium zainali n. sp. differs from the 25 other Category 1 species in a combination of overall size, muscular pad and hook shape, arrangement and number of testes, ovary configuration in cross section, position of ovarian isthmus, and genital pore position. Acanthobothrium etini n. sp. is distinguished from all 5 other Category 8 species in its lack of testes from the proglottid antiporal and postporal regions and in testis number. Acanthobothrium masnihae n. sp. differs from the 35 other Category 2 species in its possession of fewer testes, postporal testes, or a greater number of proglottids. A key to Acanthobothrium species parasitizing H. chayophraya is presented. This represents the first report of Acanthobothrium from freshwater stingrays belonging to a family other than the Potamotrygonidae.     

Three new genera and six new species of lecanicephalideans (Cestoda) from eagle rays of the genus Aetomylaeus (Myliobatiformes: Myliobatidae) from northern Australia and Borneo

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.     

Two new species of rhabdochonids (Nematoda: Rhabdochonidae) from freshwater fishes in Mexico, with a description of a new genus

Two new nematode species, Beaninema nayaritense n. gen., n. sp. and Rhabdochona xiphophori n. sp., are described on the basis of the specimens recovered from the gall bladder and intestine of 2 fishes, Cichlasoma beani (Jordan) (Cichlidae, Perciformes) and Xiphophorus sp. (Poeciliidae, Cyprinodontiformes), respectively, from Mexico. The monotypic genus Beaninema differs from other rhabdochonid genera mainly in the presence of large conical teeth in the middle of the prostom. Rhabdochona xiphophori is characterized mainly by a unique structure of the prostom (presence of 6 anterior teeth; dorsal and ventral teeth unusually broad, with 2 lateral horns) and the shape of the deirids (bifurcated, with markedly long base).     

Intestinal helminths of some Nile fishes near Cairo, Egypt with redescriptions of Camallanus kirandensis Baylis 1928 (Nematoda) and Bothriocephalus aegyptiacus Rysavy and Moravec 1975 (Cestoda)

Of 10 species of Nile fishes collected during the summer of 1975 at Giza near Cairo, Egypt, 7 harbored 7 helminth species. Recovered material includes 3 species of nematodes: Camallanus kirandensis Baylis 1928 (new host and geographical record), Cucullanus barbi Baylis 1923, and Rhabdochona congolensis Campana-Rouget 1961 (new host record); three species of cestodes: Khawia sp. (new in Africa), Polyonchobothrium clarias (Woodland 1925) Meggitt 1930, and Bothriocephalus aegyptiacus Rysavy and Moravec 1975; and one acanthocephalan species, Acanthosentis tilapiae Baylis 1947 (new geographical record). Morphologic observations of each species are reported. C. kirandensis and B. aegyptiacus are redescribed.     

Systematics and phylogeny of Potamotrygonocestus (Platyhelminthes, Tetraphyllidea, Onchobothriidae) with descriptions of three new species from freshwater potamotrygonids (Myliobatoidei, Potamotrygonidae)

Specimens of Potamotrygonocestus used in the present taxonomic and phylogenetic study were collected in freshwater potamotrygonids from the Rio Paraná (Puerto Reconquista, Santa Fé, Argentina; 59°42'W, 29°29'S) during February 1995, and from the Amazon region of Brazil during September to December 1996, supplemented by specimens previously deposited in museum collections. Six species of Potamotrygonocestus were recognized ( P . amazonensis , P . chaoi sp. n., P . fitzgeraldae sp. n., P . magdalenensis , P . maurae sp. n., P . travassosi ), for which an identification key is provided. Potamotrygonocestus orinocoensis is considered a junior synonym of P . travassosi . Additional specimens of Potamotrygonocestus may represent two undescribed species. A phylogenetic analysis of six morphological characters for the six named species of Potamotrygonocestus generated a single tree eight steps long, with a consistency index of 0.87, a retention index of 0.90, and a rescaled consistency index of 0.79 with the following topology: ( P . maurae sp. n. (( P . amazonensis  +  P . magdalenensis ) ( P . chaoi sp. n. ( P . fitzgeraldae sp. n. +  P . travassosi )))).     

Parasites of native and nonnative fishes of the Little Colorado River, Grand Canyon, Arizona

A 2-yr, seasonal, parasitological study of 1,435 fish, belonging to 4 species of native fishes and 7 species of nonnative fishes from the lower Little Colorado River (LCR) and tributary creeks, Grand Canyon, Arizona, yielded 17 species of parasites. These comprised 1 myxozoan (Henneguya exilis), 2 copepods (Ergasilus arthrosis and Lernaea cyprinacea), 1 acarine (Oribatida gen. sp.), 1 piscicolid leech (Myzobdella lugubris), 4 monogeneans (Gyrodactylus hoffmani, Gyrodactylus sp., Dactylogyrus extensus, and Ligictaluridus floridanus), 4 nematodes (Contracaecum sp., Eustrongylides sp., Rhabdochona sp., and Truttaedacnitis truttae), 3 cestodes (Bothriocephalus acheilognathi, Corallobothrium fimbriatum, and Megathylacoides giganteum), and 2 trematodes (Ornithodiplostomum sp. and Posthodiplostomum sp.). Rhabdochona sp. was the only adult parasite native to the LCR. Infection intensities of Ornithodiplostomum sp. and B. acheilognathi were positively correlated with length of the humpback chub Gila cypha. Adult helminths showed a high degree of host specificity, except B. acheilognathi, which was recovered from all fish species examined but was most abundant in cyprinids. Abundance of B. acheilognathi in the humpback chub was highest in the fall and lowest in the summer in both reaches of the LCR. There was no major taxonomic difference in parasite assemblages between the 2 different reaches of the river (LC1 and LC2). Parasite community diversity was very similar in humpback chub, regardless of sampling site or time. The parasite fauna of the LCR is numerically dominated by B. acheilognathi and metacercariae of Ornithodiplostomum sp. The richest and most diverse component community occurred in a nonnative species, the channel catfish Ictalurus punctatus, but infracommunity species richness was highest in a native host, humpback chub.     

Potamotrygon marinae n. sp., a new species of freshwater stingrays from French Guiana (Myliobatiformes, Potamotrygonidae)

Six specimens of freshwater stingrays from the French Guiana belonging to the genus Potamotrygon [S.W. Garman, On the pelvis and external sexual organs of selachians, with special reference to the new genera Potamotrygon and Disceus, Proc. Bost. Soc. nat. Hist. 19 (1877) 197-215], do not present characters that are typically shown by species to which they have been attributed. Five belong to a new species here named Potamotrygon marinae n. sp. This species is differentiated from the others by the feebly development of the prepelvic process, the development of the postorbital process as an enlarged blade, the unsegmented angular cartilage, the dorsal surface coloration composed of wide circular patches themselves formed by smaller pale patches, the almost dark coloration of the ventral surface tessellated with pale patches, and the small sized spiny tubercles situated in the middorsal region, before the caudal sting.     

Helminth parasite communities of the conger eel in the estuaries of Arousa and Muros (Galicia, north-west Spain)

The nematodes Cucullanus hians, Cucullanus longispiculum , Cucullanus minutus , Contracaecum sp., Anisakis simplex , and Cristitectus congeri , the cestodes Grillotia , sp. and Scolex pleuronectis , and the acanthocephalan Acanthocephaloides propinquus , were recorded from 251 conger eels from the Muros and Arousa estuaries, north-west Spain. Several species were useful as tags and showed that conger eels in both estuaries and also on the continental shelf belong to separate populations. The nematode C. congeri , shows a distribution pattern indicating that the trophic chains involving the conger eel in each estuary are probably different. The species composition and abundance of the nematode, cestode and acanthocephalan fauna of Conger conger , on the north-west Spanish coast may depend more on population isolation and variations in trophic chains between the sites studied than on the particular environmental conditions of the sites.     

Diversification and species boundaries of Rhinebothrium (Cestoda; Rhinebothriidea) in South American freshwater stingrays (Batoidea; Potamotrygonidae)

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.     

Cytogenetic and molecular characteristics of Potamotrygon motoro and Potamotrygon sp. (Chondrichthyes,Myliobatiformes, Potamotrygonidae) from the Amazon basin: Implications for the taxonomy of the genus

The chromosomes of two freshwater stingrays, Potamotrygon motoro and Potamotrygon sp., from the Amazon River basin in Brazil were investigated using integrated molecular (cytochrome c oxidase subunit 1) and cytogenetic analyses. Potamotrygon motoro presented intraspecific variation in the diploid number, with 2n=66 in the females and 2n=65 in the males, while Potamotrygon sp. had a karyotype with 66 chromosomes, in both sexes. The C-banding revealed the presence of heterochromatic blocks accumulated in the centromeric region of all the chromosomes in both species. The FISH assays with 18S DNA probes highlighted the terminal region of three or four chromosome pairs in P. motoro and seven chromosomes in Potamotrygon sp. The rDNA 5S sequences were found in only one chromosomal pair in both species. The interspecific genetic distance based on the COI sequences, between P. motoro and Potamotrygon sp. from Amazon River was 10.8%, while that between the Amazonian P. motoro and Potamotrygon amandae from the Paraná River was 2.2%, and the genetic distance between Potamotrygon sp. and P. amandae was 11.8%. In addition to the new insights on the cytogenetics of the study species, the results of the present study confirmed the existence of heteromorphic sex-linked chromosomes in P. motoro.     

西藏拉萨河鱼类内寄生蠕虫的种类组成及其群落特征

2004年7月对西藏拉萨河鱼类的体内寄生蠕虫进行了调查,共采集到7种鱼类,其中6种隶属于裂腹鱼亚科,1种隶属于鳅科。在这些鱼类中,共发现了2种棘头虫和1种棘头虫未定种、3种线虫、3种绦虫及异肉吸虫属(Allocreadium)的种类。它们分别是青海新棘吻虫(Neoechinorhynchus qinghaiensis)、裸鲤棘头虫(Echinorhynchus gymnocyprii)和新棘吻虫未定种(Neoechinorhynchus sp.),希蚋杆咽线虫(Rhabdochona hellichi)、对盲囊线虫(Contracaecum sp.)和胃瘤线虫(Eustrongylides sp.),东方短结绦虫(Breviscolex orientalis)、舌状绦虫(Ligula sp.)和裂头绦虫(Diphyllobothrium sp.),以及寄生裂腹鱼的异肉吸虫(Allocreadium spp.)。对青海新棘吻虫、杆咽线虫、东方短结绦虫、异肉吸虫和新棘吻虫未定种在鱼类中发育成熟的寄生虫进行了形态描述。从不同的裂腹鱼中获得的异肉吸虫属的种类未能鉴定到种;其他没有鉴定到种的寄生虫主要是利用鱼类作为中间寄主的种类,其种类鉴定则有赖于成虫的获得。迄今为止,青海新棘吻虫和裂腹鱼异肉吸虫(A.schizothoracis)仅在裂腹鱼类中被发现,可能表明裂腹鱼具有特异性的棘头虫和异肉吸虫。在所检查的7种鱼类中,除异齿裂腹鱼(Schizothorax oconnori)没有发现蠕虫外,其他6种鱼都发现了4~6种蠕虫,显示较高的物种丰富度;5种裂腹鱼蠕虫群落的Shannon-Wiener指数较高(0·6131~1·5434),而细尾高原鳅(Triplophysa stenura)的较低(0·2911);5种裂腹鱼寄生虫群落之间的相似性相对较高,为(0·1732±0·2303)~(0·3751±0·2758),而裂腹鱼与细尾高原鳅的相似性则较低,为(0·0288±0·0877)~(0·0916±0·1618)。在这些寄生蠕虫中,以鱼类为中间宿主的寄生虫种类有4种,他们都以鸟类为终末寄主,因而也在一定程度上反映了该地区的动物区系组成。