Molecular evidence of cryptic diversity in Paracaryophyllaeus (Cestoda: Caryophyllidea), parasites of loaches (Cobitidae) in Eurasia,including description of P. vladkae n. sp.

Molecular phylogenetic analysis of an extensive collection of monozoic tapeworms of the genus Paracaryophyllaeus Kulakovskaya, 1961 (Cestoda: Caryophyllidea), parasites of loaches (Cypriniformes: Cobitidae) in Eurasia, has revealed cryptic species diversity within this long-time monotypic genus, especially in the Paracaryophyllaeus gotoi (Motomura, 1927) species complex [syn. Paracaryophyllaeus dubininorum (Kulakovskaya, 1961); type species]. Three independent, well-supported clades were discovered on the basis of molecular data: (i) specimens from Misgurnus anguillicaudatus and Cobitis lutheri from China, Russian Far East and Japan — called herein P. cf. gotoi 1, which may be conspecific with P. gotoi (Motomura, 1927), although in the absence of sequence data for P. gotoi from its type locality (basin of the River Kumkan in Korea), no certain inferences about their identity can currently be made; (ii) specimens from M. anguillicaudatus from China and Japan — P. cf. gotoi 2, which are morphologically indistinguishable from those of P. cf. gotoi 1; and (iii) morphologically distinct tapeworms from the endemic loach Cobitis bilseli from southwestern Turkey (Beyşehir Lake), which are described herein as a new species. Paracaryophyllaeus vladkae Scholz, Oros and Aydoğdu n. sp. differs from the remaining species of the genus in the following characteristics: the testes begin anterior to the first vitelline follicles (versus posterior), the body is short and robust (versus more elongate and slender), and the scolex is wide, rounded or apically tapered (versus claviform to truncate). Species composition of the genus, host specificity of species and geographical distribution are briefly discussed.     

埃塞俄比亚塔纳湖鲤科鱼类体内亚美尼亚许氏绦虫Khawia armeniaca (Cholodkovsky, 1915) Shulman, 1958 (绦虫纲: 鲤蠢目) 的形态鉴定

在埃塞俄比亚境内塔纳湖中发现了1种寄生于鲤科鱼类: 间魮(Labeobarbus intermedius)和Labeobarbus tsanensis体内的许氏绦虫, 经形态学鉴定其为亚美尼亚许氏绦虫Khawia armeniaca (Cholodkovsky, 1915)(绦虫纲: 鲤蠢目)。该绦虫鉴别特征为头节呈半球状, 边缘光滑, 无皱褶; 睾丸分布区域从虫体中部至阴茎囊之前; 卵巢前卵黄腺分布于虫体中后部至阴茎囊前部区域, 少数排列在阴茎囊之后; 子宫起始于阴茎囊后方弯曲环绕直至卵巢后部区域, 有少许卵黄腺排列在子宫和卵巢的两侧。此外, K. armeniaca卵巢呈滤泡状或蝴蝶状, 雌雄生殖孔分离但彼此距离很近, 开口于体表并形成同一生殖腔, 且雄性生殖孔位于雌性生殖孔前方。卵巢后卵黄腺数目少于100个, 分布于虫体末端, 卵黄腺距离卵巢后翼较远, 部分样品内卵黄腺接近卵巢后翼。     

Morphological and molecular data for larval stages of four species of Petasiger Dietz, 1909 (Digenea: Echinostomatidae) with an updated key to the known cercariae from the Palaearctic

Recent molecular phylogenetic studies on fish tapeworms of the genus Caryophyllaeus Gmelin, 1790 (Cestoda: Caryophyllidea), parasites of cyprinid fishes in the Palaearctic Region, have revealed unexpected phenotypic plasticity that seems to be related to definitive hosts. In the present paper, Caryophyllaeus brachycollis Janiszewska, 1953 is redescribed and its two morphotypes are circumscribed on the basis of newly-collected specimens. Morphotype 1 from barbels [Barbus spp. including the type-host Barbus barbus (L.); Barbinae] and chubs (Squalius spp.; Leuciscinae) is characterised by a more robust body with spatulate scolex, which is only slightly wider than a very short neck region, and the anterior position of the testes and vitelline follicles, which begin immediately posterior to the scolex. Specimens of Morphotype 2 from breams (Abramis spp., Ballerus spp. and Blicca spp.; Abraminae), which have been previously misidentifed as Caryophyllaeus laticeps (Pallas, 1781), possess a more slender body with a flabellate scolex, which is much wider than a long neck, and the first testes begin at a considerable distance posterior to the first vitelline follicles. Despite conspicuous differences in the scolex morphology and the anterior extent of the testes and vitelline follicles, both morphotypes are identical in the morphology of the posterior end of the body, in particular that of the cirrus-sac, which is large, thick-walled, elongate-pyriform, and contains a long cirrus, and in the distribution of the vitelline follicles, which surround medially vas deferens near the cirrus-sac. A specimen of Morphotype 1 from B. barbus from the Argens River, France, is designated as neotype of C. brachycollis. The presence of phenotypic plasticity in morphological characteristics previously used for differentiation of species of Caryophyllaeus may confound species identification, which is crucial for biodiversity, ecological and evolutionary studies. To avoid these potential problems, combination of morphological and molecular data is strongly recommended.     

A new species of Neohaematotrephus (Digenea: Echinostomiformes: Cyclocoelidae) in the spotted-sandpiper Actitis macularia (Charadriiformes: Scolopacidae) from Venezuela

Fischthal and Nasir (1974) reported Neohaematotrephus brasilianum (as Cyclocoelum brasilianum) in the spotted-sandpiper Actitis macularia from Venezuela. Three voucher specimens from that report, deposited in the United States National Parasite Collection, however, differ from N. brasilianum by having the cirrus sac on the sinistral side of the body, which resembles N. facioi, N. arayae, and N. gendrei. The new species is similar to N. brasilianum by having vitelline follicles extending well anterior to the intestinal bifurcation and by having a short and laterally displaced cirrus sac whose posterior end does not reach the intestinal bifurcation, whereas all other members of Neohaematotrephus have a cirrus sac that is medially oriented. Neohaematotrephus gendrei and N. facioi have cirrus sacs that extend to the level of the intestinal bifurcation, and N. arayae has a cirrus sac that extends well posterior to the posterior margin of the ceca. By having the ovary on the sinistral side of the body, the new species is similar to N. brasilianum, N. gendrei, and N. arayae but differs from N. facioi, in which the ovary is dextral.     

Whallwachsia illuminata n. gen., n. sp. (Trematoda: Digenea: Plagiorchiformes: Prosthogonimidae) in the steely-vented hummingbird Amazilia saucerrottei (Aves: Apodiformes: Trochilidae) and the yellow-olive flycatcher Tolmomyias sulphurescens (Aves: Passeriformes: Tyraninidae) from the Area de Conservación Guanacaste, Guanacaste, Costa Rica

A new species of digenean found in the intestines of the steely-vented hummingbird Amazilia saucerrottei and the yellow-olive flycatcher Tolmomyias sulphurescens from the Area de Conservación Guanacaste, Guanacaste, Costa Rica, resembles members of the Prosthogonimidae in having a highly lobate ovary; an elongate cirrus sac containing the cirrus, pars prostatica, and internal seminal vesicle; no external seminal vesicle; 2 fields of extracecal vitelline follicles restricted to the area between the intestinal bifurcation and testes; and uterine loops occupying all available space in the hind body. The new species differs from all other members of the family in having genital pores opening laterally to the cecum, immediately anterior to the acetabular level, and markedly oblique rather than symmetrical testes. Consequently, we propose the new genus Whallwachsia for the species. Preliminary phylogenetic assessment suggests that the species is the sister group of all other prosthogonimids.     

Neohaematotrephus arayae n. sp. (Digenea: Echinostomiformes: Cyclocoelidae) in Jacana spinosa (Aves: Charadriiformes: Jacanidae) from the Area de Conservación Guanacaste, Costa Rica

Specimens of a species of cyclocoelid digenean inhabiting Jacana spinosa from the Area de Conservación Guanacaste, Costa Rica, most closely resemble Haematotrephus facioi (Brenes and Arroyo, 1962) Yamaguti, 1971, in the same host from Aranjuez, Puntarenas Province, Costa Rica, in having confluent vitelline follicles posteriorly, diagnostic of Neohaematotrophus, and in pharynx length, ovary width, and cirrus sac on the sinistral side. The new species is also highly similar in appearance to H. gendrei Dubois, 1959, also inhabiting a jacanid (from West Africa), which has vitelline follicles confluent posteriorly, and extending anteriorly to the intestinal bifurcation and genital pore opening immediately posterior to the anterior margin of the pharynx. Like H. facioi, H. gendrei has a relatively much shorter and broader cirrus sac than does the new species. Examination of the holotype and paratype of H. facioi confirmed that the specimens from Guanacaste differ in having a longer body, a larger ovary and eggs, and smaller testes. They also have the ovary on the sinistral rather than the dextral side of the body, genital pore anterior to the pharynx rather than at or posterior to the level of the posterior margin of the pharynx, longer and thinner cirrus sac, and eggs without eyespotted miracidia. Half the eggs in both specimens of H. facioi have well-developed eyespotted miracidia, whereas the typical condition for cyclocoelids is for virtually all eggs to exhibit eyespotted miracidia. Both H. facioi and H. gendrei are transferred to Neohaematotrophus, along with the new species.     

A new species of Petasiger (Digenea: Echinostomiformes: Echinostomatidae) in the brown pelican, Pelecanus occidentalis, (Aves: Pelecaniformes: Pelecanidae), from the Area de Conservación Guanacaste, Costa Rica

A new species of Petasiger inhabits Pelecanus occidentalis, from the Area de Conservación Guanacaste, Costa Rica. The new species most closely resembles Petasiger novemdecim Lutz 1929 and Petasiger caribbensis Nassi, 1980 by having 19 circumoral spines and vitelline follicles confluent between the ventral sucker and gonads. The new species differs from both of these species by having a cirrus sac that is anteroposteriorly elongate and that reaches posteriorly to the midventral sucker, an ovary and Mehlis' gland that overlap the anterior testis dorsally, a uterus that lies dorsal to the ventral sucker, and a dextromedial genital pore. In P. novemdecim and P. caribbensis the cirrus sac is round and does not extend posteriorly to the anterior margin of the ventral sucker, both the ovary and Mehlis' gland are anterior to the anterior testis, the uterus runs lateral to and not dorsal to the ventral sucker, and the genital pore opens medially and sinistromedially, respectively.     

A new monozoic tapeworm, Lobulovarium longiovatum n. g., n. sp. (Cestoda: Caryophyllidea), from barbs Puntius spp. (Teleostei: Cyprinidae) in the Indomalayan region

A new caryophyllidean cestode is described from barbs Puntius spp. (Cypriniformes: Cyprinidae), with P. sophore (Hamilton) as its type-host, in the Ganges and Brahmaputra river basins in India and Bangladesh, and a new genus, Lobulovarium n. g., is proposed to accommodate it. The genus belongs to the Lytocestidae because its vitelline follicles are situated in the cortex. It is typified by: (i) a peculiar ovary, which is roughly H-shaped, but with asymmetrical, irregular lobes on its ventral and dorsal sides; (ii) an extensive vitellarium formed by numerous vitelline follicles scattered throughout the cortex; (iii) a long, conical postovarian part of the body with numerous vitelline follicles; (iv) a broadly digitate scolex with a slightly protrusible central cone; (v) a single gonopore (male and female genital ducts open via a single pore and a common genital atrium is absent); and (vi) a small number of testes (< 60). Molecular data (partial sequences of the lsrDNA) indicate that Lobulovarium longiovatum n. sp. belongs among the most basal caryophyllidean cestodes, being unrelated to species from siluriform catfishes in the Indomalayan region. Paracaryophyllaeus osteobramensis (Gupta & Sinha, 1984) Hafeezullah, 1993 (syn. Pliovitellaria osteobramensis Gupta & Sinha, 1984) from another cyprinid fish, Osteobrama cotio (Hamilton), in Uttar Pradesh, India, is tentatively transferred to Lobulovarium as L. osteobramense (Gupta & Sinha, 1984) n. comb. It differs from L. longiovatum by having much smaller eggs (length <50 μm versus >90 μm in L. longiovatum), which are spherical (length/width ratio 1:1 versus 2.5-3:1 in the new species), and the presence of vitelline follicles alongside the ovarian lobes (almost completely absent in L. longiovatum).     

Two new species of Nomimoscolex (Cestoda: Proteocephalidea,Monticelliidae) from Gymnotus carapo (Pisces: Gymnotiformes) in Argentina

Nomimoscolex guillermoi n. sp. and N. dechambrieri n. sp. are described from the gymnotiform fish Gymnotus carapo from Argentina. The new species are placed into Nomimoscolex based on the cortical position of the vitelline follicles, and medullary position of the testes, ovary, and uterus. Both species were compared to the 13 species considered valid in the genus. The combination of features distinguishing N. guillermoi from N. dechambrieri is (1) the position of the vagina to cirrus pouch (anterior or posterior vs always anterior respectively), (2) the total number of testes (41-85 vs 108-130 respectively), (3) the distribution of the vitelline follicles (arranged in dorso-lateral and ventro-lateral bands vs lateral bands respectively), (4) the length of the uteroduct (ending 58% vs 35% from posterior margin of mature proglottis respectively), and (5) the presence of gland cells in the scolex (unicellular glands in the apical region and the external margin of suckers vs the presence of unicellular glands in the apex and other grouped in a cluster medially to the suckers respectively).     

Steganoderma szidati n. sp. (Trematoda: Zoogonidae) from Galaxias maculatus (Jenyns) and G. platei Steindachner in Patagonia,Argentina

Steganoderma szidati n. sp. is described from the intestine of two freshwater fishes, Galaxias maculatus and G. platei (Galaxiidae), from Andean lakes in Patagonia, Argentina. This freshwater zoogonid species fits in the genus Steganoderma (sensu Bray, 1987) because of the length of the caeca and the position of the vitelline follicles. The new species is characterised by possesing 6-13 vitelline follicles situated between the anterior margin of the ventral sucker and the poterior margin of the testis. The gonads are in the anterior hindbody and the ovary is anterior to the right testis. The cirrus has two conspicuous spines at its distal end, and the seminal vesicle always exhibits a constriction. The excretory vesicle never reaches the level of the posterior margin of the testes.     

Taxonomic status of cestodes of the genus Paracaryophyllaeus Kulakowskaja, 1961 (Caryophyllidea: Caryophyllaeidae)

A taxonomic revision of cestodes of the genus Paracaryophyllaeus Kulakowskaja, 1961, parasites of cobitid fishes, has been performed. Three species (Paracaryophyllaeus gotoi (Motomura, 1927), P. kulakowskae sp. n., and P. misgurni sp. n.) are considered valid species; two are described as new species. P. dubininorum Kulakowskaja, 1961 is a young synonym of P. gotoi. The taxonomic status for P. gotoi sensu Scholz, 1989, P. gotoi sensu Scholz et al., 2001, and Paracaryophyllaeus sp. 1 and Paracaryophyllaeus sp. 2 (described in present work) needs specification.     

Galaxitaenia toloi n. gen., n. sp. (Eucestoda: Pseudophyllidea) from Galaxias platei (Pisces: Osmeriformes, Galaxiidae), in the Patagonian region of Argentina

Galaxitaenia n. gen. (Eucestoda: Pseudophyllidea) is proposed to accommodate Galaxitaenia toloi n. gen., n. sp. from Galaxias platei, a freshwater fish inhabiting Andean lakes in Argentine Patagonia. Galaxitaenia belongs to the Triaenophoridae because it possesses a marginal genital pore, a ventral uterine pore, and a follicular vitelline gland. The new genus can be distinguished from other triaenophorids by the following combination of characters: a scolex with a prominent rectangular apical disc without hooks, grooves, or indentations; neck present; segments wider than long to quadrangular; testes in 2 lateral fields, often connected anteriorly; cirrus unarmed; an ovary situated posteriorly; a vagina posterior to the cirrus sac; vitelline follicles medullary, in 2 ventral fields forming 2 wings interrupted medially; a uterus saccate to branched; and eggs without operculum. The types, distribution, and density of microtriches were analyzed on the surface of the tegument of scolex, neck, and immature segments. The presence of tumuli were observed on the apical disc of the scolex. Galaxitaenia toloi n. sp. is the first triaenophorid species recorded in a South American freshwater fish and the fourth helminth parasitizing the intestine of G. platei.     

A new genus and species of proteocephalidean tapeworm (Cestoda) from Pangasius larnaudii (Siluriformes: Pangasiidae) in Southeast Asia

A new proteocephalidean cestode is described from spot pangasius, Pangasius larnaudii (Siluriformes: Pangasiidae), from Tonle Sap Lake in Cambodia and a new genus, Pangasiocestus , is proposed to accommodate it. The genus is placed in the Gangesiinae because its scolex possesses a large rostellum-like apical organ and its genital organs (testes, ovary, vitellarium, and uterus) are situated in the medulla, with some vitelline follicles paramuscular. Pangasiocestus romani n. gen. and n. sp., the type and only species of the new genus, is characterized mainly by its rosette-like scolex composed of 4 lobes bearing a small sucker in their center, and the apical part with a large, discoidal, rostellum-like apical organ devoid of hooks, by weakly developed inner longitudinal musculature formed by very few isolated muscle fibers, uneven size of testes in immature and mature proglottids, with lateral testes smaller and more dense than median ones, by very narrow lateral bands of vitelline follicles, formed usually by single follicles, and by the vagina anterior to the cirrus sac. This is the first proteocephalidean cestode from a pangasiid catfish identified to the species level (proteocephalidean cestodes from 3 Pangasius spp. reported in an unpublished account from Vietnam, misidentified as Proteocephalus osculatus (Goeze, 1782) [?= Glanitaenia osculata ], are not considered).     

Nomimoscolex semenasae n sp (proteocephalidea: Monticelliidae), a cestode parasite of Diplomystes viedmensis (Pisces: Siluriformes) from the Patagonian region of Argentina

Nomimoscolex semenasae n. sp. is described from the primitive fish Diplomystes viedmensis (Siluriformes) from the Patagonian region of Argentina. The new species is placed in Nomimoscolex because of the cortical position of the vitelline follicles, medullary position of the testes, ovary and uterus, and having a scolex with four uniloculate suckers. N. semenasae differs from all other species in the genus by the following combination of characters: (1) apical organ absent; (2) strobila acraspedote; (3) vagina anterior or posterior to cirrus-sac and lacking a sphincter; (4) testes in one irregular layer and in two fields connected anteriorly; (5) uterine stem cortical in immature proglottides, growing from cortical stem into medullary region in mature proglottides; (6) long uteroduct; and (7) presence of spiniform microtriches on all regions of the scolex, proliferation zone and immature proglottis. This is the first record of a proteocephalidean tapeworm in D. viedmensis and in the family Diplomystidae.     

A new species of Paracreptotrema (Digenea,Plagiorchiformes, Allocreadiidae) infecting two species of poeciliids in Río Malila of the Río Pánuco basin,Hidalgo, México,with a key to the species of the genus

Paracreptotrema rosenthali sp. n. was discovered in the intestine of Xiphophorus malinche and Pseudoxiphophorus jonesii, collected from the headwaters of Río Malila, tributary of Río Conzintla, in the Río Pánuco basin, Hidalgo, México, during 2008–2009. The new species differs from the five known species of Paracreptotrema Choudhury, Pérez-Ponce de León, Brooks & Daverdin, 2006 by having vitelline follicles that extend from a level anterior to the pharynx to mid-testes, the seminal vesicle which is more extensively folded, and a wider cirrus sac. The new species resembles Paracreptotrema heterandriae in the length of its ceca, which surpasses the posterior margin of the ovary but do not reach the testes. A key to the species of Paracreptotrema is provided.     

<Emphasis Type="Italic">Monticellia santafesina</Emphasis> n. sp. (Cestoda: Proteocephalidea), a parasite of <Emphasis Type="Italic">Megalonema platanum</Emphasis> (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin,Argentina

The proteocephalidean tapeworm Monticellia santafesina n. sp. is described from the siluriform catfish Megalonema platanum (Günther) (Siluriformes: Pimelodidae) in the Paraná River basin, Argentina. The new species is allocated to Monticellia La Rue, 1911 (Proteocephalidae: Monticelliinae) because of the cortical position of the testes, ovary, vitelline follicles and uterus, a globular scolex without a metascolex and uniloculate suckers. The new species differs from all other species of Monticellia (except for M. lenha Woodland, 1933) in possessing a vaginal canal opening anterior or posterior to the cirrus-sac. M. santafesina can be distinguished from M. lenha by the following characteristics: a larger body size; a weakly developed internal longitudinal musculature arranged in 15–35 slim bundles of muscle fibres; vitelline follicles not interrupted at the level of the cirrus-sac and vaginal canal, and with a few paramuscular and/or medullary follicles; the absence of large spinitriches on the anterior margin of the suckers; and the utilisation of Megalonema platanum (in the Paraná River basin) as its host, rather than Sorubimichthys planiceps (Spix & Agassiz) (in the River Amazon). Monticellia santafesina exhibits low values of prevalence (9%) and intensity of infection (1). Megalonema platanum was parasitised by two proteocephalidean cestodes, Rudolphiella cf. lobosa (Riggenbach, 1895) and the new species described in this paper.     

Resurrection and emendation of Pseudoparamacroderoides Gupta & Agrawal, 1968 (Digenea: Macroderoididae), description of a new species from Vietnam,and comments on the systematics of macroderoidid genera

We herein resurrect and emend Pseudoparamacroderoides Gupta & Agrawal, 1968 (Digenea: Macroderoididae) and describe a new species, Pseudoparamacroderoides dongthapensis n. sp., from adult specimens infecting the intestine of a riverine catfish, Mystus mysticetus Roberts, (Siluriformes: Bagridae) in the Mekong River, Vietnam. Pseudoparamacroderoides (Pseudoparamacroderoides seenghali Gupta & Agrawal, 1968 [type species]; Pseudoparamacroderoides vittati Kakaji, 1969 [= Ps. vittatusi]; Pseudoparamacroderoides raychaudhurii Agarwal & Kumar, 1983; and Pseudoparamacroderoides keni Agarwal & Agarwal, 1984) differs from other macroderoidid genera by having the combination of a subspherical oral sucker that lacks distinctly-enlarged circumoral spines; caeca that extend posteriad beyond the testes without forming a cyclocoel; testes that are approximately ≤1/3 maximum body width in diameter; a cirrus sac that is claviform, slightly dorsal to and predominantly lateral to the ventral sucker (cirrus sac partially dorsolateral to dextral or sinistral margin of ventral sucker); symmetrical vitelline fields that extend posteriad to the middle of the post-testicular space (not restricted to the inter-gonadal space) and that remain separate (not confluent) anteriorly and posteriorly; and an excretory vesicle that is I-shaped (with or without anterior swelling) and wholly post-ovarian, inter-testicular, or median to the posterior testis. Pseudoparamacroderoides dongthapensis n. sp. differs from its congeners by having an elongate hindbody (>2× forebody length) and an excretory vesicle that is approximately half as long as the body and that extends anteriad beyond the anterior testis. This is the first record of a species of Pseudoparamacroderoides from beyond the Indian sub-continent, from M. mysticetus, and from the Mekong River or from Vietnam. A diagnostic key to macroderoidid genera and a key to Pseudoparamacroderoides spp. are provided.

     

Onchobothrium malakhovi n. sp. (Cestoda: Onchoproteocephalidea) ex Bathyraja (Arctoraja) sexoculata (Rajiformes: Arhynchobatidae) from Kuril Islands (Russia), with comments on the status of the genus Onchobothrium

Onchobothrium malakhovi n. sp. was found in the spiral valve of the softnose skate Bathyraja (Arctoraja) sexoculata off the Simushir Island (Kuril Islands, Russia). The new species has bothridia with three loculi and no additional suckers on bothridia, single-toothed hooks unconnected by their bases, no spines at the bases of the hooks, dense matrix around the hook bases shaped as an unpaired butterfly wing, and a short and wide ovary. Onchobothrium malakhovi n. sp. differs from O. antarcticum and O. magnum in having a smaller total length, cirrus sac and ovary, smaller testes and eggs. Additionally, the new species differs from O. antarcticum by the absence of a vaginal sphincter and shorter bothridia; differs from O. magnum in having fewer proglottids and smaller vitelline follicles. It differs from O. farmeri, O. convolutum, and O. pseudouncinatum, by the absence of a small spine at the base of the hooks and the absence of accessory suckers on bothridia; from O. pseudouncinatum, additionally, by unconnected hooks; from O. schizacanthium, by the number of testes and by the presence of a postvaginal group of testes. Onchobothrium malakhovi n. sp. was placed among other members of the Onchoproteocephalidea with a high support based on the sequence data for the D1-D3 region of the 28S rDNA and cox1 gene. The phylogenetic position of the genus Onchobothrium sensu lato remains ambiguous. We suggest that Onchobothrium sensu lato is a complex genus containing at least two morphologically different groups of species. Onchobothrium farmer, O. convolutum, O. schizacanthium, and O. pseudouncinatum, for which there are no molecular genetic data, are considerably different morphologically from O. malakhovi n. sp., O. antarcticum, and O. magnum. A new genus might have to be established for the latter three species after the accumulation of genetic data.     

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.