Two new species of Monopisthocotyla (Dactylogyridea: Dactylogyridae) parasitizing the nasal cavities of Bryconops melanurus (Characiformes: Iguanodectidae) from coastal drainages of the Eastern Amazon, Brazil.

The present study integrates molecular and morphological data to support the proposal of new species of Telethecium Kritsky, Van Every & Boeger, 1996 and Diaphorocleidus Jogunoori, Kritsky & Venkatanarasaiah, 2004 from the nasal cavities of Bryconops melanurus (Bloch) of the coastal drainages of the Eastern Amazon. Telethecium tiquira sp. n. is characterized by possessing a male copulatory organ (MCO) with two circular sclerotized brims on the base, a coiled tubular shaft having 1 counterclockwise rings, an accessory piece with enlarged base, pincer-shaped at the distal portion; a sclerotized calyx-shaped vaginal vestibule, and hooks with proximal shank dilatation comprising 3/4 of the shank length. Also, Telethecium tiquira sp. n. can be easily distinguished from other species of the genus by the absence of a protruding bag located at the level of the copulatory complex. Diaphorocleidus forficata sp. n. is characterized by having a MCO with two counterclockwise rings, circular sclerotized tandem brim associated with the base of the MCO; accessory piece non-articulated with the MCO, bifurcate, pincer-shaped; vaginal pore sinistral-ventral with opening marginal, vaginal canal sclerotized, elongated, comprising one loop in the proximal portion before entering to the seminal receptacle; ventral anchor with shaft elongated and evenly curved on the axis; point short and slightly curved, and hooks similar in shape and size, hooks with proximal dilatation comprising approximately of the shank length. Furthermore, D. forficata sp. n. is supported by phylogenetic analysis based on sequences of the partial 28S rDNA gene, which placed D. forficata sp. n. in a well-supported clade of Diaphorocleidus spp. of characiform fishes. Thus, the two new species described here expand our knowledge about the diversity of monopisthocotylan parasites from the nasal cavities of Neotropical fishes. The findings of this study provide valuable insights into the biodiversity of the region and highlight the importance of further research in this area.

Diversification processes between monogenoids (Dactylogyridae) and their marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Due to their high specificity, monogenoids from fish provide an interesting model to study historical associations of hosts and parasites. High agreement between host and parasite phylogeny is often interpreted as evidence of cospeciation. However, cophylogenetic signal may also arise from other, either adaptive or non-adaptive, processes. We applied the recently developed Cophylospace Framework to better understand the evolutionary relationship between monogenoids and marine catfish from the Atlantic coast of South America. The associations between 12 marine catfish and 10 monogenoid species were assessed. Molecular data of host and parasite species were used for phylogenetic reconstruction. We used anchor morphology based on Procrustes coordinates to evaluate whether closely related hosts are associated with morphologically similar parasites. To assess the association between parasite phylogeny and host morphology, we produced a distance matrix based on morphological characters of catfishes. Agreement between phylogenies and between phylogeny and morphology was measured using Procrustes R2 computed with PACo. The parasite phylogeny obtained in this study represents the first complete phylogenetic hypothesis of monogenoids parasitizing ariids from South America. The Cophylospace analysis suggested that phylogenetic and morphological distance of monogenoids contributes similarly to explain the pattern of host­parasite associations, whereas parasite phylogeny is more strongly associated with the morphological traits of the hosts than with host phylogeny. This evidence suggests that cospeciation is not a major force accounting for diversification in the monogenoids studied. Rather host morphological traits seem to be a more important driver, which conforms with evidence from other host‒monogenoid systems.

Morphological and molecular characterization of Ameloblastella pirarara sp. n. (Monogenoidea: Dactylogyridae) parasitizing the large Amazonian catfish Phractocephalus hemioliopterus.

In this study, integrative taxonomy is applied to describe a new dactylogyrid species, Ameloblastella pirarara sp. n. from the gills of Phractocephalus hemioliopterus, a commercially and ecologically important Amazonian catfish. Ameloblastella pirarara sp. n. can be distinguished from its congeners mainly by the morphology of the male copulatory organ (MCO), accessory piece, and anchors. The new species most resembles Ameloblastella unapi, from the Peruvian Amazon, but differs from it by the number of MCO rings, morphology of the vaginal canal and sclerotized structures of the haptor. Phylogenetic analyses based on sequences of the partial 28S rDNA (D1-D2 domains) gene placed the new species in a well-supported subclade of Ameloblastella spp. parasites of Neotropical siluriform fish, as a sister taxon to Ameloblastella unapioides. Thus, the new species described herein expands our knowledge of the diversity of monogenoid parasites from Amazonian freshwater fish.

Morphological and molecular characterization of Udonella brasiliensis n. sp. (Monogenoidea), an epibiont on Caligus sp. parasite of Ariidae from the southeastern coast of Brazil.

The present study describes Udonella brasiliensis n. sp., an epibiont found on Caligus sp., a parasite the ariids Genidens barbus (Lacepède) and Aspistor luniscutis (Valenciennes), caught on the coast of the state of São Paulo, Brazil. Morphological and molecular analyses (partial 18S rDNA) were carried out. The morphological data showed that U. brasiliensis n. sp. can be distinguished from current valid species by its morphometric attributes (e.g., body, pharynx, ovary and testis), while the molecular information supports the proposal of a new species. The 18S rDNA phylogenetic analysis shows a close relationship between the new species and Udonella australis Carvajal & Sepulveda, in a subclade formed of species that parasitize South American fish. Finally, this study also discusses a scenario of initial irradiation for udonellids.

An integrative taxonomic study of Susanlimocotyle narina n. gen. n. sp. (Monogenoidea, Dactylogyridae) from the nasal cavities of a marine catfish (Siluriformes, Ariidae) from the Atlantic Amazon Coast of Brazil and new molecular data of Chauhanellus spp.

Based on a taxonomic approach, combining morphological characters with DNA sequences (i.e.,18S rDNA, ITS1, 5.8S rDNA and ITS2), Susanlimocotyle n. gen. is proposed to accommodates Susanlimocotyle narina n. sp. from the nostrils of the ariid Sciades herzbergii (Bloch) from the coast of the state of Pará, Brazil. Susanlimocotyle n. gen. is characterized by species possessing: an intestinal ceca confluent posteriorly; a male copulatory organ, comprising a variable tube, articulated with the accessory piece; a sclerotized vagina, vaginal aperture dextro-ventral; an onchium; a robust ventral bar; two dorsal bars; a ventral anchor with elongated shaft and a dorsal anchor with deep root expanding into wings. In addition, new molecular data of Chauhanellus spp. are also provided and used for the evaluation of the phylogenetic relationships among monogenoids parasitizing siluriforms. Susanlimocotyle n. gen. exhibited a higher genetic divergence level for 18S rDNA (4.6 to 7.2% [83-130 bp]) with respect to Chauhanellus spp. despite sharing S. herzbergii as a host, than Hamatopeduncularia spp., (4.1 to 5.8% [75-110 bp]) from Oriental ariids. For the 18S rDNA, 5.8S rDNA, ITS1 and ITS2 regions, C. boegeri and C. susamlimae were observed to have the smallest interspecific distances, and C. velum was revealed to be the most genetically distant species to Chauhanellus. The proposal for Susanlimocotyle n. gen. is also supported by phylogenetic analysis based on the 18S rDNA gene, which supports the close relationship between the new genus and Hamatopeduncularia and Chauhanellus from ariids from the South America and Oriental regions. Moreover, the patterns towards the shared diversification between monogenoids and their ariid hosts were addressed.

New species of Anacanthorus (Dactylogyridae: Anacanthorinae) from the gills of Hoplerythrinus unitaeniatus and Erythrinus erythrinus (Characiformes: Erythrinidae) of the coastal drainage in the Eastern Amazon, Brazil.

Species of Anacanthorus are described from the gills of Hoplerythrinus unitaeniatus and Erythrinus erythrinus of drainage systems in the Northeastern Pará State, Brazil. Anacanthorus scyphophallus sp. n. has a male copulatory organ (MCO) with two small flaps in the distal portion; hooks with proximal shank dilatation comprising ½ of the shank length. Anacanthorus ataidei sp. n. has an elongated MCO, with ribbon-like ornaments; hooks without proximal shank dilatation. Anacanthorus siphonocommus sp. n. has an MCO with aculeiform ornaments in the distal portion; hooks with proximal dilatation in the shank comprising ½ of the shank length. Anacanthorus maratininguensis sp. n. has an MCO with a small projection in the form of a hook in the distal region; hooks with proximal dilatation comprising ½ of the shank length. Anacanthorus lacinimentulatus sp. n. has an MCO with extrovert flap skirting its distal region; shank of hooks with proximal dilatation comprising ½ of the total shank length. Anacanthorus cururutuiensis sp. n. presents an MCO with flexed lateral flap in the distal region; hooks with proximal dilatation in the shank comprising » of the shank length. Anacanthorus circumspatulatus sp. n. has an MCO with ornaments in the form of pointed and interleaved blades; hooks with proximal shank dilatation comprising approximately ½ of the shank length. Anacanthorus acrophallus sp. n. has MCO with a small pointed sinistral flap; hooks with proximal dilatation in the shank comprising 1/3 of the shank length. The host-parasite diversity scenario and specificity of Anacanthorus species regarding their characiform hosts are also discussed in this study.

Monogenoids (Polyonchoinea, Dactylogyridae) from Hydrolycus armatus (Characiformes, Cynodontidae) with the description of a new species of Rhinoxenus and the proposal of a new genus from the Xingu River, Pará, Brazil.

One new species of Rhinoxenus Kritsky, Boeger & Thatcher, 1988 from the nasal cavities and four new species of Mymarothecioides n. gen. from the gills are described in Hydrolycus armatus (Jardine & Schomburgk). They were collected in the Xingu River, Pará, Brazil. Rhinoxenus cachorra n. sp. is characterized by having a ventral anchor with inconspicuous roots, and point with fish-hook-like termination; copulatory complex comprising a spiraled male copulatory organ (MCO) with two counterclockwise coils, and an accessory piece with an expanded, bifurcated distal portion. Mymarothecioides n. gen. is proposed and characterized for species without eyes, with or without accessory chromatic granules; copulatory complex comprising articulated MCO, accessory piece; MCO a broad arcuate tube; an accessory piece with a hooked termination in the distal portion; a dextro or midventral non-sclerotized vagina; an anteromedial projection on the ventral bar. Mymarothecium whittingtoni Kritsky, Boeger & Jégu, 1996 is transferred to Mymarothecioides n. gen. as Mymarothecioides whittingtoni (Kritsky, Boeger & Jégu, 1996) n. comb.

An integrative taxonomic study of Pavanelliella spp. (Monogenoidea, Dactylogyridae) with the description of a new species from the nasal cavities of an Amazon pimelodid catfish.

The present study is an integrative taxonomic analysis of Pavanelliella spp. (Monogenoidea, Dactylogyridae), and describes a new species from the nasal cavities of the Amazonian pimelodid catfish Brachyplatystoma rousseauxii (Siluriformes Pimelodidae) from the Tapajós River (Amazon Basin, Pará state, Brazil). Pavanelliella jarii sp. n. is characterized by the presence of 3-4 rings in the male copulatory organ, the absence of rings around the vaginal atrium and by its sinuous vaginal canal, which sometimes forms 0.5-1 rings in the distal portion. The sequencing of the small subunit ribosomal DNA (ssrDNA) and internal transcribed spacer 1 (ITS-1) of three species of Pavanelliella, Vancleaveus cicinnus, and an undetermined dactylogyrid allowed the phylogenetic reconstruction of these dactylogyrids. The analysis indicated that P. jarii sp. n. is closely related to Pavanelliella takemotoi and Pavanelliella pavanellii, which formed a sister clade to ancylodiscoidines parasites of siluriform fish from the Oriental and Afrotropical regions. The analysis also corroborated the non-monophyly of Ancyrocephalinae, revealing that ancylodiscoidines arose between ancyrocephalines lineages, in a sister relationship to pseudodactylogyrines+marine ancyrocephalines+ancyrocephalines parasites of afrotropical perciforms+dactylogyrines. Cladistical analysis indicates that the haptoral anchor/bar complex has been lost several times in the evolutionary history of Dactylogyridae. The analysis also indicated that Dactylogyrus is polyphyletic, as Acolpenteron ureteroecetes and Dactylogyroides longicirrus arose between the three lineages formed by Dactylogyrus spp.

Monogenoidea (Polyonchoinea: Dactylogyridae) parasitizing the gills of marine catfish (Siluriformes: Ariidae) inhabiting the Atlantic Amazon Coast of Brazil.

A parasitological survey of monogenoids infesting the gills of marine catfish (Ariidae) captured from the Atlantic coastal region of the Amazon Basin was carried out during the 2011-2013 period. The gills of 448 specimens involving twelve ariid species (29 Amphiarius rugispinis (Valenciennes), 52 Aspistor quadriscutis (Valenciennes), 74 Bagre bagre (Linnaeus), 16 Cathorops arenatus (Valenciennes), 13 Cathorops agassizii (Eigenmann & Eigenmann), 17 Cathorops spixii (Agassiz), 3 Cathorops sp., 13 Notarius grandicassis (Valenciennes), 14 Sciades couma (Valenciennes), 64 Sciades herzbergii (Bloch), 48 Sciades parkeri (Traill), 13 Sciades passany (Valenciennes), 92 Sciades proops (Valenciennes) were sampled. No monogenoids were found in Cathorops agassizi, Cathorops arenatus, Cathorops spixii, Cathorops sp. and Sciades parkeri, but the gills of the other sampled species were parasitized by at least one species of monogenoid. We identified four new species of Chauhanellus and one new species of Hamatopeduncularia: Chauhanellus hamatopeduncularoideum n. sp. from Amphiarius rugispinis and Sciades couma; Chauhanellus hypenocleithrum n. sp. from Sciades proops; Chauhanellus susamlimae n. sp. from Sciades herzbergii and Sciades passany; Chauhanellus velum n. sp. from Sciades couma, Sciades herzbergii and Sciades passany; and Hamatopeduncularia cangatae n. sp. from Aspistor quadriscutis and Notarius grandicassis. Four previously described species were reported for the first time parasitizing ariids from Atlantic Amazon: Chauhanellus neotropicalis Domingues & Fehlauer, 2006 from Amphiarius rugispinis, Aspistor quadriscutis, Notarius grandicassis and Sciades passany; Chauhanellus boegeri Domingues & Fehlauer, 2006 from Sciades couma and Sciades herzbergii; Hamatopeduncularia bagre Hargis, 1955 from Bagre bagre; and Neomurraytrematoides proops Zambrano & Añez 1993 from Sciades passany. The monotypic Neomurraytrematoides Zambrano & Añez 1993 was placed in synonymy with Neotetraonchus Bravo-Hollis, 1968 and its type-species, Neomurraytrematoides proops Zambrano & Añez 1993 was transferred to Neotetraonchus as Neotetraonchus proops (Zambrano & Añez 1993) n. comb. The morphology of the haptoral structures supports the transfer of Rhamnocercus seenghali Kumar, 2013 to Chauhanellus as Chauhanellus seenghali (Kumar, 2013) n. comb.

Proposal of Whittingtonocotyle n. gen. (Dactylogyroidea: Dactylogyridae), with the description of two new species from the gills of Hoplerythrinus unitaeniatus (Characiformes: Erythrinidae) in Brazil.

Whittingtonocotyle n. gen. is proposed for species with a male copulatory organ sclerotized, spiral, clockwise, non-articulated to the accessory piece; prostatic reservoir separated into two/three zones with one or two terminal areas densely stained; vaginal opening dextrodorsal; anchors without well-defined roots; and dorsal bar with anteromedial protuberance. Two new species of Whittingtonocotyle n. gen. are described from the gills of Hoplerythrinus unitaeniatus (Agassiz), from two rivers of the State of Pará, Brazil. Whittingtonocotyle caetei n. sp. (type species) is characterized by possessing ventral anchor with deep root truncate; prostatic reservoir separated into two zones with one terminal area densely stained; and vaginal canal heavily sclerotized, coiled and dilate distally. Whittingtonocotyle jeju n. sp. is distinguished from the previously species mainly by having a male copulatory organ comprising a coil of about 19 rings (29 rings in Whittingtonocotyle caetei n. sp.); a prostatic reservoir separated into three zones with two terminal areas densely stained; vaginal canal sclerotized, sigmoid; and dorsal bar with short anteromedial process (elongate in Whittingtonocotyle caetei n. sp.).

A new species of Unilatus (Platyhelminthes: Monogenoidea) from the gills of Leporacanthicus galaxias Isbrücker et Nijssen (Siluriformes: Loricariidae) from Brazil.

Unilatus irae sp. nov. (Dactylogyridae) is described from the gills of the armored catfish, Leporacanthicus galaxias Isbrücker et Nijssen (Loricariidae: Ancistrinae), from Guamá river, Pará State, Brazil. The new species can be differentiated from its cogeneners by the combination of the following features: anterior anchor with well-developed superficial root, inconspicuous deep root, shaft bent at midpoint, forming angle of approximately 60°, evenly short curved point; posterior anchor with inconspicuous roots, sclerotized cap of base with small protuberance for articulation to posterior bar; evenly curved shaft and short point; anterior bar broadly V-shaped, with small posteromedial projection; and posterior bar anteriorly expanded on it midportion, with expanded ends slightly curved in posterior direction.

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.

Monogenoidean parasites of freshwater stingrays (Rajiformes: Potamotrygonidae) from the Negro River, Amazon, Brazil: species of Potamotrygonocotyle (Monocotylidae) and Paraheteronchocotyle (Hexabothriidae).

Five new species of Potamotrygonocotyle (Monocotylidae) are described and Paraheteronchocotyle amazonense Mayes, Brooks et Thorson, 1981 (Hexabothriidae) is redescribed from monogenoideans collected on the gills of species of Potamotrygonidae from the Negro River, Amazon, Brazil. Potamotrygonocotyle quadracotyle sp. n. and P. umbella sp. n. were found parasitizing an undescribed species of Potamotrygon; Potamotrygonocotyle rarum sp. n. is described from Potamotrygon schroederi; Potamotrygonocotyle rionegrense inhabits Potamotrygon cf. motoro; Potamotrygonocotyle aramasae sp. n. is a parasite of Paratrygon aiereba; and Paraheteronchocotyle amazonense is reported from Potamotrygon orbignyi. The diagnosis of Paraheteronchocotyle is emended, and P. amazonense is redescribed.

The status of Acleotrema Johnston & Tiegs, 1922 and Heteroplectanum Rakotofiringa, Oliver & Lambert, 1987 (Monogenoidea: Diplectanidae), with the redescription of Acleotrema girellae Johnston & Tiegs, 1922.

Acleotrema Johnston & Tiegs, 1922 is resurrected and its diagnosis amended. A. girellae Johnston & Tiegs, 1922 is redescribed based on the lectotype from the Australian Museum (Sydney, Australia). A. kyphosi Yamaguti, 1968 is considered a junior synonym of A. girellae. Heteroplectanum Rakotofiringa, Oliver & Lambert, 1987 is considered a junior synonym of Acleotrema. The nine species of the latter genus are transferred to Acleotrema as: A. diplobulbus (Yamaguti, 1968) n. comb., A. nenue (Yamaguti, 1968) n. comb., A. spiculare (Yamaguti, 1968) n. comb., A. yamagutii (Oliver, 1983) n. comb., A. nenuoides (Rakotofiringa, Oliver & Lambert, 1987) n. comb., A. parastromatei (Rakotofiringa, Oliver & Lambert, 1987) n. comb., A. serrulopenis (Rakotofiringa, Oliver & Lambert, 1987) n. comb., A. tamatavense (Rakotofiringa, Oliver & Lambert, 1987) n. comb. and A. oliveri (León-Règagnon, Pérez-Ponce de León & Garcia- Prieto, 1997) n. comb. An historical account of the species of Acleotrema is presented.

Revision and phylogeny of rhamnocercinae monaco, Wood et Mizelle, 1954 (Monogenoidea: Diplectanidae).

Species of Rhamnocercinae Monaco, Wood et Mizelle, 1954 are gill parasites of sciaenid fishes (Perciformes). Seven are marine species (three in the western Atlantic and four in oriental Pacific) and one is a neotropical freshwater species (Rio Doce Basin, Brazil). While the status of the subfamily may be questioned, this assemblage of species is apparently supported by several shared apomorphic and plesiomorphic characters, such as: (1) peduncular spines with anterior and posterior roots; (2) haptor laterally expanded, armed with anchors (two pairs); bars (one ventral, two dorsal); 14 hooks and haptoral accessory spines; and (3) double (nested) tubes of the male copulatory organ (MCO), directed posteriorly with the genital pore lying posterior to the MCO. The phylogenetic hypothesis for the eight known species of this clade is: (Spinomatrix penteormos (Rhamnocercoides stichospinus, Rhamnocercoides menticirrhi) Rhamnocercus oliveri (Rhamnocercus rhamnocercus (Rhamnocercus stelliferi, Rhamnocercus bairdiella, Rhamnocercus margaritae)). This hypothesis indicates that Spinomatrix penteormos represents the sister group of all remaining rhamnocercines. The resulting phylogenetic sister-group relationships support the transfer of Rhamnocercus stichospinus Seamster et Wood, 1956 to Rhamnocercoides Luque et Iannacone, 1991 as Rhamnocercoides stichospinus (Seamster et Wood, 1956) n. comb.

Neotropical Monogenoidea. 43. Diplectanum monticellii n. sp. (Diplectanidae) from the gills of Cynoscion leiarchus (Perciformes: Sciaenidae) in Brazil.

Diplectanum monticellii n. sp. is described from the gills of Cynoscion leiarchus, a marine Sciaenidae, from Itacuruçá, Rio de Janeiro (type locality); Baía de Guaratuba, Paraná; and Pontal do Sul, Paraná in Brazil. The new species is characterized by the following features: bell-shaped male copulatory organ with a sleevelike base, accessory piece absent, vas deferens looping left intestinal cecum, vaginal aperture sinistroventral, and ventral anchor with elongate superficial and deep roots.

Neotropical Monogenoidea. 40. Protorhinoxenus prochilodi gen. n., sp. n. (Monogenoidea: Ancyrocephalinae), parasite of prochilodus lineatus (Characiformes: Prochilodontidae) from south Brazil.

The monotypic Protorhinoxenus gen. n. is proposed to accommodate a species with the following characteristics: 1) tubular sclerotised vagina, 2) vaginal pore dextrolateral, 3) ventral and dorsal anchors with undifferentiated elongate shaft and base (representing approximately 2/3 of the length of anchor), and 4) superficial and deep roots of ventral and dorsal anchors lacking. Protorhinoxenus prochilodi sp. n. is described from the gills of Prochilodus lineatus (Valenciennes) of the Represa Capivari-Cachoeira, Municipality of Campina Grande do Sul, metropolitan area of Curitiba, Paraná. Specimens of other probable new species of Protorhinoxenus are reported from Prochilodus lineatus of the Rio Paranapanema, Municipality of Salto Grande, São Paulo; Hoplias spp. of the Rio Dois de Fevereiro, Municipality of Antonina, Paraná, and the Rio Piraquara, metropolitan area of Curitiba, Parana; Leporinus elongatus Valenciennes of the Rio Tibagi, Municipality of Jataizinho, Parana; and Schizodon fasciatum Agassiz of the Rio Solimões, island of Marchantaria, near Manaus, Amazonas. Protorhinoxenus appears to be a sister group of Rhinoxenus Kritsky, Boeger et Thatcher, 1988 based on the following apparent synapomorphies: 1) ventral and dorsal anchors lacking superficial and deep roots, 2) ventral and dorsal anchors with elongate shaft, and 3) male copulatory organ with counterclockwise rings.

Neotropical Monogenoidea. 24. Rhinoxenus bulbovaginatus n. sp. (Dactylogyridae, Ancyrocephalinae) from the nasal cavity of Salminus maxillosus (Osteichthyes, Characidae) from the rio Paraná, Paraná, Brazil

Rhinoxenus bulbovaginatus n. sp. is described from the nose of Salminus maxillosus (Characidae) collected in the basin of the rio Paraná, near the city of Porto Rico, state of Paraná, Brazil. The new species can be differentiated from the other three species in the genus by the morphology of the copulatory complex, vagina, and ventral anchor. The sister group relationship of the known species of Rhinoxenus was determined using techniques of Phylogenetic Systematics (Cladism). The resulting cladogram (C.I.=100 por cento) indicates that the new species is most closely related to R. piranhus Kritsky, Boeger and Thatcher, 1988. The other two species of the genus, R. arietinus Kritsky, Boeger and Thatcher, 1988 and R. nyttus Kritsky, Boeger and Thatcher, 1988, both parasites of Anostomidae fishes, have a paraphyletic position in the cladogram, suggesting that the origin of at least one of them can not be associated to cospeciation.