Accessory Piece Research Articles

A new species of Aphanoblastella Kritsky, Mendoza-Franco and Scholz, 2000 (Monogenea, Dactylogyridae) parasitic on heptapterid catfish (Siluriformes) in the Neotropical region.

Aphanoblastella magna n. sp. is described from the gills of the heptapterid catfish Pimelodella avanhandavae Eigenmann, 1917 in southeastern Brazil (Paraná River Basin). This new species most closely resembles Aphanoblastella chagresii Mendoza-Franco, Aguirre-Macedo and Vidal-Martínez, 2007 described from a congeneric fish host in Panama, but can be distinguished by the shape of the accessory piece and shape and size of the ventral and dorsal bars. From the other species of the genus, A. magna n. sp. differs mainly in the shape of the male copulatory organ (MCO), which is sinuous, versus spirally coiled in other species of the genus, except for A. travassosi (Price, 1938), and by the accessory piece which resembles a 'shoehorn'. Aphanoblastella magna n. sp. is the seventh species of the genus and the first dactylogyrid described from P. avanhandavae. A partial 28S rDNA gene sequence of the new species is also provided; it forms a monophyletic clade with two congeners for which molecular data are available.

The first record of Ligophorus Euzet & Suriano, 1977 (Monogenea: Dactylogyridae) on Crenimugil buchanani (Teleostei: Muglidae) from Thailand based on morphological and molecular analyses.

Ligophorus satunensis n. sp. was collected from the bluetail mullet, Crenimugil buchanani (Bleeker, 1853), caught off Satun, Thailand, representing the first report of the Ligophorus species in Thailand. The new species is most similar to Ligophorus fenestrum Soo & Lim, 2012 in its fenestrated dorsal hamuli, a ventral bar with a long, bifurcated anteromedian protuberance (AMP) without lateral pieces, and a non-sclerotized vagina. However, it differs from the latter in its dorsal hamuli (up to two layers of fenestrations of the dorsal hamuli in L. satunensis n. sp. vs six layers in L. fenestrum), ventral hamuli (nonfenestrated vs fenestrated), penis (turning a full circle before reaching the genital pore vs turning less than half a circle), and its accessory piece (non-grooved basally and grooved distally vs simply grooved along its entire length). A single specimen, very similar to L. satunensis n. sp., obtained from the same host fish, which can be differentiated from the latter by a considerably shorter AMP of the ventral bar and a smaller and slender dorsal hamuli, is tentatively designated here as Ligophorus sp. Moreover, the phylogenetic trees constructed from the concatenated sequences of partial large-subunit nuclear ribosomal DNA (28S) and nuclear ribosomal internal transcribed spacer 1 (ITS1) regions support that L. satunensis n. sp. is a new species closely related to L. fenestrum.

Xenoligophoroides cobitis (Ergens, 1963) n. g., n. comb. (Monogenea: Ancyrocephalidae), a parasite of Gobius cobitis Pallas (Perciformes: Gobiidae) from the Mediterranean and Black seas.

Based on an integrative taxonomic approach, combining morphological characters and partial sequences of the nuclear 28S rRNA gene, a new genus and combination for the species Xenoligophoroides cobitis (Ergens, 1963) is proposed, to accommodate ancyrocephalid monogeneans, parasites on the gills of Gobius cobitis Pallas (Gobiidae) from the western Mediterranean Sea and the northern Black Sea. A morphological comparison of newly collected material with the descriptions of Ancyrocephalus cobitis Ergens, 1963 and Haliotrema cupensis Sasal, Pages & Euzet, 1998, recently synonymised and named as Haliotrema cobitis (Ergens, 1963), confirms their similarity and belonging to the same species. However, characters of this species, as the vas deferens not looping the caecal branch, the bilobed base of the male copulatory organ and the marginal hooks with an upright thumb, do not correspond to the diagnosis of Haliotrema Johnston & Tiegs, 1922. Morphologically, this species is close to members of Ligophorus Euzet & Suriano, 1977 and Kriboetrema Sarabeev, Rubtsova, Yang & Balbuena, 2013, but differs from the former in the accessory piece articulated with MCO and two prostatic reservoirs, and from the latter in the uncoiled MCO with bilobed base and the dextral vaginal pore. Moreover, all species of Ligophorus and Kriboetrema are parasites of grey mullets. A 28S rDNA-based phylogenetic analysis of sequences derived from specimens of X. cobitis from the Mediterranean and Black seas, along with sequences from several closely related genera of the Ancyrocephalidae, suggested the occurrence of a new taxonomic unit, which corresponded to the X. cobitis specimens. This finding supports the establishment of the new genus for the ancyrocephalid parasites on the gills of G. cobitis from the western Mediterranean Sea and the northern Black Sea.

Dactylogyrids (Platyhelminthes: Monogenoidea) from the gills of Hassar gabiru and Hassar orestis (Siluriformes: Doradidae) from the Xingu Basin, Brazil

Four species ofCosmetocleithrum(three new) and one new species ofVancleaveusare described or reported parasitizing the gills of doradid catfishes (Siluriformes) from Xingu River and related tributaries:Cosmetocleithrumphryctophallussp. nov. andCosmetocleithrumbifurcumMendoza-Franco, Mendoza-Palmero & Scholz, 2016 fromHassarorestis;Cosmetocleithrumleandroisp. nov. fromHassargabiru;Cosmetocleithrumakuandubasp. nov. andVancleaveusklassenisp. nov. fromHassarorestisandH.gabiru.Cosmetocleithrumphryctophallussp. nov. differs from its congeners by possessing a male copulatory organ (MCO) with 2 ½ counterclockwise rings, and an accessory piece with an elongate torch-shaped blade.Cosmetocleithrumleandroisp. nov. has a MCO comprising a coil of about 3 ½ rings, a sigmoid accessory piece with a cup-shaped distal portion, a single type of hooks, and anchors with poorly differentiated roots.Cosmetocleithrumakuandubasp. nov. is characterized mainly by having a J-shaped MCO, an elongate accessory piece with sharp distal region, distal portion with a small gutter, and a heavily sclerotized vagina with short “S”-shaped vaginal canal.Vancleaveusklassenisp. nov. differs from the other species of the genus occurring in doradids by possessing anchors with triangular to subtriangular superficial root, developed deep root, and a coiled MCO with 2 ½ counterclockwise rings.Cosmetocleithrumbifurcumwas reported for the first time parasitizing doradids from Brazilian Amazon.

A new species of Cacatuocotyle (Monogenea, Dactylogyridae) parasitizing Astyanax spp. (Characiformes, Characidae) from Brazil, including molecular data and a key to species identification.

The present study describes Cacatuocotyle papilionis n. sp. (Monogenea, Dactylogyridae) from the skin of the characid fishes Astyanax lacustris (Lütken, 1875) (=Astyanax altiparanae Garutti & Britski, 2000) and Astyanax fasciatus (Cuvier, 1819) (Characiformes, Characidae) from the Southeast of Brazil, supported by morphological and molecular data. The new species differs from all congeners, mainly due to the morphology of the ventral bar (resembling a butterfly), accessory piece, and the number of rings of the male copulatory organ (MCO), comprising a coiled tube with 4.5-5.5 counterclockwise rings. The first molecular data for this monogenean genus is provided in this study, using the partial sequences of the ribosomal gene (28S), as well as providing an identification key to the species.

Monogenoidean parasites of Acestrorhynchus falcatus (Characiformes: Acestrorhynchidae) from Pará, Brazil: species of Diaphorocleidus and Rhinoxenoides n. gen. (Monogenoidea: Dactylogyridae).

Two new species of Diaphorocleidus and one new species of Rhinoxenoides n. gen. are described from the gills of Acestrorhynchus falcatus (Bloch) from rivers of north-eastern Pará, Brazil. Diaphorocleidus jaymedeloyolai n. sp. is characterized by a male copulatory organ (MCO) possessing three counterclockwise coils; similar anchors with subtriangular superficial roots; a ventral bar with posteromedial projection; and hooks of pairs 1, 4 and 7 approximately three times longer than hook pair 5. Diaphorocleidus sclerocolpus n. sp. differs from its congeners by a dual-branched accessory piece articulated with the MCO and a sclerotized tubular vagina with a bottle-shaped vestibule. Rhinoxenoides n. gen. is proposed and is characterized by possessing: MCO sclerotized with clockwise coils; an accessory piece articulated to the base of MCO; a sinistroventral vaginal aperture; ventral anchor with conspicuous roots; dorsal anchor with superficial root five times longer than deep root; and absence of dorsal bar. The proposal of Rhinoxenoides n. gen. is also supported by its phylogenetic relationship with Protorhinoxenus prochilodi and species of Rhinoxenus, using 16 morphological characters, which resulted in the following hypothesis of sister-group relationships: Rhinoxenoides n. gen. [Protorhinoxenus (Rhinoxenus curimatae (R. nyttus (R. bulbovaginatus (R. guianensis, R. piranhus, R. euryxenus (R. arietinus, R. anaclaudiae)))))].

Ligictaluridus michaelalicea n. sp. (Monogenea: Dactylogyridae) from flathead catfish (Pylodictis olivaris) in the upper Mississippi River, including remarks on taxonomy influencing monogenean treatment regulation in the United States.

Ligictaluridus michaelalicea n. sp. (Monogenea: Dactylogyridae, Ancyrocephalinae) is described from the gills of Pylodictis olivaris (Siluriformes: Ictaluridae) from Wisconsin and Iowa portions of the upper Mississippi River. Diagnostic features include a relatively large, strongly curved tubular cirrus with minor terminal flare; an accessory piece with a prominent basal lobe and a simple, thick terminal limb featuring a thin lateral flange and blunt distal tip devoid of recurved hooks. The sinistral vagina, two prostatic reservoirs, and a terminal seminal vesicle of the vas deferens are prominent. The anchors, ventral and dorsal bars, and hooks are similar in overall form to those of other members of the genus. The description includes sequence data for the 18S rRNA gene, which aligned most closely with species of ancyrocephaline monogeneans, with the highest similarity being with Ligictaluridus pricei (Mueller, 1936). Other monogenean species identified from the flathead catfish examined included L. pricei and Ligictaluridus mirabilis (Mueller, 1937). L. michaelalicea n. sp. is the fourth species to be described from P. olivaris within its natural range in central and eastern North America. Implications resulting from taxonomic name changes, including species of Ligictaluridus, and United States Food and Drug Administration treatment regulations are discussed. An updated key to species of the genus Ligictaluridus is presented.

Six new dactylogyrid species (Platyhelminthes, Monogenea) from the gills of cichlids (Teleostei, Cichliformes) from the Lower Congo Basin.

The Lower Congo Basin is characterized by a mangrove-lined estuary at its mouth and, further upstream, by many hydrogeographical barriers such as rapids and narrow gorges. Five localities in the mangroves and four from (upstream) left bank tributaries or pools were sampled. On the gills of Coptodon tholloni, Coptodon rendalli, Hemichromis elongatus, Hemichromis stellifer and Tylochromis praecox, 17 species of parasites (Dactylogyridae & Gyrodactylidae, Monogenea) were found, eight of which are new to science. Six of these are herein described: Cichlidogyrus bixlerzavalai n. sp. and Cichlidogyrus omari n. sp. from T. praecox, Cichlidogyrus calycinus n. sp. and Cichlidogyrus polyenso n. sp. from H. elongatus, Cichlidogyrus kmentovae n. sp. from H. stellifer and Onchobdella ximenae n. sp. from both species of Hemichromis. On Cichlidogyrus reversati a ridge on the accessory piece was discovered that connects to the basal bulb of the penis. We report a putative spillback effect of the native parasites Cichlidogyrus berradae, Cichlidogyrus cubitus and Cichlidogyrus flexicolpos from C. tholloni to the introduced C. rendalli. From our results, we note that the parasite fauna of Lower Congo has a higher affinity with the fauna of West African and nearby freshwater ecoregions than it has with fauna of other regions of the Congo Basin and Central Africa.

New species of Paracolpenteron n. gen. and Ancyrocephalus (Monogenea, Dactylogyridae) inhabiting the urinary bladder and gills of the Maya needlefish Strongylura hubbsi (Beloniformes, Belonidae) from Chiapas, Mexico.

Parasitological examination of the maya needlefish Strongylura hubbsi Collette (Belonidae) from the Rio Lacantún basin in the Montes Azules Biosphere Reserve, Chiapas, Mexico showed that specimens were parasitized by two monogenean species in two different sites: Paracolpenteron hubbsii n. gen., n. sp in the urinary bladder and Ancyrocephalus chiapanensis n. sp in the gill lamellae. Paracolpenteron hubbsii differs from other dactylogyrid species without a haptoral anchor/bar complex infecting the urinary systems, gills and nasal cavities by the general morphology of hooks, a dextral vaginal opening, a tubular male copulatory organ comprising a base from which a coiled shaft arises in counterclockwise direction, and an unarticulated Y-shaped accessory piece. Ancyrocephalus chiapanensis n. sp. resembles Ancyrocephalus cornutus William & Rogers, 1972 from the gills of Strongylura marina from Florida from which it differs in possessing a twisted tube of the male copulatory organ (curved in A. cornutus), ventral bar with cavities on the ends (cavities absent in A. cornutus) and by the size of the ventral (length 31–34 μm vs. 24–27 μm in A. cornutus) and dorsal (length 25–28 μm vs. 18–22 μm in A. cornutus) anchors. These new monogeneans are described herein and their biogeography is briefly discussed based on the previous phylogenetic hypotheses concerning the host family.

A new genus and two new species of dactylogyrid monogeneans from gills of Neotropical catfishes (Siluriformes: Doradidae and Loricariidae)

A new genus of dactylogyrid monogeneans (Ancyrocephalinae), Paracosmetocleithrum n. gen., is erected to accommodate P. trachydorasi n. sp. from Trachydoras paraguayensis (Siluriformes: Doradidae) in the Upper Paraná River basin, Brazil. The new genus differs from Neotropical dactylogyrids in the presence of a well-developed ornamentation in the middle portion of the ventral bar, and a sclerotized patch on the surface of the dorsal bar with an inconspicuous medial process that possesses two submedial projections arising from the tapered ends of this patch. In addition, Demidospermus rhinelepisi n. sp. is described from Rhinelepis aspera (Siluriformes: Loricariidae). The new species, which is the fifth species of the genus described from loricariids, can be differentiated from congeners by the possession of a sclerotized patch attached to the middle portion of the ventral bar, and by morphology of the accessory piece, which presents broad ends, tapering in the centre, rounded proximal end, distal end folding on both sides with folds extending to approximately ¾ of the accessory piece length. Molecular data on both new species are also provided and species composition of Demidospermus, recently revealed as polyphyletic by molecular studies including the present one, is discussed.

An unusual new species of Oenonidae (Polychaeta, Eunicida) from the North Atlantic Ocean

A new species of Tainokia (family Oenonidae) is described from the Gulf of Cadiz (NE Atlantic). Tainokia logachevae sp. nov. was retrieved from a dredge sample across the crater of Mercator mud volcano at 375–397 m depths. It is characterized by having H-shaped mandibulae with distal bidentate accessory pieces, maxillae I and II dentate along the entire margin and greatly asymmetric, with 6 or 10 teeth, and maxillae III, IV, and V with 5/6, 4/5, and 1 teeth, respectively. DNA fragments from the mitochondrial genes COI and 16S rDNA, and the nuclear genes 18S rDNA and 28S rDNA are given, providing a molecular tag for future reference of this species. This is the first report of the genus for both the deep sea and for the Atlantic Ocean.

Dactylogyrids (Monogenea) parasitic on marine fish from Peru including the description of a new species of Haliotrema Johnston & Tiegs, 1922 and two new species of Parancylodiscoides Caballero & C. & Bravo-Hollis, 1961

A parasitological survey searching dactylogyrids (Monogenea) infesting the gills of Peruvian marine fish was carried out during the 2015–2016 period. The gills of three teleosts species, 12 Hemanthias peruanus (Steindachner), 16 Hemanthias signifer (Garman) (Serranidae) and 4 Scarus perrico Jordan & Gilbert (Scaridae), were sampled. A new species of Haliotrema and two new species of Parancylodiscoides were described: Haliotrema sanchezae n. sp. from S. perrico, Parancylodiscoides peruensis n. sp. from H. peruanus and P. signiferi n. sp. from H. signifer. Haliotrema sanchezae n. sp. differs from other congeneric species by its male copulatory organ (tapered-shaped cirrus tube, with cylinder-shaped base and a membranous, blanket-shaped accessory piece), and the morphology of its transverse bars (X-shaped ventral bar and mask-shaped dorsal bar). Parancylodiscoides peruensis n. sp. differs from all other members of Parancylodiscoides by having a tapered-shaped copulatory organ with curved distal tip and a bell-shaped base having two lateral knobs and short arm. Parancylodiscoides signiferi n. sp. can be differentiated from its congeners by its male copulatory organ, which has tubular-shaped with a loop at distal end and a slightly expanded base having a short and broad arm. Present findings are added to the other 3 marine dactylogyrid previously reported from Peru.

Two new species of Annulotrema (Monogenea: Dactylogyridae) from Hydrocynus vittatus (Characiformes: Alestidae) in Lake Kariba, Zimbabwe.

Two new and one known species of Annulotrema Paperna & Thurston, 1969 are reported from the gills of the tigerfish Hydrocynus vittatus Castelnau, 1861, collected in Lake Kariba, Zimbabwe. The new species, Annulotrema pseudonili n. sp. and A. bracteatum n. sp., are described and distinguished mainly on the basis of features of the male copulatory organ (MCO). Annulotrema pseudonili n. sp. most closely resembles A. nili Paperna, 1973, but differs from it by possessing a more delicate MCO with a thin-walled base without a fibrous distal part. Annulotrema bracteatum n. sp. is most similar to Annulotrema ruahae Paperna, 1973, from which it differs by having an MCO composed of a longer copulatory tube and a leaf-shaped accessory piece enveloping the distal part of the tube. The presence of Annulotrema pikoides Guégan, Lambert & Birgi, 1988 on H. vittatus in Zimbabwe represents a new locality record for this parasite.

Species of Tetrancistrum Goto & Kikuchi, 1917 (Monogenea: Dactylogyridae) from the gills of the whitespotted rabbitfish, Siganus canaliculatus (Park) (Perciformes: Siganidae) off Omani coasts, with a description of Tetrancistrum labyrinthus n. sp.

Tetrancistrum labyrinthus n. sp. is described from the gills of the marine herbivorous fish Siganus canaliculatus (Park) found in the Western Indian Ocean (Sea of Oman and Arabian Sea). Comparative morphological analyses of all previously described species of Tetrancistrum Goto & Kikuchi, 1917 confirmed the distinct status of T. labyrinthus n. sp. The new species closely resembles T. suezicum Paperna, 1972 and T. oraminii Young, 1967 in the morphology of the male copulatory organ. However, it can be distinguished by possessing a thin handle-like anterior basal flange and a compound accessory piece that is composed of a tapering rod-shaped anterior part and a large cylindrical, elongated posterior part. The new species can be further distinguished from other Tetrancistrum species by its highly sclerotised and complex disc-shaped vaginal vestibule. This is the first record of Tetrancistrum from the Sea of Oman and Arabian Sea, and the fourth of nominal species of Tetrancistrum known to parasitise Siganus canaliculatus (Park). In addition, T. indicum Paperna, 1972 is re-described here with an updated locality record.

A New Species of Cosmetocleithrum (Monogenea, Dactylogyridae), a Gill Parasite of Trachelyopterus galeatus (Siluriformes, Auchenipteridae) from Brazil, with Notes on the Morphology of Cosmetocleithrum striatuli

ABSTRACT: The present study describes a new species of Cosmetocleithrum Kritsky, Thatcher and Boeger, 1986 from the gills of the catfish Trachelyopterus galeatus (Linnaeus, 1766) from the mouth of the Aguapei River, municipality of Castilho, Sao Paulo State, Brazil. Cosmetocleithrum laciniatum n. sp. closely resembles Cosmetocleithrum striatuli Abdallah, Azevedo and Luque, 2012 and Cosmetocleithrum longivaginatum Suriano and Incorvaia, 1995 by the shape of dorsal and ventral bars (straight with enlarged ends), and Cosmetocleithrum gussevi Kritsky, Thatcher and Boeger, 1986 by having a Y-shaped accessory piece. The new species can be distinguished from most of its congeners by having a coiled cirrus with a 1½ counterclockwise ring with a sclerotized base possessing lateral flaps. This species is the second found to contain members of Cosmetocleithrum parasitizing the gills of Auchenipteridae. A note on the morphology of C. striatuli, a parasite of Trachelyopterus striatulus, is also presented.

A new species of Tereancistrum (Monogenea, Dactylogyridae) from the gills of three Leporinus species (Characiformes, Anostomidae) and a revised description of Tereancistrum parvus

The present study describes Tereancistrum flabellum n. sp. (Dactylogyridae, Ancyrocephalinae) from the gills of the anostomid fishes Leporinus friderici, Leporinus amblyrhynchus and Leporinus elongatus from two freshwater ecosystems in the south east of Brazil. This new species is mainly characterized by the morphology of the copulatory complex (such as the MCO base formed by two fan-shaped structures, and accessory piece flattened, curved, rigid and channeled), a dorsal anchor with a well-developed superficial and inconspicuous deep root, and the shape of the accessory anchor sclerite with small spathulate termination. Tereancistrum flabellum n. sp. is the first record of a dactylogyrid from L. amblyrhynchus. The description of Tereancistrum parvus is also emended to correct and complement previous descriptions and the species is reported for the first time in Schizodon nasutus.

Four new species of Dactylogyrus Diesing, 1850 (Monogenea: Dactylogyridae) parasitising the gills of northern Moroccan Luciobarbus Heckel (Cyprinidae): morphological and molecular characterisation.

Four new species of Dactylogyrus Diesing, 1850 are described from the gills of three species of Luciobarbus Heckel collected from various hydrographical basins in northern Morocco: Dactylogyrus scorpius n. sp. from Luciobarbus rifensis Doadrio, Casal-Lopez & Yahyaoui; D. benhoussai n. sp. from L. moulouyensis Pellegrin; and D. varius n. sp. and D. falsiphallus n. sp. from L. maghrebensis Doadrio, Perea & Yahyaoui. The descriptions of the new species are confirmed by molecular data (partial 18S rDNA, ITS1, and partial 28S rDNA sequences). All four species belong to the group of Dactylogyrus species, possessing a cross-shaped ventral bar and a male copulatory organ composed of a loosely coiled copulatory tube and an accessory piece with a capsule-like base and recurved distal portion. Given the high shape variability of the haptoral anchors reported among specimens of D. varius n. sp., three morphological forms within this species (D. varius f. vulgaris, D. varius f. magnus, and D. varius f. dromedarius) are recognised. However, specimens belonging to D. benhoussai n. sp. and D. varius f. vulgaris were morphologically very similar and were discriminated with certainty, only when using molecular data.

Redescription of Cichlidogyrus philander (Monogenea, Ancyrocephalidae) using scanning electron microscopy (SEM) and molecular analysis.

The sclerotized structures of monogeneans have traditionally been studied by light microscopy and different staining techniques. Recently, enzymatic digestion followed by scanning electron microscopy (SEM) has enabled the examination of structural details not visible with light microscopy. In order to obtain better, and more accurate, morphological information on sclerotized structures not affected by mounting medium or cover slip pressure, the sclerites of Cichlidogyrus philander Douëllou, 1993 (Monogenea, Ancyrocephalidae), collected from Pseudocrenilabrus philander (Weber, 1897), were redescribed using SEM. Parasites were collected from Padda Dam, Gauteng, South Africa and soft tissue was digested to release the sclerotized structures. The digested tissue also provided sufficient genetic material for molecular characterization of this species. Cichlidogyrus philander is characterised by a penis with a sharp, curved, lateral termination, an accessory piece with a hook-like extremity that may appear forked terminally, and lack of a visible vagina. The transverse bars have concave and convex surfaces with ribs on the concave surface. The dorsal bar bears fenestrations at the base of the auricles and the ventral and dorsal gripi are dissimilar. Furthermore, the large first pair of uncinuli shows lateral wings on the left side of the base. On top of this wing, a ball-like structure with a small fenestration is visible. Genetic characters derived from the 28S rDNA, the COI mitochondrial DNA and ITS1 rDNA regions distinguish C. philander from all other Cichlidogyrus sequenced species.

<i>Dactylogyrus oryziasi</i> n. sp. (Monogenea: Dactylogyridae) from <i>Oryzias latipes</i> (Beloniformes: Adrianichthyidae) in Japan

Dactylogyrus oryziasi n. sp. (Monogenea: Dactylogyridae) is described from the gills of the southern medaka Oryzias latipes (Temminck and Schlegel, 1846) (Beloniformes: Adrianichthyidae) collected from an irrigation canal, Tokushima city, Tokushima Prefecture, Shikoku, Japan. This new species resembles Dactylogyrus rysavyi Ergens, 1970 in having a coiled penis passing through a tube of an accessory piece associated with a sigmoid rod, and shapes of haptoral parts, but these species differ from each other by turns of the penis and a connection point between the rod and tube of the accessory piece. This is the first record of Dactylogyrus from beloniform fish.

Dactylogyrid monogeneans parasitising Cyphocharax voga (Hensel) (Teleostei: Curimatidae) from the Pampas region, Argentina: new and previously described species.

Most studies on dactylogyrid monogeneans in Argentina have been carried out during 1980s and 1990s. Many of these species have been later synonymised and other remain under a confusing taxonomic status, particularly those parasitising Cyphocharax voga (Hensel) (Teleostei: Curimatidae). In order to clarify the identity of dactylogyrids, new material was collected from fishes in Lake Chascomús, Buenos Aires Province, Argentina. A total of four species was found in the gills of C. voga. Two known species, Curvianchoratus singularis (Suriano, 1980) Suriano, 1986 and Palombitrema triangulum (Suriano, 1981) Suriano, 1997, are redescribed and their generic and specific status discussed, and two new species are described. Urocleidoides surianoae n. sp. can be distinguished from its congeners by having an anterior medial projection in the ventral bar and a laminar ligament connecting the base of the male copulatory organ and accessory piece. Annulotrematoides bonaerensis n. sp. differs from its congeners principally by having a ventral bar with an anterior medial projection. The diversity of dactylogyrids harboured by C. voga indicates the need of further studies in the Pampas region, which will provide interesting and valuable sources of evidence for future zoogeographical and evolutionary research on dactylogyrids in the Neotropics.