Two new species of Cryptocephalum n. gen. (Monogenoidea: Dactylogyridae) from the cephalic lateral line of Percichthys trucha (Perciformes: Percichthyidae) in Patagonia, Argentina

Two new species of Monogenoidea were found parasitizing the cephalic lateral line canals of Percichthys trucha (Valenciennes) (Perciformes: Percichthyidae). These species are described as members of a newly proposed genus of Dactylogyridae. Cryptocephalum n. gen. is characterized by the site of infection and the combination of the several features: ventral and dorsal anchor/bar complexes, anchors with strongly elongated shaft and recurved point, shaft and point of dorsal anchors protruding laterally from haptor, hooks with 2 subunits and with pair 5 smaller than the others; gonads overlapping; coiled male copulatory organ with counterclockwise rings, accessory piece formed by 2 distinct parts, and a tubular, sclerotized ventral vagina. C ryptocephalum petreum n. sp. is characterized by having both anchor pairs protruding laterally from haptor, male copulatory organ with a coil of 2-1/2 rings, accessory piece tweezers-shaped, and sclerotized vaginal vestibule. Cryptocephalum spiralis n. sp. has ventral anchors protruding ventrally and dorsal ones protruding laterally, male copulatory organ with a coil of 1-1/2 rings, the antero-dorsal part of the accessory piece saddle-shaped, vaginal vestibule not present, and coiled vagina. This is the first record of Dactylogyridae species parasitizing the cephalic lateral line of fishes.     

Six new species of Rhamnocercus Monaco,Wood & Mizelle, 1954 (Monogenea: Diplectanidae) infecting the gills from South American sciaenid fishes

A parasitological survey searching diplectanids (Monogenea: Diplecatnidae) infesting the gills of marine fishes from South America was carried out during the 2019–2020 period. The gills of four sciaenid species, 2 Cheilotrema fasciatum Tschudi, 1 smalleye croaker Nebris microps Cuvier, 2 royal highhat Pareques lanfeari (Barton), and 1 minor stardrum Stellifer minor (Tschudi), were sampled. Six new species of Rhamnocercus Monaco, Wood & Mizelle, 1954 were described: Rhamnocercus chacllae n. sp. and Rhamnocercus chaskae n. sp. from P. lanfeari, Rhamnocercus fasciatus n. sp. from C. fasciatum, Rhamnocercus microps n. sp. from N. microps, and Rhamnocercus rimaci n. sp. and Rhamnocercus tantaleani n. sp. from S. minor. Rhamnocercus chacllae n. sp. can be differentiated from its congeners by its L-shaped male copulatory organ (MCO) and by having an anteromedial slight notch at ventral bar. Rhamnocercus chaskae n. sp. differs from the other species of the genus by its long and straight MCO with bifid distal end and by having haptoral accessory spines at level of ventral bar with quadrifid distal portion. Rhamnocercus fasciatus n. sp. is characterized by possessing a straight and long MCO with truncated distal end, haptoral accessory spines at level of ventral bar with bifid distal portion, dorsal bars with a knob at lateral extremity, and a large vagina with bell-shaped. Rhamnocercus microps n. sp. differs from all congeners mainly by having a short and straight MCO with the distal end of internal tube spatulate and uncovered by external tube. Rhamnocercus rimaci n. sp. is can be distinguished from all other species of Rhamnocercus by having an almost J-shaped MCO with the distal end of external tube slight expanded and the distal end of internal tube narrow and uncovered by external tube. Rhamnocercus tantaleani n. sp. is mainly characterized by its MCO, which is tubular and straight, having the distal end of external tube bifurcated (right branch well-expanded and left branch narrow) and the distal end of internal tube enveloped by left branch of the external tube. This is the first data on the parasites of P. lanfeari, a little known, but popular fish in local markets from Peru. Rhamnocercus microps n. sp. is the first described species of Rhamnocercus in Brazil. The present finding brings to 12, the number of known species of Rhamnocercus. A key to Rhamnocercus species is provided.

     

Two new species of Haliotrema (Monogenoidea: Dactylogyridae) from Cirrhitus rivulatus (Perciformes: Cirrhitidae) from the Pacific coast of Mexico

During surveys of helminth parasites of marine fishes from the Pacific coast of the Guerrero State in Mexico, 2 undescribed species of Haliotrema Johnston and Tiegs, 1922 (sensu Young, 1968) (Dactylogyridae) were found infecting the gills of the giant hawkfish Cirrhitus rivulatus Valenciennes, 1846 (Perciformes, Cirrhitidae), i.e., Haliotrema cirrhitusi n. sp. and Haliotrema pollexinus n. sp. The new species are similar with respect to the morphology of the anchors with base-shaft junction crazed, hinged, or both; dorsal anchors with an elongate superficial root; a tubular male copulatory organ (MCO) with a cylinder-shaped base diagonally opening; and a membranous accessory piece, shaped like a vane, encircling MCO to form 2 complete spirals from the anterior margin of base to the terminal portion of the MCO. While H. cirrhitusi and H. pollexinus differ from all other species of the genus in the general morphology of the copulatory complex, only H. pollexinus notably differs from all these species in having a superficial, blade-like projection from the inner surface on the distal shaft of anchors. Haliotrema cirrhitusi and H. pollexinus are the only members of the genus recorded in the Mexican Pacific and from a cirrhitid host.     

Three new species of Protogyrodactylus Johnston & Tiegs, 1922 (Monogenoidea: Dactylogyridae) from the gills of the longtail silverbiddy Gerres longirostris (Teleostei: Gerreidae) in the Red Sea

Twenty-one specimens of the longtailed silverbiddy Gerres longirostris (Gerreidae) were examined for dactylogyrid parasites from the Nabq Managed Resource Protected Area, Ras Mohammed National Park (Red Sea) near Sharm El-Sheikh, South Sinai, Egypt. The diagnosis of Protogyrodactylus Johnston & Tiegs, 1922 was amended, and three new species, P. federicae n. sp., P. zullinii n. sp. and P. alatus n. sp., were recovered and described; the prevalence of each species was 100%. P. federicae most closely resembled P. alienus Bychowsky & Nagibina, 1974, but differed from it by possessing two anteromedial projections on the ventral bar, a claw-like ventral anchor sclerite and spatulate dorsal bars. P. zullini was most similar to P. quadratus Johnston & Tiegs, 1922, from which it differed by having a distal hook on the superficial root of the dorsal anchor, an evenly curved ventral anchor shaft and point, and a flange on the bulbous base of the male copulatory organ. P. alatus was closest to P. youngi Bychowsky & Nagibina, 1974, from which it differed by having delicate anchors and two prominent anteromedial processes on the ventral bar.     

Monogeneans of the catfish Pimelodus blochii Valenciennes (Siluriformes: Pimelodidae) from the Brazilian Amazon,with a description of a new species of Ameloblastella Kritsky,Mendoza-Franco & Scholz, 2000 (Monogenea: Dactylogyridae)

Ameloblastella amazonica n. sp. (Monogenea: Dactylogyridae) collected on the gills of Pimelodus blochii Valenciennes (Siluriformes: Pimelodidae) from Rivers Acre and Iaco, State of Acre (Brazil) is described. The new species differs from the congeners mainly by the morphology of the dorsal bar, i.e. slightly U-shaped bearing a posteriorly directed flap, arising from the anterior edge of its middle third. The most morphologically similar congeners, A. paranaensis (França, Isaac, Pavanelli & Takemoto, 2003) and A. satoi Monteiro, Kritsky & Brasil-Sato, 2010, resemble A. amazonica n. sp. regarding the general structure of the copulatory complex; however, besides other features, they also differ from the new species because their hooks are similar in size (vs hooks with three different sizes). In addition to the dorsal bar lacking a flap, A. amazonica n. sp. can be differentiated from all congeners based on the combination of the following features: size of hooks (one or two different sizes), shape of the dorsal bar (other than slightly U-shaped), anchor points largely passing the level of superficial root (vs not or slightly passing it), number of MCO rings (other than 3–4) and structure of the articulation between the MCO base and the accessory piece (other than thick, medium-sized, smooth and tubular). Demidospermus leptosynophallus Kritsky & Gutierrez, 1998 and Scleroductus yuncensi Jara & Cone, 1989 were also found infesting P. blochii, both representing new host and locality records.

     

<Emphasis Type="Italic">Spicocleidus namae</Emphasis> n. g., n. sp. (Monogenea: Dactylogyridae) on <Emphasis Type="Italic">Chanda nama</Emphasis> (Hamilton) from Lucknow,India

Spicocleidus n. g. is proposed for S. namae n. sp., a new monogenean collected from the gills of an ambassid, Chanda nama (Ham.), in the River Sai near Lucknow, Uttar Pradesh, India. The new genus is characterised by a pair of modified dorsal anchors (spikes), the absence of a dorsal bar, alate lateral expansion of the anterior haptor and the post-ovarian position of the testis.     

Three new species of Dactylogyrus Diesing, 1850 (Monogenea: Dactylogyridae) from the gills of the bala sharkminnow Balantiocheilos melanopterus (Cyprinidae) from Thailand

Three new species of Dactylogyrus are described from the gills of the cyprinid fish Balantiocheilos melanopterus (Bleeker) imported from Thailand via the aquarium trade. They are D. coartatus n. sp., D. macrocolpius n. sp. and D. melanopteri n. sp. The double-bar species, D. coartatus n. sp. and D. melanopteri n. sp., are characterised by hooks that are markedly large in relation to the size of the anchors. Clip-like anchors with a sharply recurved, long point are a unique feature of D. coartatus n. sp. The single-bar species, D. macrocolpius n. sp., is characterised by having a copulatory organ composed of a spiral copulum and a medial accessory piece with thorns.     

Neotropical Monogenoidea. 46. Three new species from the gills of introduced aquarium fishes in India,the proposal of Heterotylus n. g. and Diaphorocleidus n. g., and the reassignment of some previously described species of Urocleidoides Mizelle & Price, 1964 (Polyonchoinea: Dactylogyridae)

Three new species of the Dactylogyridae are described from aquarium fishes collected in India and two new genera are proposed: Heterotylus heterotylus n. g., n. sp. from Hypostomus sp. (Loricariidae), Diaphorocleidus armillatus n. g., n. sp. from Gymnocorymbus ternetzi (Characidae) and Urocleidoides vaginoclaustrum n. sp. from Xiphophorus helleri (Poeciliidae). Heterotylus n. g. is characterised by species having overlapping gonads (testis posterodorsal to the ovary), a mid-ventral vaginal aperture, a copulatory complex consisting of a relatively straight copulatory organ unarticulated to a complex accessory piece, erect acute hook thumbs, unexpanded hook shanks, dorsal and ventral anchor/bar complexes and absence of well-defined basal roots of the ventral anchors. Diaphorocleidus n. g. includes species with overlapping gonads (testis posterodorsal to the ovary), submarginal sinistral vaginal pore, a copulatory complex comprising a coiled (counterclockwise) copulatory organ unarticulated to an accessory piece, protruding depressed hook thumb, hook shank with two subunits (proximal subunit expanded), dorsal and ventral anchor/bar complexes and V-shaped bars. The following new combinations are proposed: D. affinis (Mizelle, Kritsky & Crane, 1968) n. comb. (syn. U. affinis Mizelle, Kritsky & Crane, 1968), D. kabatai (Molnar, Hanek & Fernando, 1974) n. comb. (syn. U. kabatai Molnar, Hanek & Fernando, 1974) and D. microstomus (Mizelle, Kritsky & Crane, 1968) n. comb. (syn. U. microstomus Mizelle, Kritsky & Crane, 1968).     

Four new species of dactylogyrids (Monogenea: Dactylogyridae) parasitic on gills of labrid and sparid fishes from Southeastern Pacific Ocean off Peru

During a research on gill ectoparasites of Peruvian marine fishes, four dactylogyrid (Monogenea) species, parasitising two teleost species, Bodianus diplotaenia (Gill) (Labridae) and Calamus brachysomus (Lockington) (Sparidae), were found. Euryhaliotrema luisae n. sp. ex C. brachysomus is differentiated from other congeneric species by the morphology of the male copulatory organ, which comprises a coil of nine counterclockwise rings, and by the morphology of the anchors and bars. Euryhaliotrema magnopharyngis n. sp. ex C. brachysomus can be distinguished from all other congeners by having a well-developed pharynx occupying much of the anterior region and by the ventral bar, which is V-shaped, with well-elongated, thin arms. In addition, E. luisae n. sp. and E. magnopharyngis n. sp. can be differentiated from all other members of Euryhaliotrema Kritsky & Boeger, 2002 by the presence of a glandular oval plate lying on peduncle. Haliotrema diplotaenia n. sp. ex B. diplotaenia is characterised by the structure of the male copulatory organ, comprising a tapered-shaped cirrus tube with twisted acute tip and a filament-shaped accessory piece with medial and distal expansions, and by the morphology of the ventral bar (inverted W-shaped, with short lateral ends and two anterior conical protuberances). Haliotrema saezae n. sp. ex B. diplotaenia differs from all other members of Haliotrema Johnston & Tiegs, 1922 by having a tubular copulatory organ with curved distal tip and a filament-shaped accessory piece without lateral expansions, and by the morphology of anchors and bars. The present findings are added to the other six marine dactylogyrids previously reported from Peru.     

Five new monogenean species from the gills of Mulloidichthys vanicolensis (Perciformes: Mullidae) off New Caledonia, with the proposal of Volsellituba n. g. and Pennulituba n. g. (Monogenea: Dactylogyridae)

Three species of Volsellituba n. g. and two species of Pennulituba n. g. are described from the gills of the yellowfin goatfish Mulloidichthys vanicolensis (Valenciennes) off New Caledonia (South Pacific). Volsellituba and Pennulituba resemble dactylogyrid genera whose species lack eye-spots and possess tandem or slightly overlapping gonads, a single prostatic reservoir, a male copulatory organ without an accessory piece, a dextroventral non-sclerotised vagina, ventral and dorsal anchor/bar complexes, and hooks with shanks comprising a single slender unit. Volsellituba n. g. is characterised by its species having ventral tegumental folds at the level of the vaginal duct, a male copulatory organ with a subterminal basal opening and a two-piece dorsal bar. The following new species of Volsellituba are described: V. orchidea n. sp. (type-species), V. nabla n. sp. and V. elephantina n. sp. Pennulituba n. g. is distinguished by its species possessing a male copulatory organ with a wing-shaped membrane and a dorsal bar with a poorly to non-sclerotised medial part. This genus includes P. piratifalx n. sp. (type-species) and P. cymansis n. sp. A tabular summary of the species of Haliotrema Johnston & Tiegs, 1922 reported from mullids is provided.     

A new diplectanid (Monogenea) genus and species from the gills of the black snook, Centropomus nigrescens (Perciformes: Centropomidae) of the Pacific coast of Mexico

Cornutohaptor nigrescensi n. sp. (Diplectanidae) is described from the gills of the black snook, Centropomus nigrescens (Perciformes: Centropomidae) from the Pacific coast of Mexico. Cornutohaptor n. gen. is proposed for this new species and is characterized by possessing 2 intestinal ceca terminating blindly; a germarium looping right intestinal cecum; bilobed testis; 2 seminal vesicles; 7 pairs of hooks, each with protruding thumb; a grooved ventral bar and coiled male copulatory organ (MCO); an accessory piece comprising a "baglike structure" with an appendage; dorsal bars associated parallelly to body midline; and no adhesive accessory organs on the haptor. Cornutohaptor differs from all confamilial genera by including species with anchors with straight and deep root longest, hook pair 1 reduced in size, MCO with counterclockwise rings, and by the morphology of the accessory piece. Cornutohaptor nigrescensi most closely resembles species of Murraytrema Price, 1937, Lobotrema Tripathi, 1937, and Murraytrematoides Yamaguti, 1958, because of the absence of squamodiscs or lamellodiscs on the haptor and tegumental scales on the posterior portion of the body. Cornutohaptor differs from these genera in the position and number of haptoral bars (2 bars in Lobotrema spp., dorsal bars transversally associated in Murraytrema and Murraytrematoides spp.) and in having a coiled MCO (copulatory organ is a comparatively straight, poorly sclerotized tube in Murraytrematoides spp.). This is the first diplectanid described from a centropomid along the Pacific coast of Mexico.     

New species of Tereancistrum Kritsky,Thatcher & Kayton, 1980 (Monogenea: Dactylogyridae: Ancyrocephalinae) from the gills of Prochilodus lineatus (Osteichthyes: Prochilodontidae) from the upper Paraná River floodplain,Brazil

Two new species of Tereancistrum Kritsky, Thatcher & Kayton, 1980 are described from the gills of Prochilodus lineatus (Prochilodontidae) collected from the upper Paraná River floodplain, Brazil. T. toksonum n. sp. is characterised by a slim ventral bar with a sclerotised membrane along the anterior margin. Another characteristic is the dorsal anchor with an elongated deep root. T. curimba n. sp. is similar to T. ornatus Kritsky, Thatcher & Kayton, 1980 but possesses a sclerotised structure between the accessory sclerites of the ventral anchors. Moreover, the accessory anchor sclerites of this new species are longer than those described for T. ornatus.     

Monogeneans from the gills of glassfishes (Teleostei: Perciformes: Ambassidae) in India, with the proposal of Chandacleidus n. g. (Monogenea: Dactylogyridae)

Chandacleidus n. g. (Monogenea, Dactylogyridae) is proposed to include three species collected from the gills of Indian glassfishes (Ambassidae): Chandacleidus recurvatus (Jain, 1961) n. comb. (syn. Urocleidus recurvatus Jain, 1961) from Chanda nama and C. ranga (new host record) is redescribed; and Chandacleidus saiensis n. sp. and C. lucknowensis n. sp., both from Chanda nama and C. baculis, are described. Chandacleidus n. g. is characterised by species possessing: posteriorly united intestinal caeca; overlapping gonads (testis dorsal to ovary); a counterclockwise male copulatory organ; a grooved accessory piece; a dextro-marginal vaginal pore; a haptor with two lateral flaps and armed with dissimilar dorsal and ventral anchor/bar complexes and 14 similar hooks (dissimilar in size); and hook shanks comprised of two subunits.     

Neotropical Monogenoidea. 33. Three new species of Ancistrohaptor n. g. (Dactylogyridae,Ancyrocephalinae) on Triportheus spp. (Teleostei,Characidae) from Brazil,with checklists of ancyrocephalines recorded from neotropical characiform fishes

Three new species of Ancistrohaptor n. g. are described from the gills of three species of Triportheus (Characidae) collected from the environs of Manaus, Amazonas, Brazil: A. falcatum n. sp. from T. elongatus; and A. falciferum n. sp. and A. falcunculum n. sp. from T. angulatus, T. albus and T. elongatus. Ancistrohaptor n. g. is proposed for species possessing overlapping gonads, a dextral or dextroventral vaginal aperture, a coiled (counter-clockwise) male copulatory organ, two accessory pieces in the copulatory complex, and a haptor armed with two pairs of anchors (ventral anchor with elongate shaft), dorsal and ventral bars and 14 hooks; hook pair 1 (ventral) anterior to ventral bar, pairs 2–4 (ventral) lying bilaterally anterior to ventral anchor bases, pair 5 (ventral) associated with distal end of ventral anchor shafts, and pairs 6 and 7 (dorsal) bilateral about midway along haptoral length. Parasite-host and host-parasite lists of the Ancyrocephalinae from neotropical Characiformes are provided.     

Bucephaline digeneans (Bucephalidae) in <Emphasis Type="Italic">Sphyraena putnamae</Emphasis> Jordan &; Seale (Sphyraenidae) from the lagoon off New Caledonia

Lethrinitrema gibbus n. g., n. sp. and L. dossenus n. sp. are described from the fish Lethrinus rubrioperculatus Sato collected off New Caledonia, South Pacific. Members of Lethrinitrema n. g. (Ancyrocephalidae) are characterised by having two pyriform haptoral reservoirs and ventral anchors with lateral grooves. The elongate tubular distal end of each reservoir bifurcates, draining into a superficial lateral groove on each side of the ventral anchors. The haptoral reservoirs are postulated to store secretory products which assist in attachment to the host. Lethrinitrema spp. also possess tandem gonads, a male copulatory organ without an accessory piece or with thinly sclerotised accessory piece, and a dextrolateral, non-sclerotised vaginal bulb. The two new species have small, poorly demarcated haptors with small haptoral armament and a crown-like piece on the tip of the inner root of the ventral anchors. They differ from each other in the shape and size of the ventral bar and male copulatory organ (40–45 μm in length in L. gibbus vs 24–30 μm in L. dossenus). Three other species, previously included in Haliotrema Johnston & Tiegs, 1922, are transferred to Lethrinitrema, i.e. L. chrysostomi (Young, 1968) n. comb., L. fleti (Young, 1968) n. comb. (both briefly redescribed from paratypes) and L. lethrini (Yamaguti, 1937) n. comb. All species of Lethrinitrema parasitise Lethrinus spp. (Lethrinidae), and there is evidence for the existence of further Lethrinitrema spp. on Lethrinus spp. in the Indo-Pacific region.     

Dactylogyridae (Monogenea) from the gills of Iheringichthys labrosus (Osteichthyes: Pimelodidae) from the upper Paraná River floodplain,Brazil, with the proposal of Pseudovancleaveus n. g

Two new species of Demidospermus Suriano, 1983 and a new genus, Pseudovancleaveus, and species are described from the gills of Iheringichthys labrosus (Pimelodidae). The fishes were collected from the upper Paraná River floodplain, Brazil. D. mandi n. sp. is characterised by the distal region of the copulatoty organ having an expanded bulb and D. labrosi n. sp. by the copulatory organ having a funnel-shaped proximal extremity. The latter species also has an accessory piece comprising a variable sheath enclosing the distal shaft of the copulatory organ and two anterolateral structures resembling irregular spheres. Pseudovancleaveus paranaensis. n. g., n. sp. is characterised by a sinistral vagina, overlapping gonads, a copulatory ligament, anchors without a fold on the base and hooks with slightly inflated shanks. A new combination, Pseudovancleaveus platensis, is proposed for Vancleaveus platensis Suriano & Incorvaia, 1995.     

A new monogenean genus from an ephippid fish off Peninsular Malaysia

Sundatrema langkawiense n. g., n. sp. (Monogenea: Ancyrocephalidae) is described from the gills of the orbfish Ephippus orbis (Bloch) (Ephippidae) off the Island of Langkawi, Malaysia, in the Andaman Sea. This new genus has the ancyrocephalid characteristics of four anchors, 14 marginal hooks and two bars, but differs from other four-anchored monogenean genera, and notably from Parancylodiscoides Caballero & Bravo Hollis, 1961 (found on the ephippids Chaetodipterus spp. off Central and South America), by having a unique combination of features. These include a muscular genital sucker and a vas deferens and vagina on the same (sinistral) side of the body. It is similar to Parancylodiscoides in having four haptoral reservoirs opening at the anchoral apertures, four anchors, similar connecting bars and small marginal hooks. The new species is characterised by the above generic features and by possessing a small, short copulatory organ lacking an accessory piece. Diplectanum longiphallus MacCallum, 1915 (previously attributed to Ancyrocephalus Creplin, 1839, Tetrancistrum Goto & Kikuchi, 1917 and Pseudohaliotrema Yamaguti, 1953) is transferred to Parancylodiscoides as P. longiphallus (MacCallum, 1915) n. comb.     

Two new species of Gyrodactylus von Nordmann, 1832 (Monogenea: Gyrodactylidae) parasitizing Girardinichthys multiradiatus (Cyprinodontiformes: Goodeidae), an endemic freshwater fish from central Mexico

Gyrodactylus mexicanus n. sp. and Gyrodactylus lamothei n. sp. are described from the fins and skin of Girardinichthys multiradiatus, an endemic freshwater fish from central Mexico. Gyrodactylus mexicanus is compared to other Gyrodactylus species that parasitize Fundulus spp., the phylogenetically closest group to the Goodeidae from North America. Gyrodactylus mexicanus is distinguished by having large anchors with well-developed superficial roots, enlarged hooks with a proximally disrupted shank (ligament), and a ventral bar with 2 poorly developed anterolateral projections and a small medial process. Gyrodactylus lamothei is distinguished from G. mexicanus and from other species of Gyrodactylus on the North American continent by having anchors with a sclerite on the superficial root and robust hooks with a straight shaft and a recurved point.     

Morphological and molecular data of new species of Characithecium and Diaphorocleidus (Monogenea: Dactylogyridae) from Neotropical characid fishes

The present study describes three new species of monogenean parasites of characid fishes from the Upper Paraná River basin, Brazil: Characithecium paranapanemense n. sp. on Psalidodon paranae and Psalidodon bockmanni, Diaphorocleidus magnus n. sp. on Astyanax lacustris and Psalidodon fasciatus, and Diaphorocleidus neotropicalis n. sp. on Astyanax lacustris and P. bockmanni. An amendment for Diaphorocleidus is proposed, since additional characters observed in the new species required to extend the generic diagnostic features mainly to include: articulation process connecting the base of the MCO with accessory piece present or absent, and accessory piece with variable shapes (plate-like, pincer-shaped, wrench-shaped, sheath-shaped), divided or not into subunits. Characithecium paranapanemense n. sp. can be distinguished from other congeners by the morphology of its MCO and accessory piece. Diaphorocleidus magnus n. sp. differs from most of its congeners by the morphology of its accessory piece, the presence of articulation process connecting the base of the MCO with accessory piece, and the morphology of the sclerotized structures of the haptor. Diaphorocleidus neotropicalis n. sp. can be easily distinguished from its congeners by the morphology of the accessory piece, the sclerotized structures of the haptor and the morphology of the vagina. Molecular data of the new species (partial 28S rDNA and mitochondrial cytochrome oxidase I) were obtained and the first phylogenetic analysis based on 28S rDNA gene sequences for species of Characithecium and Diaphorocleidus are provided. Although Diaphorocleidus and Characithecium share some morphological similarities, phylogenetic analysis indicates that species of these two genera are not closely related.