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Ameloblastella martinae n. sp. is described from the gills of the pimelodid catfishes (Siluriformes: Pimelodidae) Sorubim lima (Bloch & Schneider) (type-host) and Hemisorubim platyrhynchos(Valenciennes) in the Peruvian Amazonia, and on Pseudoplatystoma corruscans (Spix & Agassiz) and P. recticulatum Eigenmann & Eigenmann in Argentina. The new species is distinguished from other congeners mainly by the morphology of the male copulatory organ (MCO), which has a form of acorkscrew with tight rings, whereas in other species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000, the MCO is formed by a delicate and coiled tube forming loose rings. Sclerotised structures (haptoral elements and MCO) of specimens of A. martinae n. sp. were used to compare two parasite populations (from Peru and Argentina) using Euclidean distances. Despite the geographical isolation and different hostassociations, both populations belong to the same species. The phylogenetic position of A. martinae n. sp. was analysed using partial sequences of the 28S mrDNA gene along with 46 species of dactylogyrid parasites of siluriforms (Siluriformes) under Maximum Likelihood (ML) and Bayesian Inference (BI) criteria. Phylogenetic reconstructions showed that Ameloblastella represented by five species, including its type-species A. chavarriai (Price, 1936) from the heptapterid Rhamdia guatemalensis and A. martinaen. sp., was recovered as a well-supported monophyletic group (in both analyses, ML and BI). An additional species, Ameloblastella sp., was found on P. corruscans and P. reticulatum in Argentina. The morphology of the MCO and haptoral elements suggests that Ameloblastella sp. may represent a new species. However, the few specimens found and the lack of genetic sequences of this species precluded its formal description. Fil: Mendoza Palmero, Carlos A.. Masaryk University. Faculty Of Sciences. Institute Of Botany And Zoology; República Checa Fil: Rossin, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Irigoitia, Manuel Marcial. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Scholz, Tomáš. University of South Bohemia; República Checa

Gyrodactylus mojarrae n. sp. is described from the gills of the Neotropical cichlids Thorichthys maculipinnis, Rocio octofasciata, Vieja zonata and V. fenestrata from several localities across southern Mexico. The new species is erected on the basis of the morphology of the haptoral elements (anchors, bars and hooks), and its phylogenetic position within the Gyrodactylidae is evaluated based on the analysis of partial sequences of the ITS1, 5.8 rRNA gene and ITS2. Gyrodactylus mojarrae n. sp. differs from other congeneric species by having hooks with a straight shaft and recurved point, pointed toe and convex heel, presence of reduced superficial anchor roots, by the number and disposition of spinelets of the male copulatory organ, and the absence of shield and lateral processes of the superficial bar. Molecular circumscription of isolates of G. mojarrae n. sp. from different host and hydrological basins showed that these isolates are conspecific and represent a distinct lineage from other congeners, including newly sequenced isolates of Gyodactylus sp. A and Gyrodactylus sp. B from Astyanax mexicanus (Characidae) and Gobiomorus dormitor (Eleotridae), respectively. Genetic affinities of Gyodactylus sp. A and B indicate that they might represent undescribed species infecting freshwater fish from the Americas.

Based on an integrative taxonomic approach, combining morphological characters and partial sequences of the 28S rRNA gene, a new genus and species, Parasciadicleithrum octofasciatum, is proposed to accommodate dactylogyrids infecting the gills of Rocio octofasciata (Cichlidae) from a tributary of the Lacantun River basin, Chiapas State, southern Mexico. Morphologically, the new genus resembles members of Sciadicleithrum (Dactylogyridae) in the presence of membranes on the anterior margins of both ventral and dorsal haptoral bars. However, Parasciadicleithrum octofasciatum n. sp. shows morphological differences with respect to a subset of species of Sciadicleithrum occurring in the same host group and geographic area, such as the body size and gonad dimensions (length and width of germarium and testis, respectively, smaller in the new genus). Phylogenetic analyses performed herein based on Maximum Likelihood and Bayesian Inference criteria, showed that Parasciadicleithrum octofasciatum n. sp. represents an undescribed taxon morphologically very similar to species of Sciadicleithrum from which it can be consistently distinguished on the basis of molecular data. P. octofasciatum n. sp. appeared genetically distant from Sciadicleithrum spp. and nested with dactylogyrid parasites of African cichlids. Parasciadicleithrum n. gen. showed divergence levels in the 28S rDNA sequences of 25–26% with respect to Sciadicleithrum spp. Therefore, on the basis of molecular evidence mainly, and morphological differences highlighted above, the erection of the new genus is proposed. The evolutionary and ecological factors that may have influenced the associations between Neotropical cichlids and their dactylogyrid parasites are briefly discussed.

Nanayella gen. n. is proposed to accommodate four new species of dactylogyrid monogeneans found on the gills of two species of pimelodid catfishes (Siluriformes) from the Amazon River basin in Peru and the Upper Paraná River basin in Brazil. Nanayella gen. n. is mainly characterised by the presence of modified hook pairs 5 and 6, which have a slender shank with slightly enlarged base, inconspicuous thumb, and straight point. Nanayella aculeatrium gen. n. et sp. n. (type species) from Sorubim lima (Bloch et Schneider) (type host) differs from its congeners mainly by possessing seven sclerotised spines on one side of circular ornamentation of the vaginal atrium. Nanayella fluctuatrium gen. n. et sp. n. is characterised by the presence of sclerotised undulations surrounding the circular ornamentation of the vaginal atrium. Nanayella amplofalcis gen. n. et sp. n. is typified by possessing hook pairs 1 and 2 with a robust, wide shank and a round, weakly sclerotised subunit at the base. Nanayella processusclavis gen. n. et sp. n. differs from congeners by the presence of a conspicuous posterior medial process on the dorsal bar. Urocleidoides megorchis Mizelle et Kritsky, 1969 described from the gills of S. lima in Brazil is transferred to Nanayella gen. n. as Nanayella megorchis comb. n. based on morphological and molecular evidence. Analyses of partial sequences of the 28S rRNA gene revealed all five species of the new genus to form a monophyletic clade within a bigger clade comprised of dactylogyrids of South American pimelodids.

On the basis of morphological and molecular data, Walteriella n. g. is proposed to accommodate the dactylogyrid parasites Walteriella conica n. sp. (type-species) from the gills of Platynematichthys notatus (Jardine) (type-host) and Brachyplatystoma juruense (Boulenger), and Walteriella ophiocirrus n. sp. from the gills of Platystomatichthys sturio (Kner) (type-host), all fish host belonging to the Pimelodidae collected in the Peruvian Amazonia. Species of the new genus are distinguished from other dactylogyrids infecting Neotropical catfishes by the presence of a folded germarium, a male copulatory organ basally articulated to the accessory piece, a cone-shaped seminal receptacle, and ventral and dorsal bars with projections directed anteriorly. Both species of the new genus form a strongly supported lineage closely related to Dactylogyridae gen. sp. 13, a parasite of Hypophthalmus edentatus Spix & Agassiz (Pimelodidae) in an analysis of partial sequences of the 28S rRNA gene. The clade formed by species of Walteriella n. g. and Dactylogyridae gen. sp. 13 is closely related to other dactylogyrids infecting pimelodid catfishes. Based on the morphology of its haptoral elements and copulatory complex, the species Dactylogyridae gen. sp. 13 is morphologically different from species of Walteriella n. g., but its generic assignment is still unclear.

During a research on gill ectoparasites of siluriform fishes from the Peruvian Amazonia, the following monogeneans were found: Ameloblastella edentensis n. sp. from Hypophthalmus edentatus Spix & Agassiz; Ameloblastella peruensis n. sp. from Hypophthalmus sp.; Ameloblastella formatrium n. sp. from Pimelodidae gen. sp. (type-host) and Duopalatinus cf. peruanus Eigenmann & Allen; Ameloblastella unapioides n. sp. from Sorubim lima (Bloch & Schneider) (type-host) and Pimelodus sp; Cosmetocleithrum tortum n. sp. from Nemadoras hemipeltis (Eigenmann); and Cosmetocleithrum bifurcum n. sp. from Hassar orestis (Steindachner) (both Doradidae). All new species described herein are mainly differentiated from their congeners based on the morphology of the copulatory complex. The pimelodids H. edentatus and S. lima, and the doradids N. hemipeltis and H. orestis represent new hosts species for species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 and Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986, respectively. The morphological diagnosis of the present species of Ameloblastella and Cosmetocleithrum also supported by a previous molecular analysis of these species is briefly discusssed herein.

Three new species of gill monogeneans (Dactylogyridae: Ancyrocephalinae) are described from siluriform catfish from Iquitos, Peru: Demidospermus mortenthaleri n. sp. from Brachyplatystoma juruense (Boulenger), Demidospermus brevicirrus n. sp. from Pimelodus sp., and Aphanoblastella aurorae n. sp. from Goeldiella eques (MüllerTroschel). Demidospermus mortenthaleri is characterized by a male copulatory organ (MCO) with a small loop at its middle portion; 2 types of hooks, of which pairs 5 and 6 are longer than the remaining hooks; a proximal subunit round and highly depressed thumb; and a sclerotized vagina with a round pad at the vaginal aperture. Demidospermus brevicirrus is distinguished from other congeners by the presence of a short, straight, and robust MCO and boot-shaped accessory piece with a hooked projection directed posteriorly. Aphanoblastella aurorae is the only species of the genus that possesses an arrow-shaped sclerotized vagina and a medial process on the dorsal bar. Another 6 dactylogyrids described previously are recorded for the first time from the Peruvian Amazonia: Cosmetocleithrum bulbocirrus Kritsky, Thatcher and Boeger, 1986 ; Vancleaveus fungulus Kritsky, Thatcher and Boeger, 1986 ; V. janauacaensis Kritsky, Thatcher and Boeger, 1986 ; V. platyrhynchi Kritsky, Thatcher and Boeger, 1986 ; Unilatus unilatus Mizelle and Kritsky, 1967 ; and U. brittani Mizelle, Kritsky and Crane, 1968 . Based on observations of specimens collected in the Peruvian Amazonia, new morphological data for these species are provided. Comparison of new specimens of U. unilatus and U. brittani with those of Unilatus brevispinus Suriano, 1985 and Unilatus longispinus Suriano, 1985 , both originally described from Brazil, has shown that they are conspecific. Therefore, the latter species were synonymized with U. unilatus and U. brittani , respectively. In addition, 56 undescribed monogeneans found in catfish from the Peruvian Amazonia, some of them probably belonging to new genera, are listed.

Three new species of Demidospermus Suriano, 1983 were found in mixed infections on the gills of 4 pimelodid catfish collected in the Amazon River basin around Iquitos, Peru, namely, Demidospermus peruvianus n. sp. from Pimelodus ornatus Kner, Pimelodus blochii Valenciennes, Pimelodus sp. (type host), and an unidentified pimelodid. Demidospermus peruvianus n. sp. (type host, Pimelodus sp.) is characterized by the presence of the male copulatory organ with 2 lateral, thickened projections, and the vagina with a loop at its middle. Demidospermus curvovaginatus n. sp. from P. ornatus , Pimelodus sp. (type host), and Pimelodidae gen. sp. differs from its congeners by the presence of a funnel-shaped vagina directed posteriorly and a male copulatory organ with a small lateral projection at its base. Demidospermus striatus n. sp. from P. blochii and Pimelodus sp. (type host) is distinguished by a cup-shaped vagina with conspicuous ridges at the perimeter of the aperture with a short tube directed anteriorly. In addition, Urocleidoides lebedevi Kritsky and Thatcher, 1976 , a parasite originally described from the gills of Pimelodus grosskopfii (type host) from Colombia, is transferred to Demidospermus , based on morphological characters that we observed in type specimens.