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.

Brazil is a megadiverse country and is participant of fundamental environmental agreements for biodiversity conservation. However, the internal politics and the cultures that affect negatively the ecological integrity in Brazilian freshwater need to be improved on the condition of sustainable management. Scientific community, the government and stakeholders are in constant conflicts of goals. Meanwhile, the current model for Brazilian aquaculture shows problems of ecological impact due to the lack of appropriated planning and legislation to the aquatic biota. The non‐recognition of sustainable census incorporated in its environmental politics reflects in an archaic and unsustainable management, with the following characters: a non‐specific approach for technical management, the indiscriminate use of interspecific hybrids and non‐native species and the lack of skilled labour. The potential impact on native species and the introduction of pathogens are the main negative effects on aquatic biota. This way, the aim of this article is to elucidate the conflicts of interests and ecological effects of fish aquaculture in Brazil, besides providing good practices and sustainable alternatives for management.

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.

Urocleidoides spp. are reported from the gills of 20 specimens of Parodon nasus (standard length 8.5–12 cm), from the Indiana stream, Tietê River, Upper Paraná River basin, municipality of Botucatu, São Paulo State, Brazil. Urocleoidoides tenuis and two new species were found. Urocleidoides indianensis n. sp. differs from its congeners mainly by the morphology of the vaginal sclerite that is robust, sickle-shaped, and forked at the distal end; and by the bulbous-shaped accessory piece of the male copulatory complex. Urocleidoides parodoni n. sp. resembles U. tenuis by presenting male copulatory organ with approximately 7 ½ counterclockwise rings, but differs by the morphology of the accessory piece (lobate with a small hook-like projection versus pincer-shaped), vaginal sclerite (thumb-like subterminal projection vs. presence of a distal hook), vaginal tube (conspicuously sclerotized vs. slightly sclerotized), shape of the ventral bar (bowed vs. wide V-shaped), ventral and dorsal anchors (robust base and short shaft vs. considerably less robust base and long shaft), and hooks (slender shank with a weakly sclerotized subunit at base vs. dilated shank). Sequences of the partial 28S rDNA gene of the dactylogyrids found in this study are provided. Phylogenetic analyses showed Urocledoides spp. from Parodontidae clustering together with strong support values. This study increases the number of valid Urocleidoides species to 39, and the number of species described from parodontid hosts to four.

Heteropriapulus Kritsky, 2007 (Monogenea: Dactylogyridae), which originally included only two species from the gills of loricariid catfishes, is reviewed and six newly described species from loricariids in the Paraná River basin in Brazil are added. Diagnosis of the genus is amended and a key to the species identification is provided. Heteropriapulus anchoradiatus n. sp. from Pterygoplichthys ambrosettii (Holmberg) (Hypostominae) differs from its congeners by having a long sclerotized vagina, ventral anchors with short shaft and conspicuous superficial root, and a conspicuous and robust postero-medial process on the dorsal bar; H. bitomus n. sp. from the same fish host differs by the presence of two pairs of sclerotized patches associated with the ventral anchors; H. falxus n. sp. from Hypostomus strigaticeps (Regan) (Hypostominae) and Hypostomus ancistroides (Ihering) (Hypostominae) is unique by the shape of the accessory piece composed of two strongly sclerotized subunits; H. microcleithrus n. sp. from P. ambrosettii differs by presenting the smallest length of the dorsal bar and unique shape of the longer subunit of the accessory piece resembling the ‘hammer and sickle’ shape; H. pterygoplichthyi n. sp. from the same host presents unique shape of the longer subunit of the accessory piece of the cirrus, which is represented by ‘two sickles’ jointed by the base; and H. semitortus n. sp. from Rhinelepis aspera Spix & Agassiz (Rhinelepinae) can be distinguished by the accessory piece composed of a single straight unit and a cirrus tube with the highest number of spiral rings at the proximal end (2½). First molecular data for this genus (partial sequences of the 28S rRNA gene) are provided including the type species H. heterotylus (Jogunoori, Kritsky & Venkatanarasaiah, 2004).

A complete morphological description, supported by molecular data, of Clinostomum detruncatum metacercariae is reported in this study. The metacercariae were found infecting Synbranchus marmoratus from the Paraná River, municipality of Guaíra, Paraná State, Brazil. The taenioidean uterus is the main morphological characteristic of this species. Both neighbor-joining (NJ) and maximum likelihood (ML) trees showed 2 clear separate clusters grouping together the species from the Palearctic region (Clinostomum complanatum, Clinostomum cutaneum, Clinostomum phalacrocoracis, Clinostomum philippinense) and those from the Nearctic/Neotropical regions (Clinostomum marginatum, Clinostomum tataxumui, C. detruncatum, Clinostomum sp. 7). The latter clade is divided into 2 subclades grouping species from North America and Mexico (C. marginatum and C. tataxumui), and those from Brazil (C. detruncatum and Clinostomum sp. 7).

The purpose of this study was to evaluate the helminth fauna of Steindachnerina insculpta in the Taquari River, a tributary of the Jurumirim reservoir in the state of São Paulo, and to investigate whether some helminth species may act as a bioindicator of environmental impact. The host fish sample was composed of 60 specimens, with 30 individuals sampled in a lotic stretch and 30 in a lentic stretch. The following were found: the monogeneans Anacanthoroides mizelli, Diaphorocleidus kabatai, Urocleidoides sp. and Euryhaliotrema chaoi; the digenean Sphincterodiplostomum musculosum and unidentified metacercariae; the nematode Travnema travnema and unidentified larvae; and the acanthocephalan Gorytocephalus plecostomorum. The total prevalence of monogeneans (z = 3.14; p = 0.002) and A. mizelli (z = 3.879; p ≤ 0.001), as well as the mean abundance of total monogeneans (U = 642.0; p ≤ 0.001) and A. mizelli (U = 623.5; p ≤ 0.001), were higher in the lentic stretch. Steindachnerina insculpta and its monogeneans comprise a potential group that could be used to investigate environmental impact, as demonstrated in this study.Keywords: Neotropical fish, teleost, parasites, bioindicator, reservoir. ResumoO objetivo desde estudo foi avaliar a helmintofauna de Steindachnerina insculpta no rio Taquari, um tributário do reservatório de Jurumirim, estado de São Paulo, e verificar se alguma espécie pode agir como bioindicadora de impacto ambiental. A amostragem de peixes foi composta de 60 espécimes, com 30 indivíduos amostrados no trecho lótico e 30 no trecho lêntico. Foram encontrados os monogenóides: Anacanthoroides mizelli, Diaphorocleidus kabatai, Urocleidoides sp. e Euryhaliotrema chaoi; o digenético Sphincterodiplostomum musculosum e metacercárias não identificadas, o nematoide Travnema travnema e larvas não identificadas; e o acantocéfalo Gorytocephalus plecostomorum. A prevalência total de monogenóides (z = 3,14; p = 0,002) e A. mizelli (z = 3,879; p ≤ 0,001) e também a abundância média de monogenóides total (U = 642,0; p ≤ 0,001) e A. mizelli (U = 623,5; p ≤ 0,001) foram maiores no trecho lêntico. Steindachnerina insculpta e seus monogenóides compõem um grupo em potencial que pode ser usado para investigar impactos ambientais, como mostrado neste estudo.

The viviparous gyrodactylid genus Macrogyrodactylus Malmberg, 1957 is endemic to Africa, composed of nine species from hosts of four freshwater fish families, including catfishes (Siluriformes: Clariidae). Three species, Macrogyrodactylus clarii Gussev, 1961; M. congolensis (Prudhoe, 1957) and M. karibae Douëllou et Chishawa, 1995, are primarily known to parasitise the African sharptooth catfish Clarias gariepinus (Burchell) in various African countries. From November 2017 to September 2019, a total of 184 individuals of C. gariepinus were collected from selected localities in southern Africa and their skin, fins and gills were surveyed for monogeneans. Three species of Macrogyrodactylus (M. clarii, M. congolensis and M. karibae) were found parasitising C. gariepinus from five localities in South Africa and Zambia. Overall prevalence was 50% to 100% with intensities of up to 109 parasites per host individual. New locality records in southern Africa, morphological observations and additional molecular data on the complete Internal Transcriber Spacer (ITS-1-5.8S-ITS-2) regions of the rDNA gene for the three gyrodactylid species are presented in this study.