Phylogenomics, evolution of trophic traits and divergence times of hemiodontid fishes (Ostariophysi: Characiformes).

The South American characiform family Hemiodontidae comprises five genera and 34 species. The family lacks comprehensive phylogenetic hypotheses resolving its species relationships. The studies that addressed these questions exhibited a narrow taxon sampling or used single-locus markers. Herein we surveyed hundreds of ultraconserved elements (UCEs) loci to provide the first molecular phylogenetic hypothesis and divergence time estimates for hemiodontids encompassing all its genera and most species (27 of the 34 valid species). We also tracked the history of the protractile upper jaw in the genera Argonectes and Bivibranchia across the recovered phylogenies through ancestral state reconstruction. Our results corroborate the monophyly of Hemiodontidae and the genera Argonectes and Bivibranchia in all phylogenetic methods with maximum clade support. The genera Anodus and Hemiodus were not monophyletic because Anodus elongatus was sister to the monotypic Micromischodus instead of A. orinocensis, and H. immaculatus did not form a clade with its other congeners, but instead was sister to the clade including Anodus and Micromischodus. All remaining species of Hemiodus were placed together into a monophyletic group, where they were arranged into four major subclades. The relationship in the family is summarised as: (Bivibranchia, (Argonectes, ((H. immaculatus, (Anodus, Micromischodus)), Hemiodus clade))), in discordance with the morphological phylogeny that placed all genera monophyletic and resolved the family as: ((Anodus, Micromischodus), (Hemiodus, (Argonectes, Bivibranchia))). The origin of Hemiodontidae was estimated from the Late Cretaceous to the Middle Paleogene, with the mean age in the Paleocene, while the origin of most hemiodontid genera except Bivibranchia occurred in the Miocene. Unordered parsimony and likelihood reconstruction indicates that Argonectes and Bivibranchia developed their protractile upper jaw independently.

Two new species of Hypostomus suckermouth-armoured catfishes (Teleostei: Loricariidae) from central Brazil.

This study describes two new endemic Hypostomus species from central Brazil, which were previously identified as genetically distinct lineages in a recent genomic study that recommended their testing and potential description based on morphological data. A machine learning classification procedure (random forest) was used to investigate morphological variation and identify putatively diagnostic characters for these candidate species and revealed that each is morphologically distinct. The new species Hypostomus cafuringa is characterized by small size, dark spots under a light background, deeper caudal peduncle and shorter first ray of the pectoral fin and base of the dorsal fin when compared to congeneric species from the region. H. cafuringa is known from the headwaters of the Maranhão River, upper Tocantins River basin, Distrito Federal, Brazil. The second new species, Hypostomus crulsi, is characterized by dark spots under a light background, absence of plates along the abdomen region, shorter first ray of the pelvic fin, shorter first ray of the pectoral fin and smaller body size. H. crulsi is known from the headwaters of the São Bartolomeu River, upper Paraná River basin, Distrito Federal, Brazil. The rapid conversion of natural habitats for agricultural development and the isolation of protected areas represent a serious threat to the continued existence of these two newly described endemic species, which warrant conservation assessment.

Molecular species delimitation of the genera Anodus, Argonectes, Bivibranchia and Micromischodus (Ostariophysi: Characiformes)

ABSTRACT A good taxonomic assessment of specimens is an essential task to many biological studies and DNA data have provided additional sources of information to assist in the disentanglement of taxonomic problems among living organisms, as has been the case of some taxa of the megadiverse Neotropical ichthyofauna. Here we assessed all valid species in the Neotropical freshwater fish genera Anodus, Argonectes, Bivibranchia and Micromischodus of the family Hemiodontidae to establish molecular species boundaries among them. All species delimitation methods defined exactly only one MOTU for Anodus elongatus, Argonectes longiceps, A. robertsi, Bivibranchia bimaculata, B. notata, B. velox, and Micromischodus sugillatus, resulting in total congruence between nominal species and MOTUs for these seven taxa. The three species having discordant results across analyses: Anodus orinocensis, Bivibranchia fowleri, and Bivibranchia simulata, matched more than one MOTU per species in some methods, meaning that cryptic diversity may exist within these taxa. Overall, this great correspondence among morphological and molecular boundaries for thae species analysed seem to be indicative of a reasonably stable taxonomy within these Hemiodontidae genera.

RESUMO Uma avaliação taxonômica adequada dos espécimes é uma tarefa essencial para muitos estudos biológicos, e os dados de DNA têm fornecido fontes adicionais de informações para auxiliar no desemaranhamento de muitos grupos taxonômicos, como tem sido o caso de alguns táxons da megadiversa ictiofauna Neotropical. Aqui examinamos todas as espécies válidas dos gêneros de peixes Neotropicais de água doce Anodus, Argonectes, Bivibranchia e Micromischodus (família Hemiodontidae) para estabelecer limites moleculares entre elas. Todos os métodos de delimitação definiram exatamente apenas uma MOTU para Anodus elongatus, Argonectes longiceps, A. robertsi, Bivibranchia bimaculata, B. notata, B. velox e Micromischodus sugillatus, resultando em congruência total entre espécies nominais e MOTUs para estes sete táxons. As três espécies com resultados divergentes entre as análises, a saber, Anodus orinocensis, Bivibranchia fowleri e Bivibranchia simulata, corresponderam a mais de um MOTU por espécie em alguns métodos, mostrando que pode existir uma diversidade críptica dentro desses taxa. No geral, esta grande correspondência entre os limites morfológicos e moleculares para as espécies analisadas parece indicar uma taxonomia relativamente estável para esses gêneros de Hemiodontidae.

Ontogenetic Development Related to Parental Care of a Neotropical Fish, Pterygoplichthys ambrosettii (Siluriformes: Loricariidae).

This study describes the main ontogenetic changes in the armored catfish Pterygoplichthys ambrosettii from newly hatched larva to adult. The relationship between the degree of development of newly hatched larvae and post-larvae and parental care is discussed. Ontogenetic series containing newly hatched larvae, post-larvae, and juveniles of P. ambrosettii were obtained from the Fish Culture Station of Universidade Estadual Paulista. Adult specimens were collected from the Preto River in the upper Paraná River basin. Morphological, osteological, morphometric, and meristic data and color pattern were analyzed. The species exhibited indirect development, with a distinct post-larval stage after the larval stage. Newly hatched larvae had a well-developed yolk sac and lacked pigmentation. The following characters underwent less change during development and can therefore be useful in taxonomical analyses: odontodes located posteriorly to the preopercle, number of plates on the lateral line, lower lip with three series of papillae, spots on the upper ray of the caudal fin, caudal fin similar to that of the adult, body ventrally covered with dermal plates and odontodes, small irregular spots on head, and typical ventral color pattern of the adult. The morphometric data revealed that most variation in body proportions occurred during less advanced developmental stages. Parental care influenced the ontogenetic development of newly hatched larvae.

Stream fish from recently deforested basins in the Meridional Amazon, Mato Grosso, Brazil / Peixes de riachos de bacias recentemente desmatadas na Amazônia Meridional, Mato Grosso, Brasil

Abstract: The replacement of tropical forests to production systems is one of the leading causes of riverine ecosystem alterations. However, current assemblages' composition may also result from the time since these transformations have begun. Therefore, the knowledge of diversified historical scenarios can facilitate the accomplishment of actions that involve the aquatic environments recovery. In this study, an inventory of stream fish was carried out in basins whose deforestation was intensified in the last 20 years, to compose a baseline for ecological and taxonomic studies. The habitat, physical and chemical variables, and the fish assemblages from 60 streams in the northwest region of the state of Mato Grosso, in the Aripuanã and Juruena river basins, were sampled with standardized procedures. For a total of 130 species, a numerical predominance of small-sized Characidae and great rarity were registered, with 50 species represented by less than ten individuals and 19 singletons. Approximately 15% of the sampled taxa were identified only at the generic level, and for several taxa, more detailed taxonomic and molecular studies are required in order to achieve satisfactory identifications. None threatened species were so far reported. On the other hand, two specimens of non-native species were sampled. Although habitat quality is higher in forested streams, no differences in the species richness were registered when compared to the pasture with riparian forest streams or to more deforested streams. However, abundance was greater in these last two streams groups as a result of small-sized characins dominance.

Resumo: A substituição de florestas tropicais por sistemas de produção representa uma das principais fontes de alteração nos ecossistemas de riachos. Contudo, a composição atual das assembleias também depende do tempo decorrente desde o início dessas transformações e, desta forma, o conhecimento de cenários históricos variados pode facilitar a realização de ações que envolvam a recuperação de ambientes aquáticos. Neste estudo, foi realizado o inventário dos peixes de riachos em bacias cujo desmatamento foi intensificado nos últimos 20 anos, para compor uma linha de base que possa ser usada em estudos ecológicos e taxonômicos. Foram amostradas as variáveis do hábitat, físicas e químicas e os peixes de 60 riachos da região noroeste do estado de Mato Grosso, nas bacias dos rios Aripuanã e Juruena. No total, 130 espécies foram registradas, com predominância numérica de pequenos caracídeos e grande número de espécies raras, sendo 50 espécies representadas por menos que dez indivíduos e 19 por apenas um indivíduo. Aproximadamente 15% dos táxons amostrados foram identificados somente no nível genérico e vários precisam de estudos taxonômicos e moleculares mais detalhados para alcançar identificações satisfatórias. As espécies não-nativas foram representadas por dois exemplares e nenhuma espécie sabidamente ameaçada foi registrada. Embora a qualidade do hábitat seja superior nos riachos florestados, não houve diferenças na riqueza das assembleias quando comparada aos riachos de microbacias de pastagem, porém com faixa ripária florestada, ou com maior desmatamento. Contudo, a abundância foi maior nesses dois grupos de riachos, como resultado da dominância de caracídeos de pequeno porte.

Checklist and key for the identification of fish fauna of the Uberaba River, Upper Paraná River system, Brazil.

The Uberaba River is an important right-bank tributary to the Grande River, in the Upper Paraná River system, Brazil, and the main water source for the public supply of the Uberaba city, Minas Gerais state. An inventory, an identification key, and photographs of the fish species of the Uberaba River are provided, based on samples made between 2012 and 2014 at 14 sampling sites in the river system. A total of 73 species was recorded from six orders, 20 families, and 49 genera. Characiformes and Siluriformes are the most speciose orders and Characidae and Loricariidae are the most commonly recorded families. Most species are autochthonous, nine are considered allochthonous, and two species are exotic. The Uberaba River has a diverse and heterogeneous ichthyofauna, typical of rheophilic environments, with endemic species and few non-native species.

DNA barcode and minibarcode identification of freshwater fishes from Cerrado headwater streams in Central Brazil.

The extraordinary species diversity of the Neotropical freshwater fish fauna is world renown. Yet, despite rich species diversity, taxonomic and genetic resources for its Cerrado ichthyofauna remain poorly developed. We provide a reference library of 149 DNA barcodes for 39 species/lineages of Cerrado headwater stream fishes from the Brazilian Distrito Federal and nearby areas and test the utility of distance-based criteria, tree-based criteria and minibarcodes for specimen identification. Mean Kimura 2-parameter genetic distances within species to orders ranged 1·8-12·1%. However, mean intraspecific v. congeneric-interspecific distances (0·9-1·3%) overlapped extensively and distance-based barcoding failed to achieve correct identifications due to c. 4-12·1% error rates and 19·5% ambiguous identifications related to the presence of singletons. Overlap was reduced and best-match success rates improved drastically to 83·5% when Characidium barcodes representing potential misidentifications or undescribed species were removed. Tree-based monophyly criteria generally performed similarly to distance methods, correctly differentiating up to c. 85% of species/lineages despite neighbour-joining and Bayesian tree errors (random lineage-branching events, long-branch attraction). Five clusters (Ancistrus aguaboensis, Characidium spp., Eigenmannia trilineata, Hasemania hanseni and Hypostomus sp. 2) exhibited deep intraspecific divergences or para-/polyphyly and multiple Barcode Index Number assignments indicative of putative candidate species needing taxonomic re-examination. Sliding-window analyses also indicated that a 200 bp minibarcode region performed just as well at specimen identification as the entire barcode gene. Future DNA barcoding studies of Distrito Federal-Cerrado freshwater fishes will benefit from increased sampling coverage, as well as consideration of minibarcode targets for degraded samples and next-generation sequencing.

Hemiodus bimaculatus, a new species of Hemiodontidae from the Rio Tapajós drainage, Brazil (Ostariophysi: Characiformes).

Hemiodus bimaculatus sp. nov., is described from tributaries of the Rio Juruena and Rio Teles Pires in the upper Rio Tapajós basin. The new species is diagnosed from most congeners, except Hemiodus jatuarana, by having a conspicuous circular or horizontally elongate dark blotch on the caudal peduncle (v. inconspicuous in H. iratapuru and absent in the other species). The new species differs from H. jatuarana by having a round midlateral spot on the flank (v. absent in H. jatuarana), 98-121 perforated scales in the lateral line (v. 66-72 in H. jatuarana), 23-28 scale series above and 14-19 below lateral line (v. 12-13 above and 6-7 below in H. jatuarana). Hemiodus bimaculatus is hypothesised to be related to species of the H. microlepis group, from which it also differs by having 11-25 epibranchial (v. 26-34 in H. argenteus, 29-39 in H. microlepis, 21-42 in H. orthonops and 27-35 in H. parnaguae) and 18-31 ceratobranchial (v. 38-50 in H. argenteus, 43-58 in H. microlepis, 32-52 in H. orthonops and 34-48 in H. parnaguae) gill rakers in the first arch.

Poor taxonomic sampling undermines nomenclatural stability: A reply to Roxo et al. (2019).

A recent study based on genomic data by Roxo et al. (2019) provided a phylogeny of the Loricariidae, the largest catfish family and second largest Neotropical fish family with approximately 1,000 species. The study represents a valuable and innovative contribution for understanding higher-level relationships within the family. The phylogenetic tree inferred by Roxo et al. (2019) thoroughly corroborates the monophyly and relationships of most currently accepted subfamilies of Loricariidae, based on a fair taxon sampling (nearly 14% of the species in the family) representing most genera of each but one of the subfamilies, the Lithogeninae, the sister-group of the remaining members of the family (Pereira & Reis, 2017; Reis et al., 2017). In addition to a hypothesis of relationships, Roxo et al. (2019) also proposed a series of lower-level taxonomic changes, which are deemed premature considering that the taxonomic sampling of the study targeted higher-level clades, and go against one of the pillars of biological classification: nomenclatural stability (e.g., Heterick & Majer, 2018; Beninger & Backeljau, 2019). Here we (1) discuss implications of inadequate taxonomic sampling as a basis for changes in classification of species; (2) explain why the taxonomic sampling design of Roxo et al. (2019) is inadequate for the proposed nomenclatural changes; and (3) advocate that changes to classifications must be grounded on phylogenies with dense sampling of taxa at the relevant level.

Redescription of Trichomycterus striatus (Meek Hildebrand, 1913) (Siluriformes: Trichomycteridae), with notes on its geographic distribution.

Trichomycterus striatus is herein redescribed, based on examination of the types and recently collected specimens, and its geographic distribution is updated. This species can be diagnosed from all other northeastern South American congeners by its variable coloration pattern consisting of a yellowish to light brown background with a black lateral band and/or small dark brown spots on sides or uniformly light brown and by the following combination of characters: teeth conical arranged in three to four irregular rows in both jaws; anterior section of infraorbital canal (sensory pores i1 and i3) present; sensory pores s6 paired, 11-23 opercular odontodes; 27-44 interopercular odontodes; seven to eight pectoral-fin branched rays; 36-37 free vertebrae; 12-14 ribs; cleithrum pierced by several foramina; and caudal fin truncate to rounded. Trichomycterus striatus occurs from southern Costa Rica [from the Pirrís (herein reported for the first time), Térraba and Coto River basins] to eastern Panama (in most of the main river basins in both the Pacific and Atlantic versants), being the sole representative of the family in lower Central American waters.

Gross brain morphology of the armoured catfish Rineloricaria heteroptera, Isbrücker and Nijssen (1976), (Siluriformes: Loricariidae: Loricariinae): A descriptive and quantitative approach.

The gross morphology of the brain of Rineloricaria heteroptera and its relation to the sensory/behavioural ecology of the species is described and discussed. The sexual and ontogenetic intraspecific variation in the whole brain length and mass, as well as within/between the eight different brain subdivisions volumes, is also examined and discussed. Negative allometry for the whole brain length/mass and relative growth of the telencephalon and optic tecta was observed. Positive allometry was observed for the relative growth of the olfactory bulbs and medulla oblongata. Univariate and multivariate statistical analyses did not reveal significant differences in the brain subdivision growth rates among sexes and/or developmental stages, except for the optic tectum and some portions of the medulla oblongata, with juveniles and males showing more developed optic tecta and medullary subdivisions, respectively. The growth rates for each brain subdivision were relatively constant, and the slopes of the growth equations were almost parallel, except for those of the olfactory bulbs and medulla oblongata subdivisions, suggesting some degree of tachyauxesis of subdivisions against the entire brain. The corpus cerebelli was the more voluminous brain subdivision in most specimens (principally adults), followed by the optic tectum (the more voluminous subdivision in juveniles), hypothalamus, and telencephalon, in that order. Differences in the number of lamellae and relative size of the olfactory organ were also detected among developmental stages, which were more numerous and larger in adults. Based on these results, it is possible to infer an ontogenetic shift in the habitat/resource use and behaviour of R. heteroptera. Vision, primarily routed through the optic tectum, could be fundamental in early stages, whereas in adults, olfaction and taste, primarily routed through the olfactory bulbs and medulla oblongata, play more important roles.

Microlepidogaster negomata, a new hypoptopomatine catfish (Loricariidae: Hypoptopomatinae) from Rio São Francisco basin, southeastern Brazil.

The number of species of Microlepidogaster recently increased considerably, the genus presently comprises six species distributed in the Paraná, São Francisco, and Jequitinhonha river basins. A new species of Microlepidogaster is herein described from the upper Rio São Francisco basin, which can be distinguished from all congeners by having two exclusive features within the genus: skin over swimbladder opening with two to five reduced unperforated platelets, and ventral laminar expansion of coracoid enclosing completely or almost completely the arrector fossa of the pectoral girdle. In addition, other features to recognize this species are: snout covered by many small plates bearing slender pointed odontodes; presence of iris operculum; exposure of pectoral girdle restricted to the lateral portion; presence of pectoral axillary slit only in juveniles; anterior portion of compound supraneural plus first dorsal-fin proximal radial contacting the neural spine of the eighth or ninth vertebra; first anal-fin pterygiophore covered only by skin; and uninterrupted, long median and mid-dorsal series of lateral plates.

A new species of Ituglanis (Siluriformes: Trichomycteridae) from the Tocantins and Paranaíba river basins, central Brazil, with remarks on the systematics of the genus.

Ituglanis goya, new species, is described from the Paranaíba and Tocantins river drainages, central Brazil. This is the first species of the genus described for the Upper Paraná system and the second epigean Ituglanis for the Tocantins basin. The new species is distinguished from its congeners by the combination of a color pattern formed by longitudinal stripes and spots, absence of the anterior cranial fontanel, pattern of the cephalic laterosensory system and several fin-ray counts. Ituglanis goya exhibits morphological features that oppose the traditional hypotheses of alignment of the genus with the TSVSG clade of Trichomycteridae. These and other issues concerning the systematics of Ituglanis and the Trichomycterinae are critically discussed.

Reconciling more than 150 years of taxonomic confusion: the true identity of Moenkhausia lepidura, with a key to the species of the M. lepidura group (Characiformes: Characidae).

Moenkhausia lepidura (Kner) is redescribed based on the examination of the type and other specimens from several localities of the Amazon and Orinoco basins. The species is readly diagnosed from congeners by a combination of a dark blotch on the upper caudal-fin lobe, lower lobe hyaline, and by the arrangement of predorsal scales, in which scales of anterior portion of predorsal area are arranged in pairs, followed by a single median row of scales extending to dorsal-fin origin. The analysis of the type material of Gymnotichthys hildae Fernández-Yépez and Knodus calliurus Ahl demonstrated the former is a junior synonym of Moenkhausia lepidura, whereas the latter should be removed from its synonymy. An identification key to the Moenkhausia lepidura-group is provided.

A new species of the catfish Neoplecostomus (Loricariidae: Neoplecostominae) from a coastal drainage in southeastern Brazil

A new species of loricariid catfish is described from the rio Perequê-Açú and surrounding basins, Parati, Rio de Janeiro State. The new species has the accessory process of ceratobranchial 1 more slender than the main body of the ceratobranchial, and a very large sesamoid ossification, markedly greater in size than the interhyal. Additionally, the new species presents a distinct dorsal color pattern consisting of a conspicuous horseshoe shaped light blotch with a central dark area posterior to the supraoccipital.(AU)

Uma espécie nova de loricarídeo é descrita do rio Perequê-Açú e bacias circundantes, Parati, Rio de Janeiro. A espécie nova apresenta o processo acessório do ceratobranquial 1 mais delgado do que o corpo principal do ceratobranquial, e uma ossificação sesamoide muito grande, marcadamente maior em tamanho do que o interhial. Adicionalmente, a espécie nova apresenta um padrão de colorido dorsal distinto que consiste em uma conspícua mancha clara em forma de casco de cavalo com uma área escura no centro posterior ao supraoccipital.(AU)

Redescription of Hisonotus notatus Eigenmann & Eigenmann, 1889 (Loricariidae: Hypoptopomatinae), the type species of the genus, and description of a new species from coastal drainages of southeastern Brazil

Our analyses showed that the type series of Hisonotus notatus , type species of the genus, is mixed, composed by two different species. Based on that, we redescribe H. notatus with the designation of a lectotype, restricting the species to rio São João drainage and other small coastal drainages running to the Baía de Guanabara and to the Baía de Sepetiba in Rio de Janeiro State. We also describe a new species of Hisonotus from drainages of the rio Paraíba do Sul, Lagoa Feia, rio Macaé, and coastal rivers of Espírito Santo State, from rio Itabapoana to rio Doce basin. These two species are sister-taxa and can be distinguished by the number of plates in the mid-dorsal series.

Nossas análises mostraram que a série-tipo de Hisonotus notatus , espécie-tipo do gênero, é mista, composta por duas diferentes espécies. Baseado nisso, nós redescrevemos H. notatus com a designação de um lectótipo, restringindo a espécie à drenagem do rio São João e outras pequenas drenagens que correm para a Baía de Guanabara e para a Baía de Sepetiba no estado do Rio de Janeiro. Também descrevemos uma nova espécie de Hisonotus das drenagens do rio Paraíba do Sul, Lagoa Feia, rio Macaé e rios costeiros do estado do Espírito Santo, do rio Itabapoana à bacia do rio Doce. Essas duas espécies são táxons irmãos e podem ser distinguidas pelo número de placas na série médio-dorsal.

A new Hasemania Ellis from the upper rio Paraná basin, with the redescription of Hasemania crenuchoides Zarske & Géry (Characiformes: Characidae)

A new Hasemaniaspecies is described from the headwaters of the rio Uberaba, rio Grande basin, State of Minas Gerais, Brazil. The new species is distinguished from its congeners by a combination of a black, vertically-elongate humeral spot, a single ossification in the position primitively occupied by infraorbitals four and five, four teeth on the inner series of premaxilla, and scales covering the anal-fin base. Hasemania crenuchoides is redescribed and its known geographic distribution is extended; it can be differentiated from other species of the genus by the combination of a black vertically-elongate humeral spot, ii,8 dorsal-fin rays, 11-14 branched anal-fin rays, the presence of separate infraorbitals four and five, and the presence of scales covering the anal-fin base. Phylogenetic relationships of H. crenuchoides and the new species within Hasemania are discussed.

Uma nova espécie de Hasemania é descrita para as cabeceiras do rio Uberaba, bacia do rio Grande, estado de Minas Gerais, Brasil. A nova espécie distingue-se de suas congêneres pela combinação de uma mancha umeral preta verticalmente alongada, uma ossificação única na posição primitivamente ocupada pelos infraorbitais quatro e cinco, quatro dentes na série interna do pré-maxilar e escamas cobrindo a base da nadadeira anal. Hasemania crenuchoides é redescrita e sua distribuição geográfica conhecida é ampliada; ela pode ser diferenciada das demais espécies do gênero pela combinação de uma mancha umeral preta verticalmente alongada, ii,8 raios na nadadeira dorsal, 11-14 raios ramificados na nadadeira anal, presença de infraorbitais quatro e cinco distintos e presença de escamas cobrindo a base da nadadeira anal. As relações filogenéticas de H. crenuchoides e da nova espécie são discutidas dentro de Hasemania.

The stream fish fauna from three regions of the Upper Paraná River basin / A ictiofauna de riachos de três regiões do alto rio Paraná

This study aimed to conduct an inventory of fish assemblages in small streams that are tributaries of large reservoirs in three previously unstudied regions of the Upper Paraná River basin. We sampled 117 streams from 1st to 3rd order in Araguari (Nova Ponte hydropower plant reservoir), Paranaíba (São Simão reservoir) and Grande (Volta Grande reservoir) drainages. In total, 20,696 specimens belonging to 100 species, 53 genera, 20 families and six orders were collected. Of these, 11,530 specimens and 41 species were recorded in Araguari, whereas 17 were exclusive to this drainage. In Grande drainage, 3,537 individuals belonging to 41 species (11 exclusive) and in Paranaíba, 5,629 specimens and 67 species (38 exclusive) were sampled. The mean richness per stream was 6.7 for Grande, 9.0 for Araguari and 10.9 for Paranaíba drainage. The predominant orders were Characiformes, 48% of the total richness, and Siluriformes, 36%. Three species were diagnosed as new: Astyanax sp. 1 (Grande and Paranaíba), Astyanax sp. 2 and Astyanax sp. 3 (both from Araguari), all from scabripinnis group. Another three were considered potentially new: Characidium sp. 1, Characidium sp. 2 and Rhamdiopsis sp. Among all records, eight species are not native from the Paraná basin: the exotics Oreochromis niloticus and Tilapia rendalli and the allochtonous Cyphocharax gillii, Hoplerythrinus unitaeniatus, Knodus moenkhausii, Poecilia reticulata, Roeboides descalvadensis and Trichomycterus brasiliensis. This study fills part of the existing knowledge gap about fish from small streams of the Paraná basin. Inventories of the fish fauna from these low-order water courses are important because they highlight their biodiversity relevance, including a significant number of unknown species. Thus, this study contributes to a better knowledge of the stream fish fauna of the upper Paraná River basin, as well as contribute to the establishment of strategies for conservation of this important component of aquatic biodiversity.

Este trabalho teve como objetivo realizar um inventário das assembleias de peixes em pequenos riachos afluentes de grandes reservatórios do alto rio Paraná, em três regiões até então desconhecidas pela literatura. Foram amostrados 117 riachos de 1a a 3a ordens nas bacias dos rios Araguari (na bacia de drenagem do reservatório de Nova Ponte), Paranaíba (reservatório de São Simão) e Grande (reservatório de Volta Grande). No total foram capturados 20.696 exemplares pertencentes a 100 espécies, seis ordens, 20 famílias e 53 gêneros. Destes, 11.530 exemplares e 41 espécies foram registradas na bacia do Araguari, sendo que 17 dessas espécies são exclusivas. Na bacia do rio Grande, foram registrados 3.537 exemplares pertencentes a 41 espécies (11 exclusivas) e na bacia do Paranaíba, foram registrados 5.629 exemplares e 67 espécies (38 exclusivas). A riqueza média por riacho foi de 6.7 para os riachos da bacia do rio Grande, 9.0 para os riachos da bacia do Araguari e 10.9 para os riachos da bacia do rio Paranaíba. As ordens predominantes foram Characiformes, com 48% da riqueza total e Siluriformes, com 36%. Três espécies pertencentes ao grupo scabripinnis foram diagnosticadas como novas: Astyanax sp. 1 (Grande e Paranaíba), Astyanax sp. 2 (Araguari) e Astyanax sp. 3 (Araguari). Outras três foram consideradas como potencialmente novas: Characidium sp. 1, Characidium sp. 2 e Rhamdiopsis sp. Entre todos os registros, oito espécies não são nativas da bacia do Paraná: as exóticas Oreochromis niloticus e Tilapia rendalli e as alóctones Cyphocharax gillii, Hoplerythrinus unitaeniatus, Knodus moenkhausii, Poecilia reticulata, Roeboides descalvadensise Trichomycterus brasiliensis. Este estudo preenche parte da lacuna de conhecimento existente sobre peixes de pequenos riachos da bacia do Paraná. Os inventários sobre a fauna de peixes em riachos de pequena ordem são importantes, pois evidenciam a ocorrência de grande diversidade, incluindo um número significativo de espécies ainda não descritas. Dessa forma, esse estudo contribui para um melhor conhecimento da fauna de peixes de riachos pertencentes è bacia do alto rio Paraná, além de colaborar para o estabelecimento de estratégias para conservação deste importante componente da biodiversidade aquática.

Microlepidogaster discus, a new species of Hypoptopomatinae (Siluriformes: Loricariidae) from the rio Jequitinhonha basin, southeastern Brazil.

A new Hypoptopomatinae is described from the upper rio Jequitinhonha basin. The new species is distinguished from all congeners by having the ventral laminar expansions of cleithrum and coracoid bearing only 1-30 odontodes, restricted to the area near the pectoral-fin insertion; the anterior plates of mid-ventral lateral series reduced, not ventrally elongated, the first or the second markedly round; pectoral-fin unbranched ray distinctly divided distally, with 7-15 ossified segments, reaching almost half of its length; and accessory process on first epibranchial present. Microlepidogaster discus is further distinguished from its congeners by several other osteological features. The problems concerning the taxonomy of Microlepidogaster, as well as the pattern of distribution of the genus, are discussed.