Description of Saccocoelioides miguelmontesi n. sp. (Digenea: Haploporidae) from characid fishes in the Iguazu River Basin based on morphological and molecular evidence.

Here we describe a new species of the genus Saccocoelioides found parasitizing Astyanax dissimilis Garavello & Sampaio, Psalidodon bifasciatus (Garavello and Sampaio) and Bryconamericus ikaa Casciotta, Almirón & Azpelicueta from the Iguazu National Park, Misiones province, Argentina. Saccocoelioides miguelmontesi n. sp. was studied based on morphological and molecular (28S rDNA and COI mtDNA sequences) data. The COI mtDNA tree indicated that the specimens collected from the three fish hosts are conspecific, with an intragroup p-distance of 0%. The new species shows an intermediate morphological configuration between the diminutive and robust forms described for Saccocoelioides by Curran (2018). Although, in the 28S rDNA tree, it is placed in a well-supported clade with the two robust species analysed (S. elongatus and S. magnus; p-distance of 1 and 2%, respectively), it differs from the robust group by the range of body size, mature egg size, oral and ventral sucker size, sucker ratio, oral sucker to pharynx ratio, and post-cecal or post-testis/body length percentage. Our results led us to redefine the robust group as having eggs shorter or equal in length to the pharynx. Saccocoelioides miguelmontesi n. sp. the 10th species reported from Argentina and the 7th species within the robust group.

Prosthenhystera gattii n. sp. (Digenea: Callodistomidae), a gallbladder parasite of Bryconamericus ikaa from the lower Iguazú River, described based on combined molecular and morphological evidence.

Adult forms of members of the Callodistomidae always parasitize the gallbladder of freshwater fishes and occur in Africa and America. This study provides a description of a new South American species belonging in Prosthenhystera from the gallbladder of a characid fish (Bryconamericus ikaa), and ribosomal gene sequences (28S rDNA and ITS1-5.8S-ITS2) are used to demonstrate molecular differences between the new species and congeners as well as explore interrelationships among congeners. Additionally, the first cytological analysis is conducted for a member of the family to determine chromosome number and arrangement. Prosthenhystera gattii n. sp. most closely resembles Prosthenhystera caballeroi in morphology, but the vitellarium is more extensive reaching anterior to the caecal bifurcation in the new species and the uterus is confined to the hindbody in P. gattii n. sp., whereas it extends to the level of the pharynx in P. caballeroi. Also, the testes, cirrus sac, seminal receptacle and the ratio of body length to width are larger in P. gattii n. sp. Independent Bayesian inference analyses of 28S rDNA and ITS1-5.8S-ITS2 sequence fragments produced phylograms that showed P. gattii n. sp. is more similar to Prosthenhystera obesa + Prosthenhystera oonastica than P. caballeroi + two unidentified species of Prosthenhystera, but with poor posterior probability support for the node in the ITS1-5.8S-ITS2-based phylogram. Further, the genetic distance between P. oonastica and P. gattii n. sp. are the largest among Prosthenhystera spp. Cytological analysis revealed ten metacentric chromosomes, which is fewer than the 12-18 chromosomes present in species from the closely related Gorgoderidae.

A new species of Knodus (Characiformes: Characidae: Stevardiinae) from the rio Aripuanã, rio Madeira basin, Brazil

A new species of the characid genus Knodus is described from the rio Aripuanã (rio Madeira basin). It can be distinguished from its congeners by its very low body depth, the presence of tri- to pentacuspid teeth on the outer premaxillary series, with the median cuspid larger than the lateral ones, the teeth of the inner premaxillary series pentacuspid, distinctly larger than those of the outer series, the maxillary teeth tri- to pentacuspid, with the median cusp slightly larger than the lateral ones, the four anteriormost dentary teeth pentacuspid, the smaller posterior teeth tri- to pentacuspid, a complete lateral line with 36-38 scales, 3 longitudinal scale series from pelvic fin origin to lateral line, and 11-12 circumpeduncular scales. The new species is also compared to incertae sedis species of 'Bryconamericus' from northern South America since phylogenetic studies suggest a closer relationship of those species with Knodus.(AU)

Uma nova espécie de um caracídeo do gênero Knodus é descrita do rio Aripuanã (bacia do rio Madeira). Esta espécie se distingue de suas congeneres por possuir o corpo muito estreito, a presença de dentes tri- a pentacúspides na série externa do pré-maxilar, com a cúspide mediana ligeiramente maior que as cúspides laterais, dentes da série interna pentacúspide, distintamente maiores que os da série externa, dentes do maxilar tri- a pentacúspides com a cúspode central discretamente maior que as laterais, os quatro dentes mais anteriores do dentário pentacuspidados, os dentes mais posteriores tricuspidados a pentacuspidados, a linha lateral complete com 36-38 escamas, 3 séries longitudinais de escamas entre a origem da nadadeira pélvica e a linha lateral, e 11-12 séries longitudinais de escamas circumpedunculares. A nova espécie é comparada com espécies incertae sedis de 'Bryconamericus' do norte da América do Sul uma vez que estudos filogenéticos sugerem a próxima relação daquelas espécies com Knodus.(AU)

A systematic review of Rhinopetitia Géry (Teleostei, Characiformes, Characidae) with descriptions of four new species and redescription of R. myersi Géry.

Rhinopetitia was known for a long time only by R. myersi, its type species, described from the Ilha do Bananal, Rio Araguaia basin, Tocantins, Brazil. Another recently described species, R. potamorhachia, was considered to differ from R. myersi by having the outer and inner rows of premaxillary teeth with seven to nine cusps, a midlateral dark stripe and a dark humeral blotch (versus outer and inner rows of premaxillary and of maxillary teeth with three to five cusps, and the absence of a dark midlateral stripe). Recently collected specimens from the Araguaia and Tocantins river basins are considered to belong to R. myersi, allowing to better characterize this species which is redescribed herein. Four new species are recognized for the genus, all from Brazil: 1) Rhinopetitia paucirastra, new species, collected from the upper Rio Tocantins drainage, state of Goiás, distinguished from all its congeners mainly by the presence of rudimentary and fewer gill rakers in external row on first gill arch; 2) R. oligolepis, new species originating from the Rio Jamanxim, Rio Tapajós drainage, state of Pará, differing from its congeners by having 4 longitudinal scale rows from dorsal-fin origin to lateral line; 3) R. melanohumeralis, new species, collected from small streams tributaries of the upper Rio Tapajós, and the upper Rio Xingu basins, states of Pará and Mato Grosso, that has the body as deep as in R. paucirastra but has well-developed and more gill rakers in the external row on first branchial arch; and 4) R. nigrofasciata, new species, collected in small tributaries of the upper portions of the Rio Tapajós and Rio Xingu basins, states of Pará and Mato Grosso, with the body narrower than in R. paucirastra and R. melanohumeralis.

Water quality parameters, biomarkers and metal bioaccumulation in native fish captured in the Ilha River, southern Brazil.

The Ilha River is one of the main tributaries of the Sinos River, southern Brazil, and it is located in an area characterized by low population density and presence of agricultural activities. Thus, this study aimed to assess the water quality of two sites of the Ilha River (source and mouth, S1 and S2 respectively) in five sampling periods using water physicochemical and microbiological analyses, biomarkers, such as condition factor, micronucleus test, gill histopathological analysis, and metal bioaccumulation in the native fish Bryconamericus iheringii. Mean values of BOD5, thermotolerant coliforms, aluminum, iron and lead exceeded the limits established by the Brazilian legislation for surface waters at both sampling sites. Significant higher micronucleus, nuclear abnormalities and mucous cells frequencies were found at S2 in, at least, one sampling period, whereas fish from S1 presented significant lower condition factor, higher frequencies of lamellar alterations and higher concentrations of chromium and nickel in muscle. Additionally, concentrations of cadmium, chromium and lead in fish muscle exceeded the limits considered safe for human consumption at both sites in at least one sampling period. Data from our study evidenced the mouth of the Ilha River suffers from point genotoxic effects, whereas the source is also contaminated by metals, despite being located in an area under minor anthropic activities.

Molecular variants in populations of Bryconamericus aff. iheringii (Characiformes, Characidae) in the upper Paraná river basin / Variantes moleculares em populações de Bryconamericus aff. iheringii (Characiformes, Characidae) da bacia do alto rio Paraná

There are evidences that Bryconamericus aff. iheringii represents a species complex. DNA molecular markers have been effective in studies on phylogeny, taxonomy, and identification of cryptic species. In this study, partial sequences of genes of ATPase 6 and 8 were used to assess genetic diversity within and among populations of B. aff. iheringii of sub-basins of Tibagi, Pirapó and Ivaí rivers, belonging to the Upper Paraná river basin. The analysis of the sequences of genes pointed out high genetic diversity in B. aff. iheringii from the sub-basins studied with genetic distance values comparable to those found among different species. There was a division of the individuals into five groups. The comparison with other species of Bryconamericus that have sequences available in GenBank confirmed that the individuals studied have relevant values of genetic distance, found among different species. Nevertheless, with the available data it is not possible to refute the hypothesis that the populations correspond to a group resulting from hybridization or that there might have been introgression of mitochondrial DNA among different species.

Há indícios de que Bryconamericus aff. iheringii represente um complexo de espécies. Os marcadores moleculares de DNA têm sido eficazes em estudos de filogenia, taxonomia e identificação de espécies crípticas. Neste estudo, as seqüências parciais de genes da ATPase 6 e 8 foram utilizados para avaliar a diversidade genética dentro e entre populações de B. aff. iheringii das sub-bacias dos rios Tibagi, Pirapó e Ivaí, pertencentes a bacia do Alto Rio Paraná. As análises das seqüências dos genes apresentaram alta diversidade genética em B. aff. iheringii das sub-bacias estudadas, com valores de distâncias genéticas semelhantes às encontradas entre espécies diferentes. Houve uma divisão dos indivíduos em cinco grupos. A comparação com outras espécies de Bryconamericus que têm seqüências disponíveis no GenBank confirmou que os indivíduos estudados possuem valores relevantes de distância genética encontrados entre espécies diferentes. No entanto, com os dados disponíveis não é possível descartar a hipótese de que as populações correspondem a um grupo resultante de hibridação, nem que houve introgressão de DNA mitocondrial entre espécies diferentes.

Temporal distribution of ichthyoplankton in the Ivinhema River (Mato Grosso do Sul State/ Brazil): influence of environmental variables

Information on ichthyoplankton is an important tool in determining reproduction periods that - if associated to environmental variables - allows for inferences about the factors that regulate their intensity, beginning, and ending. In this context, this study aims to establish (i) ichthyoplankton composition; (ii) temporal variations in the overall density of eggs and larvae and among the most important taxa; and (iii) the influence of some abiotic and biotic variables on these organisms' abundance. Ichthyoplankton sampling was undertaken during the period between April 2005 and March 2006 at the Ivinhema River, upper Paraná River basin (MS/Brazil). Differences in the ichthyoplankton's temporal variation were evaluated using unifactorial ANOVAs. Principal Component Analysis and Pearson's correlation were used for the relationships between eggs and larvae densities and environmental variables. A total of 3,341 eggs and 2,896 larvae were captured during the period studied, and most of them were medium-sized and large species that carried out some type of reproductive migration. The highest densities of eggs and larvae occurred during the months of spring and summer, except for those of Bryconamericus stramineus, which was most abundant during the winter. The density of ichthyoplankton was most positively correlated with the water's outflow and temperature. However, Plagioscion squamosissimus was positively related to the increase in pH and in zooplanktonic organisms, while B. stramineus was inversely correlated with water outflow and temperature. The study concludes that spawning is most intense in the spring and summer, especially between November and January, and is related to the greatest values of water temperature and outflow. Nevertheless, the response and reproductive intensity in relation to the environmental variables vary according to the species.

As informações sobre o ictioplâncton são ferramentas importantes para a determinação do período de reprodução que, se associado às variáveis ambientais, permitem inferências sobre os fatores que regulam sua intensidade, início e término. Nesse contexto, o presente estudo visa determinar: (i) a composição do ictioplâncton; (ii) as variações temporais na densidade de ovos, larvas e dos táxons mais importantes; e (iii) a influência de algumas variáveis abióticas e bióticas sobre a abundância destes organismos. As coletas de ictioplâncton foram realizadas no período de abril de 2005 a março de 2006, no rio Ivinhema, bacia do alto rio Paraná (MS/Brasil). Diferenças nas variações temporais do ictioplâncton foram avaliadas por ANOVAs unifatoriais. Análises de Componentes Principais e correlação de Pearson foram utilizadas para avaliar as relações entre densidade de ovos e larvas e as variáveis ambientais. Durante o período estudado, foram capturados 3.341 ovos e 2.896 larvas, sendo que a maior parte foi de espécies de médio e grande porte e que realizam algum tipo de migração reprodutiva. Ovos e larvas apresentaram suas maiores densidades nos meses de primavera e verão, exceto Bryconamericus stramineus que foi mais abundante no inverno. A densidade de ictioplâncton esteve mais correlacionada positivamente com a vazão e a temperatura da água. Contudo, Plagioscion squamosissimus apresentou relação positiva com o aumento do pH e dos organismos zooplanctônicos, enquanto B. stramineus apresentou correlação inversa com a vazão e temperatura da água. Conclui-se que as desovas são mais intensas na primavera-verão, principalmente entre novembro e janeiro, e estão relacionadas aos maiores valores de temperatura e vazão da água. Entretanto, a resposta e a intensidade reprodutiva às variáveis ambientais variam de acordo a espécie.

A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species

The species of Hemibrycon occurring in the east of the Andean Cordilleras are reviewed based on their type series and additional specimens. Nine species are redescribed: H. beni from río Beni basin, Bolivia; H. helleri from the upper rio Ucayali, Peru; H. huambonicus from the ríos Huallaga and Marañon basins, Peru; H. jeslkii from the upper portions of ríos Marañon, Ucayali and Madeira basins, Bolivia, Brazil, and Peru; H. metae from río Orinoco basin, Colombia and Venezuela, and Caribbean coastal basins of Venezuela; H. polyodon (type species) from río Pastaza basin, Ecuador; H. surinamensis from coastal basins of French Guiana and Suriname, and from lower rios Tapajós, Tocantins and Xingu basins, Brazil; H. taeniurus from river basins from Trinidad Island, Trinidad and Tobago, and H. tridens from upper río Ucayali basin, Peru. Two new species are described: H. inambari from the upper río Madre de Dios basin, Peru and H. mikrostiktos from río Ucayali basin, Peru. These species are distinguished among themselves mainly by the color pattern, and meristic characters. The distribution area of the genus is enlarged reaching the lower Tapajós, Tocantins and Xingu river basins, Brazil, with the first record of the occurrence of H. surinamensis in this country. A new description and diagnosis is provided for the type species of the genus, regardless its recent redescription. The type series of H. helleri that was previously considered dubious is found and described. Hemibrycon coxeyi and H. pautensis are considered junior synonyms of H. polyodon. Tetragonopterus (Hemibrycon) trinitatis, previously considered species inquirenda in Characidae, and Hemibrycon guppyi are junior synonyms of H. taeniurus. Hemibrycon orcesi is transferred to Boehlkea. A taxonomic key for the species of the genus to the east of the Andean Cordilleras is presented.

As espécies de Hemibrycon que ocorrem a leste das Cordilheiras dos Andes são revisadas com base na análise do material tipo e exemplares adicionais. Nove espécies são redescritas: H. beni da bacia do río Beni, Bolívia; H. helleri do alto río Ucayali, Peru; H. huambonicus para as bacias dos ríos Huallaga e Marañon, Peru; H. jeslkii para as porções superiores das bacias dos rios Marañon, Ucayali e Madeira, Bolívia, Brasil e Peru; H. metae para a bacia do río Orinoco, Colômbia e Venezuela, e bacias costeiras do Caribe na Venezuela; H. polyodon (espécie-tipo) para a bacia do río Pastaza, Equador; H. surinamensis para as bacia costeiras da Guiana Francesa e Suriname, e porção inferior das bacias dos rios Tapajós, Tocantins e Xingu, Brasil; H. taeniurus para os rios da ilha de Trinidad, Trinidad and Tobago; H. tridens para a bacia do alto río Ucayali, Peru. Duas espécies novas são descritas: H. inambari para a bacia do alto río Madre de Dios, Peru e H. mikrostiktos para a bacia do río Ucayali, Peru. Estas espécies distinguem-se principalmente pelo padrão de colorido e caracteres merísticos. A área de distribuição do gênero é ampliada para as porções inferiores das bacias do Tapajós, Tocantins e Xingu, Brasil, com o primeiro registro de H. surinamensis para este país. Uma nova diagnose e descrição são fornecidas para a espécie-tipo do gênero, apesar de ter sido recentemente redescrita. A série-tipo de H. helleri previamente considerada questionável é encontrada e descrita. Hemibrycon coxeyi e H. pautensis são considerados sinônimos juniores de H. polyodon. Tetragonopterus (Hemibrycon) trinitatis, anteriormente considerada como species inquirenda em Characidae, e Hemibrycon guppyi são sinônimos juniores de H. taeniurus. Hemibrycon orcesi é transferida para Boehlkea. É apresentada uma chave taxonômica para as espécies do gênero a leste das Cordilheiras dos Andes.

Food resource used by small-sized fish in macrophyte patches in ponds of the upper Paraná river floodplain - DOI: 10.4025/actascibiolsci.v31i2.3266

This study analyzed the diet of seven small-sized fish species (Characidae) and assessed their use of food resources. The species were collected in 2001 from nine ponds with aquatic macrophytes in the Paraná river floodplain, Brazil. Astyanax altiparanae, Astyanax fasciatus, Hemigrammus marginatus and Moenkhausia intermédia consumed aquatic and terrestrial insects. Bryconomericus stramineus and Moenkhausia sanctaefilomenae co-dominantly ate insects and microcrustaceans, whereas Hyphessobrycon eques had microcrustaceans as their most important food resource. Overlapping feeding coefficients varied from intermediate (0.4-0.6) to low ( 0.4) for the majority of the combination pairs. A high mean intestinal length was verified for A. altiparanae and A. fasciatus, while a smaller mean was found for H. eques. When comparing all these results, it is possible to conclude that the species were partially segregated by the trophic niche dimension. Thus, the co-existence and higher abundance of these small fish in the shoreline of the ponds is explained by high feeding adaptability, absence of specializations in the feeding tract (except intestinal length) and the wide food supply provided by aquatic macrophytes.

Una nueva especie de pez del género Bryconamericus (Ostariophysi: Characidae) del río Magdalena, con una clave para las especies de Colombia

A new species of fish of the genus Bryconamericus (Ostariophysi: Characidae) from the Magdalena river, with a key to Colombian species. Based on a series of 90 specimens, and using morphometric, meristic and osteological characters, a new species of the genus Bryconamericus is described from Pontesuela Creek at the mouth of Coclina Creek in the middle Magdalena river Basin of Colombia. We use box graphs with 99% confidence intervals to illustrate the extent of meristic character overlap and to help distinguish this new taxon from other species of the Magdalena River. The species can be distinguished from all congeners by the combination of the following characters: the higher number of lateral line scales (50-54 vs. 30-50, except B. terrabensis with 47-54); more scales between the lateral line and the dorsal fin origin (9-11 vs. 4-9); more scales between the lateral line and the pelvic fin origin (8-10 vs. 2-8); more scales between lateral line and anal fin origin (8-10 vs. 2-8, except B. terrabensis with 6-9) and more predorsal scales (16-18 vs. 9-16, except B. huilae with 14-19 scales, B. galvisi with 12-17 and B. tolimae with 13-17). Rev. Biol. Trop. 56 (4): 1749-1763. Epub 2008 December 12.

Con base en una serie de 90 ejemplares, en caracteres morfométricos, merísticos y osteología, se describe una nueva especie de Bryconamericus de la Quebrada La Pontesuela, boca de la quebrada Coclina, cuenca media del río Magdalena en Colombia. Se utiliza un gráfico de cajas con intervalos de confianza al 99% para ilustrar la medida merística que mostrara menor solapamiento y distinguiera parcialmente al nuevo taxon de las otras especies del río Magdalena. La especie se distingue de sus congéneres por el mayor número de escamas: sobre la línea lateral (50-54 vs. 30-50, excepto B. terrabensis con 47-54 escamas), entre la línea lateral y el origen de la aleta dorsal (9-11 vs. 4-9), entre la línea lateral y el origen de las aletas pélvicas (8-10 vs. 2-8), entre la línea lateral y el origen de la aleta anal (8-10 vs. 2-8 excepto B. terrabensis con 6-9) y predorsales (16-18 vs. 9-16, excepto B. huilae con 14-19 escamas, B. galvisi con 12 a 17 y B. tolimae con 13-17).

Chromosome divergence and NOR polymorphism in Bryconamericus aff. iheringii (Teleostei, Characidae) in the hydrographic systems of the Paranapanema and Ivaí Rivers, Paraná, Brazil

Cytogenetic studies were carried out in three populations of Bryconamericus aff. iheringii from two hydrographic systems of the Paranapanema and Ivaí Rivers, separated by a watershed, both belonging to the upper Paraná River basin. Specimens had a constant diploid number 2n = 52 chromosomes. However, three karyotype formulae were identified in the three populations: B. aff. iheringii from the Maringá stream had 12M+18SM+8ST+14A (FN = 90); specimens from Keller River showed 8M+28SM+6ST+10A (FN = 94) and specimens from the Tatupeba stream had 8M+20SM+8ST+16A (FN = 88). Nucleolar organizer regions (NORs) were identified by silver nitrate staining and fluorescent in situ hybridization (FISH) with an 18S rDNA probe. Specimens from Tatupeba stream had a simple NOR system located in a terminal position of the short arm of a pair of large submetacentric chromosomes. Ag-NOR and FISH methodologies revealed multiple NORs in specimens of the Maringá stream and Keller River. Differences in chromosome structure and in NOR patterns in the three populations of B. aff. iheringii revealed fixed evolutionary chromosome divergence. Aspects related to karyotypic variations and to geographic isolation of these populations are discussed.

Reproductive biology of Bryconamericus stramineus Eigenmann, 1908 (Ostariophysi: Characidae) from the Rio Ibicuí, RS, Brazil

Reproduction of Bryconamericus stramineus was described based on the analysis of 208 females and 166 males collected monthly in the Rio Ibicuí, from April 2001 through March 2002. Reproduction occurred between September and December, with a lower peak in February. The mean absolute fecundity was 371.3 (± 244.6) oocytes and the mean relative fecundity was 0.35 (± 0.08) oocytes/mg of total weight and the fish was a multiple spawner. A weak correlation between GSI of males and day length was observed. Other parameters (stomach repletion and hepatosomatic index, rainfall and temperature) did not show any correlation with GSI. However, some of these factors might act as "starters" of gonadal maturation. The presence and frequency of fin ray hooks on the males was compared with the gonadal maturation stages, months and standard length classes. Well-developed hooks were found mainly in the mature males during the reproductive period and in the largest individuals.

A reprodução de Bryconamericus stramineus é descrita baseada na análise de 208 fêmeas e 166 machos coletados mensalmente no rio Ibicuí, RS, de abril/2001 a março/2002. A reprodução ocorreu entre setembro e dezembro, com um pico menor em fevereiro. A fecundidade absoluta média é de 371.3 (± 244.6) ovócitos e a fecundidade relativa média é de 0.35 (± 0.08) ovócitos/mg de peso total e a espécie tem desova parcelada. Foi observada uma fraca correlação entre IGS de machos e fotoperíodo; os índices de repleção estomacal e hepatossomático, a pluviosidade e temperatura não mostraram nenhuma correlação. Porém, sugerimos que alguns destes fatores possam agir como "desencadeadores" da maturação gonadal. A presença e freqüência de ganchos nas nadadeiras de machos foi comparada com as fases de maturação gonadal, meses e classes de comprimento padrão. Ganchos bem-desenvolvidos foram encontrados principalmente em machos maduros, durante o período reprodutivo e nos indivíduos maiores.