Chromosomal Diversification in Pseudacanthicus Species (Loricariidae, Hypostominae) Revealed by Comparative Mapping of Repetitive Sequences.

Pseudacanthicus is a genus of Neotropical fish with eight valid species, in addition to numerous lineages not formally identified. It occurs along the Amazon and Tocantins River basins, in Suriname and in the Guiana shield. There are no karyotypic data in the literature for species of this genus. Here, the karyotypes of three Pseudacanthicus species (P. spinosus, P. leopardus and Pseudacanthicus sp.) were comparatively analyzed by classical cytogenetics and fluorescence in situ hybridization using 18S and 5S rDNA probes, U2 snDNA and telomeric sequences. The analyzed species presented 52 chromosomes and KF = 18 m + 34 sm. Constitutive heterochromatin occurred in blocks on a few chromosomes. The 18S rDNA occurred in a single pair; interestingly, P. leopardus presented only one locus of this sequence in its diploid genome. The 5S rDNA sequence occurred in only one pair in P. leopardus, and in multiple sites in Pseudacanthicus sp. and P. spinosus. The snDNA U2 occurred in only one pair in all analyzed species. Telomeric sequences did not show interstitial sites. Although Pseudacanthicus species share the same 2n and KF, repetitive sequence analysis revealed karyotypic diversity among these species. The occurrence of DNA double-strand breaks related to fragile sites, unequal crossing over and transpositions is proposed as the mechanism of karyotypic diversification, suggesting that the conservation of the karyotypic macrostructure is only apparent in this group of fish.

New species of glass knifefish genus Eigenmannia (Gymnotiformes: Sternopygidae) with comments on the morphology and function of the enlarged cephalic lateral-line canals of Sternopygidae.

A new species of Eigenmannia is described from the Rio Paraná (the Grande, Paranapanema and Tietê basins). This new species is distinguished from all congeners by colouration pattern, position of the mouth, relative depth of posterodorsal expansion on infraorbitals 1 + 2, number of teeth, osteological features, number of rows of scales above lateral line (LL) and morphometric data. Comments on the widened cephalic lateral-line canals of Sternopygidae and a dichotomous key to the species of Eigenmannia from the Rio Paraná Basin are provided.

Bunocephalus hertzi, a new banjo catfish from the upper Rio Paraná basin, Brazil (Siluriformes: Aspredinidae), with the redescription of Bunocephalus larai Ihering, 1930.

Bunocephalus hertzi, new species, is described from two tributaries of the upper Rio Paraná basin. Because the type series of B. larai (the only other species of Bunocephalus in the basin) is lost, a redescription of B. larai is also provided herein. Bunocephalus larai and B. hertzi can be distinguished from all its congeners, except B. minerim, by the absence of an epiphyseal bar (vs. present). From B. minerim, both species can be distinguished by the presence of 10 principal caudal-fin rays (vs. 9). Bunocephalus hertzi can be differentiated from B. larai by the longer coracoid process size (11.9-16.2% vs. 6.7-9.8% SL), shorter maxillary barbel (just reaching the pectoral fin origin; 54.6-67.4% vs. 73.7-84.6% HL) and skull ornamentation represented by five bony protuberances between the posterior end of the occipital and the origin of the dorsal fin (vs. four bony protuberances).

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.

Description of a new Pimelodella (Siluriformes: Heptapteridae) species with a discussion on the upper pectoral girdle homology of Siluriformes.

A new species of Pimelodella is described from several right-bank tributaries of the Rio Madeira basin in Amazonas and Rondônia states, Brazil. The new species differs from all congeners by the supraoccipital process not reaching the anterior nuchal plate, 43-45 total vertebrae, maxillary barbels reaching between adpressed anal-fin terminus and caudal-fin origin, epiphyseal branch of supraorbital laterosensory canal emerging as two distantly-positioned pores and a conspicuous black mark at distal third of dorsal fin, between dorsal-fin spine and third branched ray. A detailed description of the cephalic laterosensory system of the new species is provided and contrasted with other Siluriformes and Ostariophysi. A discussion regarding homology of the catfish upper pectoral girdle bones is offered in light of modifications of the postotic and supratemporal lateral-line canals. Based on the placement of the pterotic branch of the postotic canal, it is concluded that the extrascapula is fused to the pterotic in Siluriformes. Results presented herein offer an example of how lateral-line morphology can be used as a compelling source of evidence to help determine homology of cranial and upper pectoral girdle bones.

A new sexually dichromatic miniature Hyphessobrycon (Teleostei: Characiformes: Characidae) from the Rio Formiga, upper Rio Juruena basin, Mato Grosso, Brazil, with a review of sexual dichromatism in Characiformes.

Hyphessobrycon myrmex sp. nov., is described from the Rio Formiga, upper Rio Juruena, upper Rio Tapajós basin, Mato Grosso, Brazil. The new species can be distinguished from congeners by having the lower half of the body deeply pigmented with dark chromatophores, chromatophores concentrated above the anal fin and forming a broad, diffuse, dark midlateral stripe and by having a dense concentration of dark chromatophores along unbranched dorsal-fin rays and distal portions of the two or three subsequent branched rays. In life, H. myrmex exhibits a conspicuous sexual dichromatism, with adult males red to orange and females and immatures pale yellow. A list containing 108 sexually dichromatic taxa in six families of Characiformes is provided and the distribution of this poorly known type of dimorphism across the Characiformes is discussed.

Influence of an artificial dam on the fish assemblage of a Neotropical stream / Influência de um reservatório artificial na assembleia de peixes de um riacho Neotropical

The objective of this study was to evaluate the influence of a dam on the ecological parameters of the fish assemblages of a stream of second order of the upper Paraná River basin, southern Brazil. Samplings of abiotic data and ichthyofauna occurred quarterly between September 2012 and June 2013. Were collected 3,128 individuals in six orders, eight families and 13 species. The Cluster analysis (Jaccard) based on species composition indicated the separation of the sampling units into two groups, demonstrating the dissimilarity between upstream and downstream units. The artificial dam was characterized as a discontinuity factor for diversity patterns and ecological processes related to biota. Thus, this study has indications that the creation of dams can significantly affect the richness and abundance of fish species of small lotic systems, as streams, by modifying their environments.

O objetivo do presente estudo foi avaliar a influência de uma barragem sobre os parâmetros ecológicos das assembleias de peixes presentes em um riacho de segunda ordem da bacia do Alto rio Paraná, sul do Brasil. As amostragens dos dados abióticos e da ictiofauna ocorreram trimestralmente entre o período de setembro de 2012 e junho de 2013. Foram coletados 3.128 indivíduos distribuídos em seis ordens, oito famílias e 13 espécies. A análise de agrupamento com base no índice de Jaccard indicou a separação dos pontos em dois grupos com relação à composição de espécies, demonstrando distinção entre os pontos à montante e à jusante da barragem artificial. A barragem artificial se caracterizou como um fator de descontinuidade para os padrões de diversidade e para os processos ecológicos relacionados à biota. Sendo assim, o presente trabalho possui indicativos de que a criação de barragens, mesmo que para a formação de pequenas represas ou açudes, pode afetar de forma significativa a riqueza e abundância das espécies de peixes de pequenos sistemas lóticos, como riachos, por meio da modificação de seus ambientes.

Diet and ecomorphology of Leporinus reticulatus (Characiformes: Anostomidae) from the upper Rio Juruena, MT, Brazil: ontogenetic shifts related to the feeding ecology / Dieta e ecomorfologia de Leporinus reticulatus (Characiformes: Anostomidae) do alto Rio Juruena, MT, Brasil: alterações ontogenéticas relacionadas à ecologia alimentar

The conservation of diverse and well-distributed fish taxa, as the genus Leporinus, relies intrinsically on the knowledge of the ecological attributes of its representatives. Aiming to increase this knowledge, studies on diet and ecomorphology are ideal to provide important information about species ecology. Thus, this study aimed to analyze aspects of feeding ecology of L. reticulatus, from the upper Rio Juruena, Mato Grosso State, Brazil. The diet of specimens in different ontogenetic stages was compared, as well as their teeth morphology and ecomorphological attributes. Leporinus reticulatus presented omnivorous diet, with higher consumption of invertebrates by smaller specimens (younger ones), and gradual introduction of plant items in larger specimens (older ones). The items consumed by the individuals and the ecomorphological attributes indicated that the species is generalist and opportunistic, besides its association with the river bottom, evidencing a benthic feeding behavior. This species presents a gradual ontogenetic modification in teeth shape and mouth positioning, ranging from a terminal mouth with tricuspid teeth, in smaller specimens, to an inferior mouth with spatula shaped teeth with no cusps, in larger specimens.The ecomorphological attributes indicate an increasing swimming efficiency, and ability for performing vertical displacements, along the ontogenetic development, which in addition to the morphological ontogenetic alterations in the buccal apparatus, contributes to a better ability to explore another niches.

A conservação de táxons de peixes de grande diversidade e amplamente distribuídos, como o gênero Leporinus, depende intrinsicamente do conhecimento de atributos ecológicos de seus representantes. Objetivando o aumento deste conhecimento, estudos que abordam a dieta e a ecomorfologia são ideais para prover informações importantes sobre a ecologia de espécies. Assim, este trabalho teve como objetivo analisar aspectos da ecologia alimentar de L. reticulatus originários do alto Rio Juruena, estado do Mato Grosso, Brasil. Foi comparada a dieta de espécimes em diferentes estágios ontogenéticos, assim como a morfologia dos dentes e atributos ecomorfológicos. Leporinus reticulatus apresentou dieta onívora, com maior consumo de invertebrados pelos espécimes de menor porte (mais jovens), e introdução gradual de itens vegetais por espécimes de maior porte (mais velhos). Os itens consumidos pelos indivíduos e os atributos ecomorfológicos indicaram que esta espécie é generalista e oportunista, além de sua associação com o fundo do rio, evidenciando um comportamento alimentar bentônico. Esta espécie apresenta modificação ontogenética gradual no formato dos dentes e posição da boca, variando de uma boca terminal e dentes tricúspides, em espécimes menores, a uma boca inferior e dentes em forma de espátula sem cúspides, em espécimes maiores. Os atributos ecomorfológicos indicaram um crescente aumento na eficiência natatória, e na habilidade de realizar deslocamentos verticais, ao longo do desenvolvimento ontogenético, o que, em conjunto às alterações morfológicas ontogenéticas no aparato bucal, contribuem para uma melhor habilidade em explorar outros nichos.

Occurrence of intersexuality in "Lambaris", Astyanax scabripinnis (Jenyns, 1842), small characids from the Brazilian streams

During studies carried out with a small characid (Astyanax scabripinnis), from the Brazilian streams located in Cerrado biome, some gonads of fishes exhibited sparse oocytes in perinucleolar stage embedded in normally developing testicular tissues. Another pattern of gonad intersex with vitellogenic oocytes and mature lobules was observed in the gonads of fishes collected from a reservoir supplied by the Atlantic Forest stream. These gonads in different stages of maturation were examined histologically. The results revealed the patterns occurring in fishes of the same species, from four different populations.

Durante estudos efetuados com pequenos caracídeos (Astyanax scabripinnis) de riachos do Cerrado brasileiro, localizados nos Estados de Minas Gerais e de São Paulo, foram encontrados alguns peixes com gônadas exibindo oócitos em estágio perinucleolar dispersos, embebidos em tecidos testiculares em desenvolvimento. Em exemplares da mesma espécie, provenientes de um riacho situado na Mata Atlântica do Estado de São Paulo, outro padrão de gônadas intersexuadas foi registrado, mostrando oócitos vitelogênicos e lóbulos maduros presentes na mesma gônada. As gônadas em diferentes estágios de maturação foram submetidas a análises histológicas. Os resultados obtidos mostram os padrões morfológicos e as freqüências de ocorrência dos intersexos encontrados em peixes do " complexo" A. scabripinnis provenientes de quatro diferentes populações. São discutidas as prováveis causas ambientais responsáveis por estas alterações.