Rapid assessment of the ichthyofauna of the southern Guiana Shield tributaries of the Amazonas River in Pará, Brazil

The Northern Pará Drainage System encompasses the left-bank tributaries of the Amazonas River in the southern Guiana Shield region of Pará state, Brazil. Five of the region's state protected areas are considered strategic for the conservation of its biodiversity. In the present study, we assessed the ichthyofauna of the five state protected areas of the Northern Pará Drainage System. Seven expeditions were conducted between January 2008 and January 2009, which surveyed stretches of the Cuminá, Cuminapanema, Curuá, Jari, Mapuera, Nhamundá, and Paru rivers. These surveys yielded 286 species belonging to 38 families and eight orders, including seven new records of fish species for Brazil, six of which are also new records for the Amazon basin. Our results provide a valuable database for future research and conservation programs in the protected areas of the region. (AU)

A new species of Pseudobunocephalus Friel, 2008 (Siluriformes: Aspredinidae) from the lower Tocantins and Mearim river drainages, North and Northeast of Brazil.

Pseudobunocephalus timbira, new species, is described from streams of the lower Tocantins and the Mearim river drainages, in North and Northeast of Brazil. Pseudobunocephalus timbira can be distinguished from all congeners by having the second hypobranchial and the third basibranchial cartilaginous (vs. ossified). Additionally, it can be dintinguished from P. lundbergi by the following putative apomorphic features within Pseudobunocephalus: posterolateral process of premaxilla present (vs. absent); bony knobs in dorsal lamina of Weberian apparatus absent (vs. present); distal end of posterior margin of 5th parapophysis not enlarged (vs. enlarged); number of ribs three (vs. four or five) and infraorbital sensory canal entering neurocranium via frontal (vs. via sphenotic). It is distinguished from P. bifidus and P. iheringii by having a gracile body not surpassing 34 mm SL (vs. robust body, reaching up to 59 mm SL, respectively); by having the posterior margin of cranial fontanel concave (vs. posterior margin somewhat straight with parieto-supraoccipital extending anteriorly); by having a conspicuous knobby ornamentation on dorsal surface of skull (vs. skull knobs slightly pronounced); by having Weberian ventral blade of hemal canal opened (vs. closed) and by the absence of serrations on the proximal portion of the anterior margin of pectoral-fin spine (vs. serrations covering entire anterior margin of the pectoral spine). Additionally, it can be distinguished from P. amazonicus, P. rugosus and P. quadriradiatus, by having the posterolateral mental barbel with at least one fleshy lobe located proximally along the posterior margin (vs. posterolateral mental barbel simple, not having fleshy lobes). It also differs from P. amazonicus and P. rugosus by having five branchiostegal rays (vs. four). It also can be distinguished from P. amazonicus by having the contact of hyomandibula cartilage with neurocranium limited to the sphenotic (vs. extending to both sphenotic and pterotic); by having the ventral blade of Weberian apparatus open (vs. closed) and by anterior exit of hemal canal in abdominal vertebra (vs. in complex vertebra); from P. rugosus by coloration of proximal portion of caudal fin similar to rest of caudal fin (vs. clear patch) and from P. quadriradiatus by the total number of pectoral fin-rays six (vs. five). Variable characteristics within Pseudobunocephalus species are summarized and comments on the phylogenetic relationships and the disjunct distribution of the new species are made. [Species zoobank url: urn:lsid:zoobank.org:act:392F95E0-86E1-4386-8779-C4F71098DBCC].

Unexpected species diversity in electric eels with a description of the strongest living bioelectricity generator.

Is there only one electric eel species? For two and a half centuries since its description by Linnaeus, Electrophorus electricus has captivated humankind by its capacity to generate strong electric discharges. Despite the importance of Electrophorus in multiple fields of science, the possibility of additional species-level diversity in the genus, which could also reveal a hidden variety of substances and bioelectrogenic functions, has hitherto not been explored. Here, based on overwhelming patterns of genetic, morphological, and ecological data, we reject the hypothesis of a single species broadly distributed throughout Greater Amazonia. Our analyses readily identify three major lineages that diverged during the Miocene and Pliocene-two of which warrant recognition as new species. For one of the new species, we recorded a discharge of 860 V, well above 650 V previously cited for Electrophorus, making it the strongest living bioelectricity generator.

Eigenmannia besouro, a new species of the Eigenmannia trilineata species-group (Gymnotiformes: Sternopygidae) from the rio São Francisco basin, northeastern Brazil.

A new species of the Eigenmannia trilineata species-group is described from the rio São Francisco basin, Brazil. It is distinguished from closely related species by a unique set of characters, including a subterminal mouth, the presence of ii,13-14 pectoral-fin rays, a coronomeckelian bone that is 30% the length of Meckel's cartilage, the specific pattern of the dentition of the premaxilla and dentary, and the more anterior origin of the superior midlateral stripe. Comments on species of the E. trilineata species-group are presented.

A new species of Aspidoras Ihering (Siluriformes: Callichthyidae: Corydoradinae) from the Rio Xingu Basin, Pará, Brazil.

A new species of Aspidoras is described from an unnamed stream in the Rio Xingu Basin, Castelo de Sonhos municipality, Pará State, representing the northernmost record of the genus along the edge of the Brazilian Shield in the Amazon Basin. Aspidoras marianae is easily distinguished from all congeners in having minute odontode-bearing platelets scattered over the surface of the snout region, minute platelets between the parieto-supraoccipital process and the nuchal plate, and other shared features related to color pattern, morphometrics, meristics and morphological data. Comments about exclusive and shared features are presented.

Karyotypic and morphological divergence between two cryptic species of Eigenmannia in the Amazon basin with a new occurrence of XX/XY sex chromosomes (Gymnotiformes: Sternopygidae)

Eigenmannia species are widely distributed in the Neotropics, with eight valid species currently recognized. Populations of Eigenmannia from three locations in the eastern Amazon were investigated using cytogenetic and morphological techniques, revealing two taxa designated here as Eigenmannia sp. "A" and Eigenmannia sp. "B". The species differ in three morphometric characters, two meristic characters, and one osteological character. Eigenmannia sp. "A" presents 2n = 34 (22 m/sm+12 st/a) and Eigenmannia sp. "B" presents 2n = 38 (14 m/sm+24st/a) and simple differentiated sex chromosomes of the type XX/XY. In both species the Constitutive Heterochromatin (CH) rich in A-T bases is distributed in the centromeric region of all chromosomes. Eigenmannia sp. "B" also presents CH blocks in the interstitial region of chromosome pairs 8, 9 and X which are positively stained with CMA3, indicating G-C rich regions. The NOR is located on the short arm of chromosome pair 17 of Eigenmannia sp. "A" and on the short arm of pair 14 of Eigenmannia sp. "B". FISH with rDNA probes hybridized to different-sized regions between homologs, suggesting heteromorphism. The differentiation of the X chromosome in Eigenmannia sp. "B" could be the result of amplification of repetitive DNA sequences.

Espécies de Eigenmannia estão amplamente distribuídas na região Neotropical, com oito espécies válidas atualmente reconhecidas. Populações de Eigenmannia de três localidades do leste da Amazônia foram investigadas usando técnicas citogenéticas e morfológicas, revelando dois táxons designados aqui como Eigenmannia sp. "A" e Eigenmannia sp. "B". As espécies diferem em três caracteres morfométricos, dois merísticos e um osteológico. Eigenmannia sp. "A" apresenta 2n = 34 (22 m/sm+12st/a) e Eigenmannia sp. "B" apresenta 2n = 38 (14 m/sm+24st/a) e cromossomos sexuais de diferenciação simples, do tipo XX/XY. Em ambas espécies a Heterocromatina Constitutiva (HC) rica em bases A-T está distribuída na região centromérica de todos os cromossomos. Eigenmannia sp. "B" também apresenta blocos de HC na região intersticial dos pares cromossômicos 8, 9 e X que coraram positivamente para CMA3, indicando regiões ricas em G-C. A NOR está localizada no braço curto do par 17 em Eigenmannia sp. "A" e no braço curto do par 14 em Eigenmannia sp. "B". FISH com sondas de rDNA hibridizaram em regiões de tamanhos diferentes entre os homólogos, sugerindo heteromorfismo. A diferenciação do cromossomo X em Eigenmannia sp. "B" pode ser o resultado de amplificação de sequências repetitivas de DNA.

A new Hyphessobrycon (Ostariophysi: Characiformes: Characidae) from the middle Amazon basin, Brazil.

Hyphessobrycon montagi, new species, is described from tributaries of the Rio Arapiuns, a left margin affluent of the lower Rio Tapajós, Amazon basin, Pará, Brazil. The new species can be diagnosed from all its congeners by the possession of a combination of two well-defined humeral blotches, connected by a narrow stripe, and a caudal peduncle blotch. A putatively monophyletic Hyphessobrycon heterorhabdus species-group, restricted to H. heterorhabdus, H. amapaensis, and H. eschwartzae, is herein proposed based on shared derived features of color pattern. Alternative proposals of a "Hyphessobrycon heterorhabdus group" presented in the recent literature are evaluated and criticized.

The untold story of the caudal skeleton in the electric eel (ostariophysi: gymnotiformes: electrophorus).

Alternative hypotheses had been advanced as to the components forming the elongate fin coursing along the ventral margin of much of the body and tail from behind the abdominal region to the posterior margin of the tail in the Electric Eel, Electrophorus electricus. Although the original species description indicated that this fin was a composite of the caudal fin plus the elongate anal fin characteristic of other genera of the Gymnotiformes, subsequent researchers proposed that the posterior region of the fin was formed by the extension of the anal fin posteriorly to the tip of the tail, thereby forming a "false caudal fin." Examination of ontogenetic series of the genus reveal that Electrophorus possesses a true caudal fin formed of a terminal centrum, hypural plate and a low number of caudal-fin rays. The confluence of the two fins is proposed as an additional autapomorphy for the genus. Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae. Possible functional advantages to the presence of a caudal fin in the genus are discussed.

Description of a new species of Ituglanis (Siluriformes: Trichomycteridae) from Serra dos Carajás, rio Tocantins basin

A new species of Ituglanis is described from the rio Tocantins basin, State of Pará, Brazil. Ituglanis ina, new species, is distinguished from its congeners by the presence of a dark vertical bar over the base of the caudal-fin rays (vs. no bars over caudal-fin base); and by the presence of a middle trunk line of tiny neuromasts extending along the flank until the vertical through the dorsal fin, or near the caudal-fin base (vs. no middle trunk line of tiny neuromasts). Ituglanis ina can be further distinguished by a combination of characters related to color pattern and morphology. Comments on the relationship between Ituglanis species are presented.

Uma espécie nova de Ituglanis é descrita da bacia do rio Tocantins, Pará, Brasil. Ituglanis ina, espécie nova, é facilmente diferenciada das congêneres por apresentar uma barra vertical escura sobre a base dos raios da nadadeira caudal (vs. sem barras na base da nadadeira caudal); e por apresentar linha lateral seguida por uma linha de diminutos neuromastos até a região do flanco, abaixo da nadadeira dorsal, ou até o pedúnculo caudal (vs. sem neuromastos após a linha lateral). Ituglanis ina distingue-se, também, por uma combinação de caracteres relacionados ao padrão de coloração e morfologia. Comentários sobre o relacionamento das espécies e grupos de espécies de Ituglanis são apresentados.

Trichomycterus anhanga, a new species of miniature catfish related to T. hasemani and T. johnsoni (Siluriformes: Trichomycteridae) from the Amazon basin, Brazil

Trichomycterus anhanga is described from the Amazon basin, northern Brazil. The species is diagnosed by the latero-sensory system which is restricted to LL1 and LL2, the pectoral fin with two branched rays, the absence of pelvic fins and girdle, the reduced jaws and pharyngeal dentition, the presence of six to seven interopercular odontodes, the absence of a lateral series of spots, the presence of a small dark spot on the ventral surface of the mandibular symphysis, the narrow comma-shaped palatine, the absence of procurrent rays anterior to the dorsal and anal fins, the position of insertion of the first dorsal-fin pterygiophore and the presence of a single pair of pleural ribs. Trichomycterus anhanga shares with T. hasemani and T. johnsoni a wide cranial fontanel which occupies most of the skull roof. Miniaturization as well as synapomorphies for the T. hasemani group are discussed.

Trichomycterus anhanga é descrita da bacia Amazônica, norte do Brasil. A espécie é diagnosticada pelo sistema látero-sensorial restrito à LL1 e LL2, nadadeira peitoral com dois raios ramificados, ausência de nadadeiras e cintura pélvica, redução da dentição das maxilas e faringiana, presença de seis ou sete odontódeos no interopérculo, ausência de série lateral de manchas, presença de uma pequena mancha escura na superfície ventral da sínfise mandibular, palatino estreito, em forma de vírgula, ausência de raios vestigiais anteriores às nadadeiras dorsal e anal, inserção do primeiro pterigióforo da nadadeira dorsal e presença de um único par de costelas pleurais. Trichomycterus anhanga compartilha com T. hasemani e T. johnsoni a presença de fontanela craniana ampla, ocupando a maior parte do teto do crânio. A miniaturização e caracteres sinapomórficos para o grupo T. hasemani são discutidos.

Taxonomic revision of thorny catfish genus Hassar (Siluriformes: Doradidae)

The genus Hassar (Doradidae) is diagnosed by a single exclusive feature: basioccipital with ventral ring-like arch surrounding aorta; and by the combination of several non-exclusive characters, including dark blotch in distal half of anterior branched rays of dorsal fin, and anteriormost postinfranuchal scutes reduced in size. Three nominal species are recognized and redescribed in Hassar: H. orestis from the Orinoco, Essequibo and Amazonas basins, excluding Tocantins and middle to upper Xingu drainages; H. wilderi from Tocantins; and H. affinis from northeastern Brazil, including Turiaçu, Pindaré-Mearim, Itapecuru and Parnaíba drainages. The nominal Hemidoras notospilus and Hassar ucayalensis are recognized as junior synonyms of Hassar orestis; Hassar woodi is considered a junior synonym of H. affinis; Hassar iheringi is recognized as a junior synonym of H. wilderi, and its type locality as originally reported is considered incorrect. A fourth new species, Hassar gabiru, is described from middle to upper Xingu river basin. Hassar is considered to be the sister taxon of Anduzedoras + Leptodoras. A detailed anatomical description and discussion of the phylogenetic relationships of Hassar among fimbriate-barbel doradids are provided.

O gênero Hassar (Doradidae) é diagnosticado por uma característica exclusiva: extensão ventral do basioccipital formando um anel sob a aorta; e pela combinação de diversas características não-exclusivas, incluindo uma mancha escura na porção médio-distal dos raios ramificados da nadadeira dorsal, e escudos laterais anteriores reduzidos. Três espécies nominais são reconhecidas e redescritas: H. orestis das bacias do Orenoco, Essequibo e do Amazonas, excluindo Tocantins e médio e alto Xingu; H. wilderi do rio Tocantins; e H. affinis do nordeste do Brasil, incluindo os rios Turiaçu, Pindaré-Mearim, Itapecuru e Parnaíba. As espécies nominais Hemidoras notospilus e Hassar ucayalensis são reconhecidas como sinônimos juniores de H. orestis; Hassar woodi é considerado um sinônimo júnior de H. affinis; Hassar iheringi é reconhecido como sinônimo júnior de H. wilderi, e sua localidade tipo como originalmente registrada é considerada incorreta. Uma quarta e nova espécie, Hassar gabiru, é descrita do médio e alto rio Xingu. Hassar é considerado o táxon irmão de Anduzedoras + Leptodoras. Uma descrição anatômica detalhada e uma discussão sobre as relações filogenéticas de Hassar entre os doradídeos de barbilhões fimbriados também são fornecidas.

Hemigrammus arua, a new species of characid (Characiformes: Characidae) from the lower Amazon, Brazil

A new Hemigrammus species is described from tributaries of the igarapé Juruti Grande and rio Arapiuns, lower rio Amazonas, Pará State, Brazil. The new species can be easily diagnosed from all its congeners, except from Hemigrammus stictus (Durbin), by possessing a single, large humeral spot which extends longitudinally from the fifth or sixth to the posterior margin of eighth to tenth, lateral line scales. It can be distinguished from Hemigrammus stictus by possessing a pronounced upper, anteriorly-oriented extension in the humeral blotch, conferring an inverted-comma shape to it, and by displaying a distinct life color pattern.

Uma nova espécie de Hemigrammus é descrita de afluentes do igarapé Juruti Grande e do rio Arapiuns, baixo rio Amazonas, Estado do Pará, Brasil. A nova espécie pode ser facilmente diagnosticada de todos seus congêneres, exceto Hemigrammus stictus (Durbin), por possuir uma única, grande mancha umeral que se estende da quinta ou sexta escamas à margem posterior da oitava à décima escama da linha lateral. Ela pode ser distinguida de Hemigrammus stictus por possuir uma extensão da mancha umeral pronunciada e anteriormente orientada, o que lhe confere uma forma de vírgula invertida e por possuir um padrão de colorido distinto em vida.

Trichomycterus igobi, a new catfish species from the rio Iguaçu drainage: the largest head in Trichomycteridae (Siluriformes: Trichomycteridae)

A new species of Trichomycterus is described for the rio Iguaçu drainage in Southern Brazil. Trichomycterus igobi, new species, is readily distinguishable from all other species currently in the genus by its extremely large head (23.8-26.8 percent SL), which is proportionally the largest head in any Trichomycteridae. That characteristic plus the relatively deep body result in a very short-bodied overall aspect, the most extremely such case in the genus Trichomycterus. Other diagnostic features that distinguish the new species from most or all of its congeners include a short caudal peduncle (15.4-19.7 percent SL); an almost entirely cartilaginous second hypobranchial (with only vestigial ossification); a mesial expanded palatine ossification; a narrow cleithrum, falciform in shape; and the lack of a proximal posterior concavity on the third ceratobranchial. The new species seems to form a monophyletic group with T. stawiarski and other undescribed species (T. sp. C), also endemic to the rio Iguaçu. As putative synapomorphies, the three species share a rigid spine-like morphology of individual procurrent caudal-fin rays, an extended area of dorsal caudal-fin procurrent rays, and numerous branchiostegal rays (ten or eleven).

Uma nova espécie de Trichomycterus é descrita para a bacia do rio Iguaçu, sul do Brasil. Trichomycterus igobi, nova espécie, é facilmente distinguida das outras espécies atualmente no gênero por sua cabeça extremamente grande (23.8-26.8 por cento SL), que é proporcionalmente a maior em Trichomycterinae e talvez em Trichomycteridae. Esta característica, em combinação com o corpo relativamente alto, resulta em um aspecto geral atacarracado que é o mais extremo no gênero Trichomycterus. Outras características que distinguem a nova espécie da maioria ou todas as outras espécies do gênero incluem o curto pedúnculo caudal (15.4-19.7 por cento SL); segundo hipo-branquial quase inteiramente cartilaginoso (somente com ossificação vestigial); palatino expandido medialmente; cleitro estreito, de formato falciforme; e ausência de uma concavidade posterior no terceiro ceratobranquial. A nova espécie parece formar um grupo monofilético com T. stawiarski e outra espécie não descrita (T. sp. C), também endêmicas do rio Iguaçu. Como potenciais sinapomorfias, as três espécies compartilham uma morfologia rígida dos raios procurrentes caudais, que são semelhantes a espinhos; área estendida de distribuição de raios procurrentes caudais dorsais; e raios branquiostégios numerosos (10 ou 11).