425 research outputs found

    Free meals on long-distance cruisers: the vampire fish rides giant catfishes in the Amazon

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    The trichomycterid catfishes known as candirus are renowned for their blood feeding, but information on their habits under natural conditions is very fragmentary and generally restricted to hosts or habitats. We recorded an undescribed species of the vandelliine genus Paracanthopoma riding the giant jau catfish, Zungaro zungaro (Pimelodidae), in the upper Amazon. The candirus were found on the host's caudal and pectoral fins, as well as the base of the dorsal fin, with their snouts buried up to the eyes in the tough skin of the catfish host. All of them had small amounts of partly digested blood in the distal part of the gut. Along the host's dorsal fin base we found a few additional tiny holes, most of them healed. We suggest that Paracanthopoma feeds on the gill chamber of its hosts, and that the individuals we found were taking a ride partly buried into the host's skin. Our assumption seems supported by the widespread behaviour of vandelliine candirus taking blood from the gill region of their hosts, and by a report of Paracanthopoma parva found on the gills of another species of giant catfish, Brachyplatystoma vaillanti. Additionally, the Paracanthopoma sp. individuals we examined were not gorged with blood as usual for several vandelliines. Species within the genus Paracanthopoma have the longest and most robust snout, and the longest and strongest dentary teeth among blood-feeding candirus, which fit their drilling needs. Taking a ride on a giant host would be advantageous for Paracanthopoma candirus for several reasons: 1) dispersal; 2) no need to search for hosts to feed; and 3) protection from predators. The alternative explanation that Paracanthopoma takes blood from the tiny holes it drills in the skin seems unlikely, due to the recent finding that species of the genus Vandellia are unable to take blood from their hosts actively and cut open a major branchial artery to gorge themselves with blood due to the host's arterial pressure instead. The body parts of the host the Paracanthopoma sp. individuals were attached on have no large vessels that would supply them with plenty of blood. Thus, drilling a hole on a giant host skin seems to serve mostly to anchor the Paracanthopoma candirus to their long-distance cruising catfish host. If our assumption holds true, then species of this genus exemplify an instance of phoresis (hitch-hiking) among the blood-feeding candirus.Os bagres tricomicterídeos conhecidos como candirus são famosos por se alimentarem de sangue, mas as informações sobre seus hábitos, em condições naturais, são fragmentárias e restritas aos seus hospedeiros ou ambientes. Registramos uma espécie não descrita de candiru do gênero Paracanthopoma (Vandelliinae) sobre um jaú, Zungaro zungaro (Pimelodidae), no alto Rio Amazonas. Os candirus estavam sobre as nadadeiras caudal e peitoral e junto à base da dorsal, com seus focinhos enterrados até a altura dos olhos, no tegumento espesso do bagre hospedeiro. Os candirus continham pequenas quantidades de sangue parcialmente digerido na porção distal de seus tubos digestórios. Havia diversos orifícios rasos próximos à base da nadadeira dorsal do hospedeiro, a maioria cicatrizada. Sugerimos que Paracanthopoma se alimente na câmara branquial dos seus hospedeiros e que os candirus estejam viajando parcialmente enterrados na pele do jaú. Nossa suposição está apoiada no hábito de tomar sangue na região branquial dos hospedeiros, predominante entre os Vandelliinae, bem como por um registro de Paracanthopoma parva sobre as brânquias de uma outra espécie de grande bagre (Brachyplatystoma vaillanti). Além disso, os indivíduos de Paracanthopoma sp. não estavam empanturrados com sangue, como é usual para Vandelliinae. As espécies de Paracanthopoma têm o focinho mais longo e robusto entre os candirus hematófagos, além de dentes mandibulares longos e muito fortes, características adequadas ao hábito de perfurar a pele do hospedeiro. Viajar no corpo do hospedeiro seria vantajoso por diversos motivos: 1) dispersão; 2) não haver necessidade de procurar hospedeiros para se alimentar; 3) proteção contra predadores. A explicação alternativa, de que Paracanthopoma toma sangue nos pequenos furos que escava, não parece plausível, devido à recente descoberta de que espécies de Vandellia são incapazes de tomar sangue ativamente, pois fazem uma incisão numa das artérias branquiais e valem-se da pressão arterial do hospedeiro para bombear sangue dentro do seu tubo digestório. As partes do hospedeiro, em que os candirus estavam fixados, não têm vasos sangüíneos de calibre adequado para este tipo de alimentação. Portanto, escavar um furo na pele de um hospedeiro deve servir principalmente para ancorar os candirus durante os longos percursos do seu hospedeiro. Caso a nossa sugestão seja plausível, as espécies de Paracanthopoma representam um exemplo de forese em candirus hematófagos.109114Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

    Os bagres como presas de raias Potamotrygonidae nos Rios Solimões e Negro, Amazônia Brasileira

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    In spite of the fact that catfish have rarely been reported as food items in the diets of freshwater stingrays, they are commonly observed in the stomach contents of species inhabiting the Solimões and Negro rivers in the Brazilian Amazon. The stomach contents of six rays from the Solimões River and 64 from the Negro River were analyzed, and catfishes (distributed among the families Callichthyidae, Cetopsidae, Doradidae and Loricariidae) were found in the stomach contents of four and 10 of these rays, respectively, comprising a frequency of occurrence of 20%. These data indicate a relevant participation of catfishes in the diets of potamotrygonid rays in the Amazon, and may reflect the regional diversity and abundance of Siluriformes in the region

    Hemiodus langeanii (Characiformes: Hemiodontidae), a new species from rio Amana, rio Maués-Açú drainage, Amazon basin, Brazil

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    Hemiodus langeanii, new species, is described based on 20 specimens collected in the rio Amana, a tributary of rio Maués-Açú, rio Amazonas drainage, Brazil. The new taxon can be distinguished from its congeners by its high body (27.1-35.3%, average 32.3% SL vs. 18.8-28.5% in remaining species). The new species also exhibits a large lateral dark spot that is equal to, or greater than, the eye diameter (vs. smaller in remaining species except for H. microlepis). The lack of conspicuous lateral stripe or transverse bands and the low lateral line scales count (68-74) distinguish H. langeanii from some similar species in the genus (scale counts: 94-123 in H. argenteus, 124-148 in H. microlepis, 86-99 in H. orthonops and 77-92 in H. parnaguae). Finally, the new species can be differentiated from H. unimaculatus (which overlaps in the number of lateral line scales) by the higher number of scales between the lateral line and the pelvic fin origin (9-10 vs. 4-7, respectively), which are similar sized above and below lateral line (vs. scales larger bellow the lateral line in H. unimaculatus). © 2012 Sociedade Brasileira de Ictiologia

    Feeding ecology of the leaf fish Monocirrhus polyacanthus (Perciformes: Polycentridae) in a terrafirme stream in the Brazilian Amazon

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    Monocirrhus polyacanthus (Polycentridae) is a remarkable leaf-mimicking fish that inhabits streams, lake and river margins along the Amazon basin. Despite its obvious predatory habits and being frequently present in the international aquarium trade, little is known about its diet under natural conditions. We examined 35 specimens of leaf fish (28.5-82.0 mm SL), of which 19 had food the stomach. Thirty-three preys were found in the stomach contents, 19 of which were measured (2.0-33.0 mm total length). Up to five preys were found in the stomach contents of a single leaf fish specimen. The diet of the leaf fish was constituted by fish (63.15% FO, n = 12) and invertebrates (36.3% FO, n = 4); fish and invertebrate preys occurred together in three stomachs (15.8% FO). Of the 33 prey found in the stomachs, 21 were fish and 12 invertebrates. Among the consumed prey fishes, Characiformes and Perciformes represented 76.1% and 14.2% respectively. Characidae was the most commonly recorded prey family, followed by Lebiasinidae. Invertebrates were represented by shrimps (Decapoda) and insects (Coleoptera, Hymenoptera, Ephemeroptera and Odonata). There was a positive relation between the size of the leaf fish specimens and of its consumed preys. The combination of leaf fish's visually effective body camouflage and the reduced activity of the characids at crepuscular hours probably allow the capture of such fast moving preys. The coiled position of the fishes found in the stomach of M. polyacanthus possibly allowed the accommodation of more than one prey simultaneously, which seems to be important for predators that consume proportionally large preys that are captured only occasionally. © 2010 Sociedade Brasileira de Ictiologia

    Dimorfismo sexual no peixe elétrico, Gymnorhamphichthys rondoni (Rhamphichthyidae: gymnotiformes)

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    Sexual dimorfism refers to morphological differences between males and females of a species. It may be a result of different selection pressures acting on either or both sexes and may occur in any sexually-reproducing dioecious species, including fishes. We analyzed 63 females and 63 adult males of Gymnorhamphichthys rondoni (Gymnotiformes) collected by us or deposited in museum collections. Sex was identified through abdominal dissection. We measured length from snout to posterior end of anal-fin, anal-fin length, distance from anus to anal-fin origin, distance from genital papilla to anal-fin origin, body width at beginning of anal-fin, and head length. Morphometric data submitted to a Principal Component Analysis (PCA) grouped males and females according to variables related to body size (along the first component) and to head length and body height along the second and third components. Females were larger than males, whereas males had proportionally larger heads and higher bodies than females. The urogenital papilla of males and females showed differences in shape, size and relative position on the body. The female papilla was elongated horizontally, larger than that of males, and was located on a vertical line below the eye, while the papilla of the males was vertically elongated and located on a vertical line below the operculum. To our knowledge, this is the first recorded case of sexual dimorphism in a species of Rhamphichthyidae, a condition that is now known in all the currently recognized families of Gymnotiformes. © 2019, Instituto Nacional de Pesquisas da Amazonia. All rights reserved

    The diet of retroculus lapidifer (perciformes: cichlidae), a rheophilic cichlid fish from araguaia river, Tocantins State, Brazil

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    Retroculus lapidifer is a cichlid fish foraging at the bottom of Araguaia and Tocantins Rivers rapid stretches. Although being relatively abundant, little is known about its biology and ecology. This study was aimed to describe the diet of R. lapidifer and to analyze the degree of similarity (Index of Morisita) among the diets of specimens from Araguaia and Tocantins Rivers, and between specimens of R. lapidifer and R. xinguensis. Specimens of R. lapidifer were collected in the Araguaia River in four occasions from February to November 2000. INPA Fish Collection specimens were used for the diet similarity studies. One hundred stomachs of R. lapidifer (90 from Araguaia River and 10 from Tocantins River) and 11 stomachs of R. xinguensis from Xingu River were analyzed. Occurrence frequency and relative volume methods were used together as an Alimentary Index. The diet of R. lapidifer was predominantly comprised of chironomid, trichopteran and ephemeropteran immature forms. Feeding on main preys varied along the hydrologic cycle, with a decrease on the consumption of chironomids during the receding and low water level periods, balanced by an increase on the consumption of trichopterans and ephemeropterans. The similarity between the diets of Araguaia and Tocantins Rivers R. lapidifer was 0.81, and between R. lapidifer and R. xinguensis was 0.92, probably reflecting the dominance of chironomids in the diets. Retroculus lapidifer can be characterized as a predator of immature aquatics insects exploiting the variable abundance of prey types along the hydrologic cycle.Retroculus lapidifer é um ciclídeo que forrageia junto ao fundo de trechos de corredeiras dos rios Araguaia e Tocantins. Embora seja relativamente abundante, pouco se sabe sobre a biologia e ecologia dessa espécie. Este trabalho teve como objetivo conhecer a dieta de R. lapidifer, bem como analisar o grau de similaridade (Índice de Morisita) entre as dietas de exemplares dos rios Araguaia e Tocantins, e entre espécimes de R. lapidifer e R. xinguensis. Exemplares de R. lapidifer foram coletados no rio Araguaia, na cheia, vazante, seca e enchente de 2000. Nas comparações das dietas utilizou-se exemplares da Coleção de Peixes do INPA. Analisou-se 90 estômagos de R. lapidifer do rio Araguaia, 10 do Tocantins e 11 de R. xinguensis do Xingu. Utilizou-se métodos de frequência de ocorrência e volume relativo, combinados como Índice Alimentar. Houve uma predominância de formas imaturas de Chironomidae, Trichoptera e Ephemeroptera na dieta de R. lapidifer. O consumo das principais presas variou com o ciclo hidrológico, havendo um decréscimo na participação de Chironomidae na vazante e seca, compensado por um aumento no consumo de Trichoptera e Ephemeroptera. A similaridade entre as dietas de R. lapidifer dos rios Araguaia e Tocantins foi de 0,81 e entre R. lapidifer e R. xinguensis foi de 0,92, o que provavelmente reflete a predominância de Chironomidae nas dietas. Os resultados permitem caracterizar R. lapidifer como predador de formas imaturas de insetos aquáticos, que explora a abundância variável das presas ao longo do ciclo hidrológico

    ECOLOGIA COMPORTAMENTAL EVOLUTIVA APLICADA A PEIXES DE RIACHO

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    Observações diretas em campo constituem uma importante fonte de informações sobre a história natural e o comportamento de peixes de riacho. Contudo, tais observações diretas podem ser insuficientes para permitir conclusões robustas sobre as causas dos fenômenos biológicos envolvidos, já que dados observacionais frequentemente falham em demonstrar de forma contundente relações de causa e efeito. Neste estudo nós trazemos conceitos necessários para a formulação de hipóteses a partir de uma versão derivada da História Natural e da Etologia, a Ecologia Comportamental Evolutiva. Essaperspectiva permite análises do contexto evolutivo e do valor adaptativo dos padrões comportamentais observados, e serve de base para novas hipóteses que podem ser aplicadas a muitos grupos de organismos. Observações e experimentos envolvendo peixes de riacho originaram e deram subsídio a muitas teorias sobre a evolução de comportamentos e de características morfológicas peculiares que são amplamente debatidas pela comunidade científica. Após apresentar os conceitos chaves, nós trazemos alguns exemplos de programas de pesquisas com peixes que culminaram na formulação de importantes teorias, onde cientistas aproveitaram as oportunidades que os peixes de riacho oferecem e conduziramobservações, amostragens e experimentos controlados em campo e laboratório. Descrevemos nosso programa de pesquisas, que tem uma espécie amazônica de peixe de riacho (Crenuchus spilurus) como organismo modelo. Ao final, advogamos pela pluralidade de métodos e análises no estudo da Ecologia Comportamental Evolutiva de peixes de riacho.BEHAVIORAL EVOLUTIONARY ECOLOGY - WITH APPLICATIONS TO FRESHWATER STREAM FISH: Direct field observation constitutes an important source of information on life history and behavior ofstream fish. Unfortunately, information gathered from direct field observations are often limited and thus may fail to provide robust testing for the causation of biological phenomena. Here, we bring concepts that form the theoretical foundation necessary for raising hypotheses in Evolutionary Behavioral Ecology,a study area directly derived from natural history and ethology that directly incorporates evolutionary processes and the adaptative value of behavioral patterns observed. This perspective allows the analysisof the evolutionary context and the adaptive value of observed behavioral patterns, and serves as the basis for new hypotheses that can be applied to many groups of organisms. Using this framework, field observations and experiments encompassing freshwater stream fish have subsidized many theories on the evolution of behavioral and morphological traits that are widespread debated by scientific community. After presenting the main key concepts, we bring some examples of research programs with freshwater fish that culminated in the formulation of important theories and where scientists took advantage of the opportunities provided by stream fish to conduct observations, samplings and controlled experiments both in the field and in captivity. We also describe our own research program, which uses an Amazonian freshwater stream fish (Crenuchus spilurus) as a model organism. By doing so, we advocate for the use of several methods and analyses for the study of Evolutionary Behavioral Ecology of freshwater stream fish

    Sampling effort and fish species richness in small terra firme forest streams of central Amazonia, Brazil

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    Small streams are important components of the landscape in terra firme forests in central Amazonia and harbor a large number of fish species. Nevertheless, the lack of a common sampling protocol in studies of this ichthyofauna hinders comparisons among available results. This study evaluates how the length of stream reach sampled affects estimates of local fish species density in 1st, 2nd, and 3rd order streams, and proposes a mean minimum sampling length that best approximates the absolute number of species in a given stream segment. We sampled three streams in the Biological Dynamics of Forest Fragments Project's study sites, between May and August 2004. At each stream, one 1st order, one 2nd order, and one 3rd order segment was sampled. We sampled five 20-m reaches in each stream segment. Three to four people collected along each reach for 45 to 60 minutes. We used Jaccard's coefficient to estimate the similarity of species composition among stream reaches and segments. Estimates of species richness were obtained with Jackknife 1 and Bootstrap algorithms and species accumulation curves. We used simple linear regressions to look for relationships between species density and fish abundance and between species density and the volume of 100-m stream segments. Species density in 1st order stream reaches was slightly higher than in 2nd and 3rd order stream reaches, whereas fish abundance was apparently higher in 3rd order reaches. Similarity in fish species composition between 20-m reaches was low for all studied streams. Species density values in pooled 100-m stream segments represented 71.4% to 94.1% of the estimated values for these streams. Species density showed a direct relationship both with volume of the sampled stream segment and fish abundance. It seems plausible that larger streams contain a higher number of microhabitat types, which allow for the presence of more fish species per stream length. Based on the values of asymptotes and equations for species accumulation curves, the mean minimum sampling length that best estimates the absolute number of species in a stream segment is 180 m ± 20 sd for 1st order segments; 213 m ± 23 sd for 2nd order segments, and 253 m ± 30 sd for 3rd order stream segments. Copyright © 2007 Sociedade Brasileira de Ictiologia

    Sampling effort and fish species richness in small terra firme forest streams of central Amazonia, Brazil

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    Small streams are important components of the landscape in terra firme forests in central Amazonia and harbor a large number of fish species. Nevertheless, the lack of a common sampling protocol in studies of this ichthyofauna hinders comparisons among available results. This study evaluates how the length of stream reach sampled affects estimates of local fish species density in 1st, 2nd, and 3rd order streams, and proposes a mean minimum sampling length that best approximates the absolute number of species in a given stream segment. We sampled three streams in the Biological Dynamics of Forest Fragments Project's study sites, between May and August 2004. At each stream, one 1st order, one 2nd order, and one 3rd order segment was sampled. We sampled five 20-m reaches in each stream segment. Three to four people collected along each reach for 45 to 60 minutes. We used Jaccard's coefficient to estimate the similarity of species composition among stream reaches and segments. Estimates of species richness were obtained with Jackknife 1 and Bootstrap algorithms and species accumulation curves. We used simple linear regressions to look for relationships between species density and fish abundance and between species density and the volume of 100-m stream segments. Species density in 1st order stream reaches was slightly higher than in 2nd and 3rd order stream reaches, whereas fish abundance was apparently higher in 3rd order reaches. Similarity in fish species composition between 20-m reaches was low for all studied streams. Species density values in pooled 100-m stream segments represented 71.4% to 94.1% of the estimated values for these streams. Species density showed a direct relationship both with volume of the sampled stream segment and fish abundance. It seems plausible that larger streams contain a higher number of microhabitat types, which allow for the presence of more fish species per stream length. Based on the values of asymptotes and equations for species accumulation curves, the mean minimum sampling length that best estimates the absolute number of species in a stream segment is 180 m ± 20 sd for 1st order segments; 213 m ± 23 sd for 2nd order segments, and 253 m ± 30 sd for 3rd order stream segments. Copyright © 2007 Sociedade Brasileira de Ictiologia
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