Drift of Colomesus asellus (Teleostei : Tetraodontidae) larvae in the Amazon river

#Colomesus asellus est le seul #Tetraodontidae du bassin amazonien, ce qui rend possible l'identification des larves et l'étude de leur transport par le fleuve. Durant un an, nous avons échantillonné le cours de l'Amazone et le long des berges. Nous observons une dérive durant la crue, lorsque les larves sont transportées passivement vers les lacs de la plaine inondée. Le long des berges, la densité des larves est significativement plus importante que dans le milieu du fleuve, mais elle n'est pas homogène, ce qui laisse supposer que la ponte se réalise dans des sites spécifiques, près de la berge. La stratégie de reproduction de #C. asellus diffère de celle des autres poissons d'eau douce de colonisation secondaire (#Scianenidae, #Engraulidae$ et autres) et des autres tétraodontes d'eau douce, mais elle se rapproche de la stratégie des Characiformes et Siluriformes ainsi que de celle des tétraodontes marins. (Résumé d'auteur

Drift of Colomesus asellus (Teleostei : Tetraodontidae) larvae in the Amazon river

#Colomesus asellus est le seul #Tetraodontidae du bassin amazonien, ce qui rend possible l'identification des larves et l'étude de leur transport par le fleuve. Durant un an, nous avons échantillonné le cours de l'Amazone et le long des berges. Nous observons une dérive durant la crue, lorsque les larves sont transportées passivement vers les lacs de la plaine inondée. Le long des berges, la densité des larves est significativement plus importante que dans le milieu du fleuve, mais elle n'est pas homogène, ce qui laisse supposer que la ponte se réalise dans des sites spécifiques, près de la berge. La stratégie de reproduction de #C. asellus diffère de celle des autres poissons d'eau douce de colonisation secondaire (#Scianenidae, #Engraulidae$ et autres) et des autres tétraodontes d'eau douce, mais elle se rapproche de la stratégie des Characiformes et Siluriformes ainsi que de celle des tétraodontes marins. (Résumé d'auteur

O efeito da floresta alagada na alimentação de três espécies de peixes onívoros em lagos de várzea da Amazônia Central, Brasil Effects of flooded forest in the diet of three fish species in floodplain lakes of Central Amazon, Brazil

As enchentes anuais dos rios na Amazônia alagam extensas áreas de floresta conhecidas como várzeas ou igapós. Estas áreas têm papel importante na vida dos peixes da região, pois são fontes de alimento e de abrigo. Acreditamos que o desmatamento destas áreas ocasiona prejuízos à ictiofauna principalmente pela diminuição da quantidade e diversidade de alimento disponível. O estudo da relação entre a quantidade de floresta e a dieta de Parauchenipterus galeatus (Auchenipteridae, Siluriformes), Mylossoma duriventre (Characidae, Characiformes)e Triportheus elongatus (Characidae, Characiformes)permitiu registrar pela primeira vez a influência direta da floresta alagada na ecologia alimentar de peixes na Amazônia Central.<br>The annual flooding of the rivers in the Amazonia extends over large forest areas known as várzeas or igapós. These areas play an important role in the life of the fishes, as a source of food and shelter. We believe that the deforestation of these areas may affect negatively the fish fauna mainly by decreasing the amount of food resources and consequently the diversity of food types available. The study of the relationship between the riparian forest cover and the diet of Parauchenipterus galeatus (Auchenipteridae, Siluriformes), Mylossoma duriventre (Characidae, Characiformes) and Triportheus elongatus (Characidae, Characiformes) allowed to refer for the first time on the direct influence of the flooded forest in the feeding ecology of fishes in Central Amazonia

Morphological description of larvae of the Mapar\ue1 Hypophthalmus edentatus (Spix) (Osteichthyes, Hypophthalmidae) in the Itaipu reservoir (Parana River, Brazil)

The ontogenetic aspects of larvae of Hypophthalmus edentatus (Spix, 1829) from the ichthyoplankton samples collected in the Itaipu reservoir between March 1988 and April 1990 were analysed. Sample were caught by 0.5 mm mesh conic-cylindrical plankton net. Larvae of H. edentatus were identified and described as Siluriforms from the morphological and morphometric development series. They have a small to medium-sized head, long body, small eyes, little pigmentation, mandibular barbules and 53 to 56 myomeres. High values obtained with correlation coefficient (r > 0.97; p < 0.001) show that growth was proportional in different parts of the body

Larval development of Plagioscion squamosissimus (Heckel) (Perciformes, Sciaenidae) of Itaipu reservoir (Paraná river, Brazil)

The aim of the present study was to characterize the larval development of Plagioscion squamosissimus (Heckel, 1840) morphometrically, collected at Itaipu reservoir from March 1988 to April 1990. It was obtained the samples monthly, with a conic-cylindrical plankton net with 0.5mm mesh. The morphological description of the larvae of P. squamosissimus was based on different stages of development. The specimens less than 6mm long present a moderate sized head and those that are larger than this length, present a large head. The pectoral fins are in an elevated position, near the operculum bones, and the ventral fins are in thoracic positions, the body has a moderate height, the eyes are small to moderate and the mouth is large with caniniform teeth. This species presents a proportional growth among the different parts of the body, as can be seen by the high correlation coefficient values (r>0.98; p<0.001)

Alimentação e ecomorfologia de duas espécies de piranhas (Characiformes: Characidae) do lago de Viana, estado do Maranhão, Brasil Feeding and ecomorphology of two species of piranhas (Characiformes: Characidae) from the Viana Lake, Maranhão state, Brazil

Serrasalmus aff. brandtii e Pygocentrus nattereri são duas espécies de piranhas comuns no Lago de Viana, um lago formado a partir das inundações do Rio Pindaré, tributário da margem esquerda do Rio Mearim. Uma amostra composta por 249 exemplares destas espécies foi estudada a fim de identificar a composição da dieta e as estratégias alimentares empregadas pelas duas. Os peixes foram coletados trimestralmente durante um ano, entre março de 1998 e março de 1999, usando redes de emalhar e tarrafas. A composição qualitativa da dieta foi analisada com uso do método de freqüência de ocorrência. As estratégias alimentares empregadas pelas espécies foram inferidas através do método gráfico de Costello (1990), modificado por Amundsen et al. (1996). Os resultados indicaram que peixes foi o item encontrado com maior freqüência nos estômagos de ambas as espécies, seguido de matéria vegetal, com maior participação na dieta de P. nattereri. Os recursos peixes e vegetais tenderam a apresentar relações inversas quando comparados com as diferentes classes de comprimento. A análise gráfica da dieta de P. nattereri e S. aff. brandtii sugere que a maioria dos indivíduos utiliza vários recursos simultaneamente. Uma análise multivariada de índices ecomorfológicos indicou que as espécies são segregadas com relação à habilidade natatória, posição ocupada na coluna d'água e tamanho relativo das presas.<br>Serrasalmus aff. brandtii and Pygocentrus nattereri are two species of piranhas, both common in the Viana Lake, which is formed by the flooding waters of the Pindaré River, a tributary of the left bank of the Mearim River. A sample composed of 249 specimens of these species was studied in order to identify diet composition and feeding strategies employed by the two species. The piranhas were captured thrimonthly, during one year from March 1998 to March 1999 using gill and fishing nets of different mesh sizes. The qualitative composition of the diet was analysed through the frequency of occurrence method. The feeding strategies employed by the piranhas were inferred using the graphic method of Costello (1990), modified by Amundsen et al. (1996). The results indicated that fish was the main food item in the stomach contents of the two species, followed by plant material, more in the P. nattereri. Fish and plant material showed different relationships in relation to piranhas's length classes. The graphic analysis of the feeding strategies employed by P. nattereri and S. aff. brandtii suggest a generalist habit, wide width niche with strong participation of the within-phenotype component, which indicated that the majority of individuals of these species use several resources simultaneously. A multivariate analysis of the ecomorphological index indicated that the species are discriminated by swimming ability, water column position and relative prey size