Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin

Abstract The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Resumo O objetivo deste estudo foi determinar a ecologia trófica de juvenis e adultos de Acestrorhynchus falcirostris durante o período de enchente e cheia em seis lagos de ilha adjacentes ao rio Solimões. Assim, investigamos: i) a posição trófica, através do nicho trófico fracional; ii) a largura de nicho; iii) sobreposição de nicho; iv) a estratégia alimentar. Os espécimes foram coletados durante os anos de 2014 a 2017, utilizando redes de emalhar com malha variando de 30 a 120mm entre nós opostos. Por meio da análise do conteúdo estomacal, observamos a preferência no consumo de itens de origem animal. Os juvenis consumiram insetos em maiores proporções (IAi% = 50%), enquanto os adultos consumiram preferencialmente peixes (IAi% = 99,98%). Apesar da grande oferta de alimentos disponíveis no período da cheia, os juvenis eram os únicos a consumir itens de origem alóctone, como por exemplo, os insetos. Os juvenis apresentaram uma estratégia alimentar e composição alimentar diferente para os adultos. Os juvenis foram considerados onívoros com uma estratégia generalista, enquanto os adultos foram considerados piscívoros com uma estratégia alimentar mais especialista. Assim, a composição alimentar, amplitude do nicho, posição trófica e a estratégia alimentar de Acestrorhynchus falcirostris muda em função do estágio de desenvolvimento.

Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin / Ecologia trófica de Acestrorhynchus falcirostris Cuvier, 1819 em lagos de ilha no trecho inferior do Rio Solimões, Bacia Amazônica

Abstract The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Resumo O objetivo deste estudo foi determinar a ecologia trófica de juvenis e adultos de Acestrorhynchus falcirostris durante o período de enchente e cheia em seis lagos de ilha adjacentes ao rio Solimões. Assim, investigamos: i) a posição trófica, através do nicho trófico fracional; ii) a largura de nicho; iii) sobreposição de nicho; iv) a estratégia alimentar. Os espécimes foram coletados durante os anos de 2014 a 2017, utilizando redes de emalhar com malha variando de 30 a 120mm entre nós opostos. Por meio da análise do conteúdo estomacal, observamos a preferência no consumo de itens de origem animal. Os juvenis consumiram insetos em maiores proporções (IAi% = 50%), enquanto os adultos consumiram preferencialmente peixes (IAi% = 99,98%). Apesar da grande oferta de alimentos disponíveis no período da cheia, os juvenis eram os únicos a consumir itens de origem alóctone, como por exemplo, os insetos. Os juvenis apresentaram uma estratégia alimentar e composição alimentar diferente para os adultos. Os juvenis foram considerados onívoros com uma estratégia generalista, enquanto os adultos foram considerados piscívoros com uma estratégia alimentar mais especialista. Assim, a composição alimentar, amplitude do nicho, posição trófica e a estratégia alimentar de Acestrorhynchus falcirostris muda em função do estágio de desenvolvimento.

Flood pulse influence on the feeding ecology of two Amazonian auchenipterid catfishes

We assessed the flood pulse effect on the diet composition, trophic niche breadth, and the amount of food intake of two Amazonian auchenipterids with different feeding strategies. Sampling was carried out quarterly (from April/2012 to January/2014) on the middle Xingu River, using gillnets. We measured specimens for standard length and total weight. The specimens' stomachs were removed, weighed, and had their contents identified. We analyzed 360 stomachs of Auchenipterus nuchalis and 584 of Tocantinsia piresi. The diet of A. nuchalis was mainly composed of aquatic insects and crustaceans, while T. piresi fed on fruits and seeds. The diet composition of both species varied seasonally, but only T. piresi changed its trophic niche breadth in response to hydrological changes, becoming more specialist during the higher water periods (filling and flood). Both species also showed differences in their amount of food intake between hydrological periods, with A. nuchalis feeding more intensely in lower water periods (ebb and dry), while T. piresi in the higher water periods. We evidenced different responses to the hydrological periods for the related species. We emphasize that studies considering the relationship between flood pulse and feeding ecology of the organisms are essential to understanding river floodplain systems' dynamics.(AU)

Avaliamos o efeito do pulso de inundação na composição da dieta, amplitude de nicho trófico e quantidade de alimento ingerido de dois auchenipterídeos amazônicos com diferentes estratégias alimentares. Os espécimes foram amostrados trimestralmente entre abril/2012 e janeiro/2014 no médio rio Xingu, utilizando malhadeiras. Estes foram mensurados quanto ao comprimento padrão e peso total. Os estômagos dos espécimes foram removidos, pesados e seu conteúdo identificado. Analisamos 360 estômagos de Auchenipterus nuchalis e 584 de Tocantinsia piresi. A dieta de A. nuchalis foi predominantemente composta por insetos aquáticos e crustáceos, enquanto para T. piresi frutos e sementes predominaram. A composição da dieta de ambas as espécies variou sazonalmente, mas apenas para T. piresi a amplitude de nicho trófico variou entre períodos hidrológicos, sendo mais especialista nos períodos de águas altas (enchente e cheia). Ambas as espécies diferiram na quantidade de alimento ingerido entre os períodos hidrológicos, sendo maior para A. nuchalis nos períodos de águas baixas (vazante e seca) e para T. piresi nos períodos de águas altas. Evidenciamos diferentes respostas à variação hidrológica pelas espécies. Enfatizamos que estudos considerando a relação entre a dinâmica do pulso de inundação e a ecologia alimentar dos organismos é fundamental para um melhor entendimento da dinâmica das planícies de inundação.(AU)

Damming in the Madeira River modifies the food spectrum of piscivorous and affects their resource partitioning

Phylogenetic proximity suggests some degree of diet similarity among species. Usually, studies of diet show that species coexistence is allowed by partitioning food resources. We evaluate how visually oriented piscivorous fishes (Characiformes) share prey before and after building the Santo Antônio Hydroelectric Power Plant (HPP) in the Madeira River (Brazil), the largest muddy-water tributary of the Amazon River. Piscivorous species (Acestrorhynchus falcirostris, Acestrorhynchus heterolepis, Hydrolycus scomberoides, and Rhaphiodon vulpinus) were sampled under pristine (pre-HPP) and disturbed (post-HPP) environmental conditions. We analyzed species abundance and stomach contents for stomach fullness and prey composition to check variations between congeneric and non-congeneric species. The percent volume of prey taxa was normalized by stomach fullness and grouped into the taxonomic family level to determine diet, niche breadth, and overlap. Only R. vulpinus abundance increased in post-HPP. There was no significant variation in niche breadth between the periods, while niche overlap decreased in congeneric and non-congeneric species. Our results indicate that river impoundment affected piscivorous fishes in distinct ways and modified their resource partitioning. Therefore, evaluate interspecific interactions is a required tool to understand how fishes respond to river damming.(AU)

A proximidade filogenética pode indicar similaridade da dieta entre espécies e a partilha de recursos alimentares é um mecanismo que possibilita a coexistência. Neste trabalho, avaliamos como peixes piscívoros compartilham presas antes e depois da construção da Usina Hidrelétrica (UHE) Santo Antônio no rio Madeira (Brasil), o maior afluente de águas brancas do rio Amazonas. Espécies piscívoras (Acestrorhynchus falcirostris, Acestrorhynchus heterolepis, Hydrolycus scomberoides e Rhaphiodon vulpinus) foram coletadas em condições ambientais pristinas (pré-HPP) e impactadas (pós-HPP). Nós avaliamos as abundâncias e as dietas para identificar variações entre as espécies congenéricas e não-congenéricas. O percentual de volume de cada presa foi corrigido pelo grau de repleção estomacal e os itens agrupados ao nível taxonômico de família para determinar dieta, amplitude e sobreposição alimentar. Apenas a abundância de R. vulpinus aumentou no pós-HPP. Não houve diferença na amplitude alimentar das espécies após o represamento, contudo a sobreposição de nicho diminuiu para as espécies congenéricas e não congenéricas. Nossos resultados indicam que o represamento do rio afetou os peixes piscívoros modificando sua partilha de recursos. Avaliar as interações interespecíficas, portanto, é uma ferramenta necessária para entender como os peixes respondem ao represamento de rios.(AU)

Do local environmental factors structure the trophic niche of the splash tetra, Copella arnoldi? A test in an Amazonian stream system

Environmental variation affects the availability of spatial and trophic resources in Amazonian streams and may be important factors structuring the diet of fishes. We analyzed the diet composition and trophic niche breadth of the lebiasinid splash tetra, Copella arnoldi, aiming to evaluate how environmental variation in Amazonian streams affects the species' trophic niche. Fish were captured and environmental factors were recorded in 20 streams in the Caxiuanã National Forest, in the eastern Amazon, in November 2010. We made a semi-quantitative analysis of stomach contents of 200 individuals. Copella arnoldi exhibited an omnivorous diet composed mainly of detritus and allochthonous invertebrates. Environmental variation (stream width, stream depth, canopy cover and flow) did not affect the diet composition or trophic niche breadth of the species, possibly due to the regional integrity of the forest within the boundaries of the protected area. Riparian cover probably minimizes the effect of the small-scale variations in food resources, thus leading to a locally homogeneous diet composition in the splash tetra C. arnoldi. (AU)

Diet and trophic niche overlap of Boana bischoffi and Boana marginata (Anura: Hylidae) in southern Brazil / Dieta e sobreposição de nicho trófico de Boana bischoffi e Boana marginata (Anura: Hylidae) no sul do Brasil

Abstract: The species Boana bischoffi and Boana marginata are endemic to the Atlantic Forest, where they often occur in sympatry. There is a large gap in the knowledge of natural history of both species. In this study, we aimed to describe and compare the diet composition of B. bischoffi and B. marginata in the southern domain of the Brazilian Atlantic Forest. We analyzed the gastrointestinal contents of 43 individuals of B. bischoffi and 30 individuals of B. marginata. Both showed a high trophic niche overlap (0.90 Ojk). The most important prey categories for both species belonged to the orders Araneae and Coleoptera. The species niche breadth (Bsta) varied from 0.35 to 0.42, suggesting a generalist feeding behavior for both species. Our data provide unprecedented information on these species' food composition, contributing to a better knowledge of the natural history of neotropical anurans.

Resumo: As espécies Boana bischoffi e Boana marginata, são endêmicas da Mata Atlântica onde frequentemente ocorrem em simpatria. Existe uma grande lacuna no conhecimento da história natural de ambas as espécies. Nesse estudo, nosso objetivo foi descrever e comparar a composição da dieta de B. bischoffi e B. marginata no limite sul da Mata Atlântica brasileira. Analisamos o conteúdo gastrointestinal de 43 indivíduos de B. bischoffi e 30 indivíduos de B. marginata. Ambas apresentaram elevada sobreposição de seus nichos tróficos (0,90 Ojk). As categorias de presas mais importantes para ambas as espécies pertenciam as ordens Araneae e Coleoptera. A amplitude de nicho das espécies (Bsta) variou de 0,35 a 0,42, sugerindo comportamento alimentar generalista para ambas. Nossos dados trazem informações inéditas sobre a composição alimentar destas espécies, contribuindo para um maior conhecimento da história natural dos anuros neotropicais.

Comparative feeding ecology of four syntopic Hypostomus species in a Brazilian southeastern river / Ecologia alimentar comparativa de quatro espécies simpátricas de Hypostomus em um rio do sudoeste brasileiro

Abstract Though their broad distribution in most Brazilian rivers, scarce studies concerning ecological interactions on Hypostomus species are available. This study observes the diet, the trophic interactions and some morphological aspects of four syntopic species of Hypostomus. These fishes were studied at the superior part of the Corumbataí river, at São Paulo state, southeastern Brazil. Analyses focused feeding patterns, their amplitude and whether there happens some food items overlap among the species. Fish were caught using cast nets at some points of the river. Species were chosen according to their local abundance and, so there were four main species: H. albopunctatus, H. ancistroides, H. regani and H. strigaticeps. Nine food items were found: sediments, fungi, diatoms, green algae, Tecamoeba, vegetal debris and invertebrates. There were not significant differences for the feeding pattern among the four Hypostomus species. The feeding niche amplitude has been larger for H. albopunctatus influenced by a larger amount of vegetal debris and invertebrates. Elevated niche overlap was found to happen among the species and also for their trophic morphology. Results may suggest that there is a similar pattern in food taken between four species of Hypostomus analyzed since all consume similar environmental resources and have similar anatomical features. However, a different intake insect larvae and plant material in H. albopunctatus diet indicate differences in local and how this species may be exploring their food compared to the others.

Resumo Apesar de sua grande distribuição em todos rios brasileiros, poucos estudos estão disponíveis sobre as interações ecológicas do gênero Hypostomus. Neste estudo nós examinamos a dieta, as interações tróficas e a morfologia de quatro espécies sintópicas de Hypostomus sp. no trecho superior do rio Corumbataí, estado de São Paulo no sudeste do Brasil. As análises focaram o padrão alimentar, a amplitude e sobreposição de nicho alimentar e a correlação entre a dieta com características da morfologia. A captura dos exemplares foi realizada com o uso de redes de arremesso (tarrafa) ao longo do leito do rio. O critério adotado para a escolha baseou-se nas espécies de maior abundância no local, chegando a quatros espécies principais: H. albopunctatus, H. ancistroides, H. regani e H. strigaticeps. Foram encontrados nove itens alimentares: sedimento grosso e fino, hifas de fungos, diatomáceas, algas verdes, algas azuis, Tecamoeba, restos de material vegetal e invertebrados, não havendo diferenças significativas no padrão alimentar entre as quatro espécies de Hypostomus. A amplitude de nicho alimentar foi maior para H. albopunctatus influenciada por um maior consumo de material vegetal e invertebrados. Foram encontrados altos valores de sobreposição de nicho alimentar além de uma similaridade entre a dieta e a morfologia trófica entre as espécies consideradas. Os resultados sugerem que exista um padrão semelhante na tomada de alimento entre as quatros espécies de Hypostomus analisadas, uma vez que, todas consomem recursos alimentares semelhantes e possuam características anatômicas semelhantes. No entanto, uma ingestão diferenciada de larvas de insetos e material vegetal na dieta de H. albopunctatus indicam diferenças nos locais e na forma como esta espécie pode estar explorando o seu alimento em comparação com as demais.

Feeding ecology of Serrasalmus gouldingi (Characiformes: Serrasalmidae) in the lower Anapu River region, Eastern Amazon, Brazil / Ecologia alimentar de Serrasalmus gouldingi (Characiformes: Serrasalmidae) na região do baixo Rio Anapu, Amazônia Oriental, Brasil

Studies on feeding ecology of fishes are important to understand the relationship between species and environmental seasonal variations. In tropical rivers, these relationships are mainly modeled by hydrological patterns. Thereby, this study aimed to assess the influence of fluviometric variation and life stage (juveniles and adults) in the feeding ecology of Serrasalmus gouldingi in the lower Anapu River region, located in Eastern Amazon, Pará, Brazil. Specimens were collected bimonthly, considering four different hydrological periods. We assessed the diet composition, feeding intensity and niche breadth of the species. Thirty-two dietary items were identified and grouped into ten categories. A total of 279 stomachs were analyzed, showing a predominance of fish fragments, followed by fruits and seeds. The diet composition of S. gouldingi differed only between drought and flood season, although it did not differ between juveniles and adults. An increase in feeding intensity was recorded during the rise in the water level, with a lower feeding intensity observed during transitional season. Serrasalmus gouldingi showed lower niche breadth during flood season, attributed to the high consumption of fruits and seeds, presenting an omnivorous diet with high tendency towards piscivory. Although less evident than in other Amazon watersheds, the flood pulse in the lower Anapu River region is an important factor influencing the feeding ecology of the species.

Estudos sobre ecologia trófica dos peixes são importantes ferramentas para compreensão das relações entre as espécies e as variações sazonais no ambiente. Em rios tropicais essas relações são modeladas principalmente por variações hidrológicas. Sendo assim, o objetivo presente estudo é avaliar a influência variação fluviométrica e do estágio de vida (juvenis e adultos) na ecologia alimentar de Serrasalmus gouldingi na região do baixo Rio Anapu, Amazônia Oriental, Pará, Brasil. Os espécimes foram amostrados bimensalmente considerando quatro períodos hidrológicos distintos. Nós avaliamos a composição da dieta, intensidade alimentar e amplitude de nicho da espécie. Foram identificados trinta e dois itens alimentares agrupados em dez categorias. Um total de 279 estômagos foi analisado, registrando um predomínio no consumo de fragmento de peixes seguido por frutos e sementes. A composição na dieta de S. gouldingi diferiu apenas entre os períodos de seca e cheia, não diferindo entre juvenis e adultos. Uma maior intensidade alimentar foi observada durante o aumento do nível dos rios, com uma menor intensidade alimentar durante os períodos transicionais. Durante o período de cheia S. gouldingi também evidenciou uma menor amplitude de nicho, a qual foi atribuída ao elevado consumo de frutos e sementes. Sendo assim, a dieta de S. gouldingi foi classificada como onívora com forte tendência a piscivoria. Embora menos evidente do que em outras regiões da Amazônia, o pulso de inundação na região do baixo Rio Anapu também afeta a ecologia alimentar da espécie.

DIET OF DIRECT-DEVELOPING FROGS (ANURA: CRAUGASTORIDAE: Pristimantis) FROM THE ANDES OF WESTERN COLOMBIA / Dieta de ranas de desarrollo directo (Anura: Craugastoridae: Pristimantis) de los Andes occidentales de Colombia

We studied the diet of 15 montane frog species of the genus Pristimantis (Craugastoridae) from the Andes of Western Colombia to determine the diet range, breadth of niche and overlap among species. We identified 499 prey items from stomach and intestinal contents of 154 specimens. Prey items were included in 74 different categories. The most common 15 prey categories accounted for 65 % of all frogs' diet. The invertebrate families Isotomidae, Chironomidae, Formicidae, and Tipulidae were the most abundant categories and accounted for 32 % of the frogs' diet. Ten of the 15 frog species were found with at least one item of Araneae. Coleoptera and Tipulidae were found in nine frog species, and Acari and Carabidae in eight frog species. In general, beetles were found in gastrointestinal tracts of all species examined, except for P. quantus, but interpretation needs caution because only one individual of this species was caught. Pristimantis hectus showed a specialized diet, consuming mainly dipterans of the family Chironomidae, while the remaining species showed a generalist diet. Pristimantis palmeri showed niche overlap with P. erythropleura (Фjk = 0.69), P. myops (Фjk = 0.64), and P. orpacobates (Фjk = 0.64). Our results suggest that most of the frogs species studied are generalist, foraging opportunistically on dipterans, arachnids, collembolans, coleopterans, and hymenopterans. Here, we report the diet of montane Pristimantis species and discuss the results in comparison with data on related species in montane and lowland regions.

Estudiamos la dieta de 15 especies de ranas montanas del género Pristimantis (Craugastoridae) en la Cordillera Occidental de Colombia para determinar su variación, amplitud y traslape de nicho. En los contenidos estomacales e intestinales de 154 especímenes se identificaron 499 presas que fueron organizadas en 74 categorías diferentes. Las 15 categorías de presas más comunes representaron el 65 % de la dieta. Las familias de invertebrados Isotomidae, Chironomidae, Formicidae y Tipulidae fueron las más abundantes, representando el 32 % de la dieta de las ranas. Diez de las 15 especies de ranas presentaron al menos un ítem de Araneae. Coleoptera y Tipulidae fueron otras categorías frecuentemente encontradas en los tractos digestivos de las ranas (nueve especies de ranas presentaron estos ítems), seguidas de Acari y Carabidae (ocho especies). En general, los escarabajos fueron encontrados en los tractos gastrointestinales de todas las especies, excepto en P. quantus, pero este resultado debe tratarse con precaución porque solo un individuo de esta especie fue capturado. Pristimantis hectus mostró una dieta especializada consumiendo principalmente dípteros de la familia Chironomidae, mientras que las especies restantes mostraron una dieta generalista. Pristimantis palmeri presentó superposiciones de nicho con P. erythropleura (Фjk = 0,69), P. myops (Фjk = 0,64), y P. orpacobates (Фjk = 0,64). Nuestros resultados sugieren que la mayoría de las especies estudiadas son generalistas que se alimentan de manera oportunista de dípteros, arácnidos, colémbolos, coleópteros e himenópteros. Aquí, reportamos la dieta de especies montanas de Pristimantis y discutimos los resultados con datos de otros estudios en especies relacionadas de regiones montanas y tierras bajas.

ECOLOGÍA ALIMENTARIA DE LA RANA DE LLUVIA ENDÉMICA Pristimantis jubatus (CRAUGASTORIDAE) EN EL PARQUE NACIONAL NATURAL MUNCHIQUE, COLOMBIA / Feeding Ecology of the Endemic Rain Frog Pristimantis jubatus (Craugastoridae) in Munchique National Park, Colombia

Se estudió la dieta de la rana de lluvia Pristimantis jubatus con base en los contenidos estomacales e intestinales de 29 individuos colectados en tres diferentes localidades del Parque Nacional Natural Munchique, Colombia. La dieta estuvo compuesta exclusivamente de artrópodos, identificándose un total de 66 presas correspondientes a 32 taxa. Diptera e Hymenoptera fueron los artrópodos más frecuentemente encontrados, 19,7 % y 16,7 % respectivamente, seguidos de Araneae (15,1 %) y de Coleoptera (12,1 %). Esta especie no mostró preferencia por ninguno de los tipos de presa y presentó un alto valor de amplitud de nicho (0,68), lo cual indica una dieta generalista. Adultos y juveniles forrajean en diferentes alturas de percha, encontrándose los primeros a alturas mayores que los segundos. El número de categorías encontradas y el uso del hábitat muestran a P. jubatus como una especie que puede consumir oportunamente cualquier artrópodo disponible en los estratos del bosque donde forrajea.

We studied the diet of the rain frog Pristimantis jubatus based on stomach and intestinal contents of 29 individuals from three different localities at Munchique National Park, Colombia. The diet was composed exclusively of arthropods, comprising a total of 66 prey which were in 32 taxa. The most frequent dietary items were Diptera and Hymenoptera, 19.7 % and 16.7 % respectively, followed by Araneae (15.1 %) and Coleoptera (12.1 %). Plant consumption was considered incidental because of its low frequency. This species showed no preference for any type of prey, with a high value of niche breadth (0.68) indicating a generalist diet. Adults and juveniles occupy different perch height. Habitat use and the variety of items found show P. jubatus as a species that can consume any kind of arthropod available in the strata of the forest where it is foraging.

Ecological patterns of blood-feeding by kissing-bugs (Hemiptera: Reduviidae: Triatominae)

Host use by vectors is important in understanding the transmission of zoonotic diseases, which can affect humans, wildlife and domestic animals. Here, a synthesis of host exploitation patterns by kissing-bugs, vectors of Chagas disease, is presented. For this synthesis, an extensive literature review restricted to feeding sources analysed by precipitin tests was conducted. Modern tools from community ecology and multivariate statistics were used to determine patterns of segregation in host use. Rather than innate preferences for host species, host use by kissing-bugs is influenced by the habitats they colonise. One of the major limitations of studies on kissing-bug foraging has been the exclusive focus on the dominant vector species. We propose that expanding foraging studies to consider the community of vectors will substantially increase the understanding of Chagas disease transmission ecology. Our results indicate that host accessibility is a major factor that shapes the blood-foraging patterns of kissing-bugs. Therefore, from an applied perspective, measures that are directed at disrupting the contact between humans and kissing-bugs, such as housing improvement, are among the most desirable strategies for Chagas disease control.

Trophic interactions among sympatric zooplanktivorous fish species in volume change conditions in a large, shallow, tropical lake

Significant reductions in the water volume of shallow lakes impose a restriction on species segregation promoting more interactions in the trophic relationships. The diets of three closely related zooplanktivorous silversides belonging to the Atherinopsidae species flock of lake Chapala, Mexico, were analyzed at two sites (Chirostoma jordani, C. labarcae, andC. consocium). Diets were described in critical shallow (August 2000) and volume recovery conditions (August 2005). Diets included mainly cladocerans (Bosmina, Ceriodaphnia, and Daphnia) and copepods (Cyclops). A significant difference in diets was detected when comparing years (MRPP analysis, A = 0.22, p < 0.0001) and sites at different years (MRPP analysis, A = 0.17, p = 0.004). According to niche breadth mean values, species were classified as specialized and intermediate feeders. In shallow conditions, the small range of niche breadth (1.72 to 3.64) and high diet overlap values (D = 0.64, L = 8.62) indicated a high potential for interspecific exploitative interaction. When the lake volume recovered, an increase in the niche breadth range (1.04 to 4.96) and low niche overlap values (D = 0.53, L = 2.32) indicated a reduction of the species interaction. The Mann- Whitney U-test supported this pattern by showing a significant difference between years for niche overlap (p = 0.006). The increased interaction during the low volume suggests alternative segregation in life-history variations and other niche dimensions such as spatial or temporal distribution.

La reducción significativa en el volumen de agua de los lagos someros impone una restricción en la segregación de las especies y promueve una mayor interacción en las relaciones tróficas. Se analizó la dieta de tres especies cercanamente emparentadas de zooplanctívoros pertenecientes al flock de Aterinópsidos del lago de Chapala en dos sitios (Chirostoma jordani, C. labarcae y C. consocium). Las dieta fue descrita en una condición somera crítica (Agosto 2000) y en una condición de recuperación del lago (Agosto 2005). En la dieta se incluyen principalmente cladóceros (Bosmina, Ceriodaphnia y Daphnia) y copépodos (Cyclops). Se detectó una diferencia significativa en la dieta cuando se comparan los años (análisis MRPP, A = 0.22, p < 0.0001) y los sitios en los diferentes años (análisis MRPP, A = 0.17, p = 0.004). De acuerdo a los valores promedio de amplitud de nicho, las especies fueron clasificadas como especialistas y consumidores intermediarios. En condiciones someras, el pequeño intervalo de la amplitud de nicho (1.72 a 3.64) y los altos valores del traslape de nicho (D = 0.64, L = 8.62) indicaron un alto potencial para una interacción explotativa inter-específica. Cuando el lago se recupera en su volumen, un incremento en el intervalo de amplitud de nicho (1.04 a 4.96) y los bajos valores del traslape de nicho (D = 0.53, L = 2.32) indicaron una reducción en la interacción de las especies. La prueba U de Mann-Whitney refuerza este patrón al mostrar una diferencia significativa entre los años para el traslape de nicho (p = 0.006). El incremento en la interacción de las especies durante condiciones de volumen bajo, sugiere una segregación alternativa con variaciones en la historia de vida y en otras dimensiones del nicho como en el caso de la distribución espacial y temporal.

Extension of the geographical distribution of two anuran species for Rio Grande do Sul State, Brazil, with comments on natural history / Extensão da distribuição geográfica de duas espécies de anuros para o Estado do Rio Grande do Sul, Brasil, com comentários sobre história natural

We record for the first time Crossodactylus schmidti (Anura: Hylodidae) and Proceratophrys avelinoi (Anura: Cycloramphidae) from Rio Grande do Sul State, Brazil, based on individuals captured in an area of Mesophytic Semideciduous Forest, the Parque Estadual do Turvo, located in the northwest region of the state. These records extend the geographical range for both species in about 60 km from the nearest known locality, the Municipality of San Vicente, Misiones, Argentina. We provide a characterization of the calling site used by males of Crossodactylus schmidti, and we also determined the niche breadth of P. avelinoi regarding to the use of water bodies.

Reportamos o primeiro registro de Crossodactylus schmidti (Anura: Hylodidae) e Proceratophrys avelinoi (Anura: Cycloramphidae) para o Estado do Rio Grande do Sul, Brasil, com base em indivíduos coletados em área de Floresta Estacional Semidecidual, Parque Estadual do Turvo, região noroeste do estado. Estes registros ampliam a área de distribuição das duas espécies em aproximadamente 60 km a partir da localidade mais próxima conhecida, o Município de San Vicente, Misiones, Argentina. Fornecemos, ainda, uma caracterização do sítio de vocalização de C. schmidti e determinamos a amplitude de nicho de P. avelinoi quanto ao uso de corpos d'água.

Interacciones tróficas de las seis especies de peces más abundantes en la pesquería artesanal en dos bahías del Pacífico Central Mexicano

Trophic interactions of the six most abundant fish species in the artisanal fishery in two bays, central Mexican Pacific. We surveyed the trophic components in six species of Bahía de Navidad and Bahía de Chamela: Microlepidotus brevipinnis, Caranx caballus, Haemulon flaviguttatum, Lutjanus guttatus, L. argentiventris and Mulloidichthys dentatus. Two main seasonal periods were considered: 1) North Equatorial Counter Current NECC period influence (T1) and 2) California Current CC period influence (T2). In Bahía de Navidad 78 prey taxa were identified in the stomachs. From July to December (T1), 64 prey taxa were found, and from January to June (T2), 45 prey items. In Bahía de Chamela 93 prey items were identified; 74 during T1 and 60 during T2. The highest prey number was found in the stomachs of M. dentatus during T1 in Bahía de Navidad and the lowest prey number (7) was recorded in H. flaviguttatum in Bahía de Navidad in the same period. Crustaceans were the most frequently recorded prey items, followed by fishes, mollusks, polychaetes, and echinoderms in both seasonal periods and sites. The six fish species studied are considered as specialist feeders due the low values of the niche breadth index. There was little similarity among the diets. Rev. Biol. Trop. 58 (1): 383-397. Epub 2010 March 01.

Se analizaron los componentes tróficos de las seis especies de peces más importantes en la captura de la pesquería artesanal en las Bahía de Navidad y Chamela, ubicadas en la costa de Jalisco, México. Las especies estudiadas fueron Microlepidotus brevipinnis, Caranx caballus, Haemulon flaviguttatum, Lutjanus guttatus, Lutjanus argentiventris y Mulloidichthys dentatus. Se consideraron dos periodos de estudio de acuerdo a las pautas hidroclimáticas y los patrones de producción biológica en la zona: periodo de influencia de la Contracorriente Norecuatorial (T1), y periodo de influencia de la Corriente de California (T2). En Bahía de Navidad se identificaron 78 presas en total para las seis especies. En el periodo comprendido entre julio y diciembre (T1) se identificaron 64 presas y 45 de enero a junio (T2). En Bahía de Chamela se identificaron 93 presas, encontrando 74 presas en el periodo T1 y 60 presas para el periodo T2. El mayor número de presas se encontró en M. dentatus con 34 presas en el periodo T1 de Bahía de Chamela y el menor número fue en H. flaviguttatum en T1 de Bahía de Navidad con solo 7 presas. Los crustáceos fueron las presas de mayor presencia en la dieta, seguidos por peces, moluscos, poliquetos y equinodermos, en ambos periodos y sitios de muestreo. Las seis especies analizadas se consideran como especialistas, dados los bajos valores del índice de amplitud de nicho en ambos periodos y sitios de muestreo.

Comparative feeding ecology and habitats use of Crenicichla species (Perciformes: Cichlidae) in a Venezuelan floodplain river

Feeding behavior and habitat use of two species of pike cichlids, or mataguaros, (Crenicichla lugubris and C. aff. wallacii) were studied in the río Cinaruco, a floodplain river in the Venezuelan llanos. We examined 309 individuals of C. lugubris and 270 individuals of C. aff. wallacii from both the main channel and lagoons throughout the falling-water phase of the annual hydrological cycle. Crenicichla lugubris was common within habitats that contained rocks or woody debris, whereas C. aff. wallacii was more abundant in lagoons than the main channel, especially within shallow areas containing leaf litter. Although we did not capture C. aff. wallacii in rocky shoals, they sometimes were observed in these habitats. Crenicichla lugubris was larger than C. aff. wallacii (198.4 mm and 44.6 mm, respectively). Analysis of stomach contents showed that larger specimens (> 100 mm SL) C. lugubris fed mostly on small fishes (e. g. characids, cichlids), but juveniles (< 100 mm SL) consumed mostly aquatic insects, fish scales, and shrimps. Crenicichla aff. wallacii fed on aquatic insects and other invertebrates associated with leaf litter substrates.

O comportamento alimentar e o uso de habitat de duas espécies de "joanas", ou "mataguaros", (Crenicichla lugubris e C. aff. wallacii) foram estudados no río Cinaruco, uma planície de alagamento nos llanos Venezuelanos. Examinamos 309 indivíduos de C. lugubris e 270 de C. aff. wallacii do canal principal e lagoas ao longo da fase de vazante de um ciclo hidrológico anual. Crenicichla lugubris foi comum em ambientes que continham rochas, galhos e troncos, enquanto que C. aff. wallacii foi mais abundante em lagoas do que no canal principal, especialmente em áreas rasas contendo folhiço. Embora não tenhamos capturado C. aff. wallacii em cardumes em meio às rochas, em algumas ocasiões eles foram observados nestes ambientes. Crenicichla lugubris foi maior do que C. aff. wallacii (198,4 mm e 44,6 mm CP, respectivamente). Análise dos conteúdos estomacais de C. lugubris revelou que os indivíduos maiores (> 100 mm CP) se alimentaram principalmente de peixes pequenos (e. g. caracídeos e ciclídeos), e os menores (< 100 mm CP) consumiram principalmente larvas aquáticas de insetos, escamas de peixes e camarões. Crenicichla aff. wallacii se alimentou de insetos aquáticos e outros invertebrados associados ao folhiço.

Quantitative analysis of the community structure of tropical amphibian assemblages and its significance to conservation.

Amphibian community structure in five tropical sites was studied using dominance, diversity, evenness indices, niche breadth and overlapping scores and association analysis. Ten species of amphibians with average density/ha varying from 8 to 49 in different sites were collected. Rana limnocharis and Bufo melanostictus were respectively the dominant amphibia in paddy fields and other sites. Niche breadth scores indicated Rana limnocharis, Bufo melanostictus and Rana cyanophlyctis as habitat generalists indicating wide tolerance to environmental gradients. Five frog species i.e. Rana tigerina, Microhyla ornata, Ramanella variegata, Uperedon systoma and Polypedates maculatus were considered habitat specialists indicating narrow tolerance to environmental gradients. Niche breadth scores were found to be a function of the cumulative relative abundance value of different species. The niches of Rana limnocharis and Rana cyanophlyctis, Bufo melanostictus and Bufo stomaticus showed maximum overlapping. Rana tigerina showed maximum niche overlapping with Rana variegata in paddy fields and with Microhyla ornata when all sites were taken together. The coefficient of community index was maximum between the paddy fields and minimum between the paddy fields and forest site. Rana tigerina occurred very sparsely and analysis of data indicates that its population are threatened and require conservation measure.