Segregação alimentar entre duas espécies de Heptapteridae no Rio Macaé, RJ

Abstract

BRAZIL-SOUSA, C., MARQUES, R.M. & ALBRECHT, M.P. Food partitioning between two heptapterid fish species in Macaé River, RJ (Southeastern Brazil). Biota Neotrop. 9(3): http://www.biotaneotropica.org. br/v9n3/en/abstract?article+bn00309032009. Abstract:Food is the main axis of niche partitioning among fishes, being an important factor for the organization of their populations. We herein investigate this premise for two closely related species, by characterization and comparison of the natural diet of two heptapterid fishes, Rhamdioglanis transfasciatus and Rhamdia quelen along the Macaé River, Rio de Janeiro state, Southeastern Brazil. R. quelen was classified as carnivore, and the most important items of its diet were crustaceans and fishes. R. transfasciatus was classified as invertivore, as it ate mainly trichopteran and dipteran larvae. The calculation of the trophic position algorithm showed that both species are secondary consumers, but R. quelen had a slightly higher value. Both species can be considered as generalists but with differences of feeding strategies: some individuals of R. quelen behave as specialists, whereas most individuals of R. transfasciatus population act as generalists. Intraspecific comparisons revealed a similar diet of each species between the two sampling sites, however, the niche overlap between the populations of the two species was very low in the sites where both occurred, indicating the existence of resource partitioning between Rhamdia quelen e Rhamdioglanis transfasciatus in Macaé river. Resumo: Alimento é considerado o principal eixo da partilha de nicho entre peixes, sendo um fator importante para a organização de suas populações. Com o intuito de investigar essa assertiva para duas espécies filogeneticamente próximas, a dieta natural de dois peixes da família Heptapteridae, Rhamdioglanis transfasciatus e Rhamdia quelen foi caracterizada e comparada ao longo do curso longitudinal do rio Macaé. R. quelen foi classificada como carnívora, sendo crustáceos e peixes os itens mais importantes da sua dieta, ao passo que R. transfasciatus foi considerada invertívora, tendo consumido principalmente larvas de Trichoptera e de Diptera. A posição trófica calculada revelou que ambas as espécies são consumidoras secundárias, com valores um pouco maiores para R. quelen. As espécies podem ser consideradas generalistas, mas com algumas diferenças na estratégia alimentar adotada por suas populações: alguns grupos de indivíduos de R. quelen se comportaram de forma especialista, enquanto que a população de R. transfasciatus se comporta de forma generalista em sua maioria. Na comparação intraespecífica, a dieta de ambas foi muito semelhante entre as duas localidades, porém a sobreposição de nicho entre as populações das duas espécies foi quase nula nos locais de coocorrência, indicando a existência de partilha alimentar entre Rhamdia quelen e Rhamdioglanis transfasciatus no rio Macaé. Palavras-chave: alimentação, nicho, partilha de recursos, Rhamdioglanis transfasciatus, Rhamdia quelen.

Resource partitioning and ecomorphological variation in two syntopic species of Lebiasinidae (Characiformes) in an Amazonian stream

“…Since the niche is multidimensional, resource partitioning may be not experienced in the type of consumed preys, but in other dimensions like prey size, different use of space and/ or phenotypic characteristics that allow subtle differences in the use of available resources (Esteves and Aranha 1999;Piorski et al 2005;Brazil-Sousa et al 2009). Furthermore, when considering average values of resource use within a population we ignore the fact that the individuals composing the same population may use different resources, minimizing an apparent competition between species.…”

“…Resource partitioning in neotropical fish communities has been well documented (Corrêa et al 2009;Silva et al 2012) and often related to ecomorphological and/ or behavioral differences that influence the use of space (micro-habitat) and food resources (Piorski et al 2005;Lima et al 2008;Brazil-Sousa et al 2009). Morphological features might be indicators of species life habits, types of resource use or adaptations to occupy the environment (Gatz 1979).…”

“…Thus, it can be expected that these species, especially when syntopic, exhibit differences in resource use that might minimize competition (Herder and Freyhof 2006). For example, in the size of consumed prey, use of microhabitats and feeding strategy (Esteves and Aranha 1999;Piorski et al 2005;Brazil-Sousa et al 2009). …”

Differences in the feeding of Rhamdia quelen (Siluriformes, Heptapteridae) in four distinct lotic systems

“…Casatti (2002), by studying this species in a first order stream (São Carlos Stream) registered a high consummation of Araneae, Hymenoptera, some vegetal and Trichoptera and On the other hand, in larger aquatic systems the species uses to consume in a higher importance autochthonous items. Brasil-Sousa et al (2009) found in a 6 th order river (Macaé river) a consume based predominantly on autochthonous items, mainly formed by crustaceans and fish, and defined R. quelen as a carnivorous species specialized for crustaceans and fish in higher amount, followed by other items in a lesser importance (53 items).…”

“…So, it may be difficult to classify the species other to a generalist feeder (Brasil-Sousa et al, 2009). Such a plasticity may be an expected fact, as the normal instability of the freshwater systems may preserve the species which have developed a means of survival within such lotic systems by adapting to distinct food resources (Lowe-McConnell, 1999), a commonly observed fact among the neotropical fishes (Gerking, 1994).…”