Spatial, seasonal and ontogenetic variation in the diet of Astyanax aff. fasciatus (Ostariophysi: Characidae) in an Atlantic Forest river, Southern Brazil

Abstract

This study described the feeding habits of the characin Astyanax aff. fasciatus. The diet compositions of specimens from two sites (A and B) on a river in Southern Brazil were compared according to the size of individuals and seasonal period. The collections were performed monthly from March 2005 to February 2006, where the stomach contents of 290 specimens were assessed. Food items for A. aff. fasciatus were basically composed of plants and insects, especially leaf fragments, seeds, fruits, filamentous algae, aquatic and terrestrial insects and insect fragments. At site A, the most common items were insect and plant fragments. Conversely at site B, plant fragments were more representative. In general, all items of animal origin showed the highest feeding index values at site A, whereas at site B detritus and grass items were more abundant. The composition of items varied seasonally, with higher diversity of items being recorded during the spring at both sites. Smaller individuals preferred items of animal origin, while the larger ones consumed mainly items of plant origin. According to its size, A. aff. fasciatus in this study may be considered a species with insectivorous tendencies when immature or herbivorous tendencies when adult. Nevertheless, its feeding habits may be flexible according to resource availability, showing wide ontogenetic, besides spatial and temporal variation.Este estudo descreveu os hábitos alimentares do lambari Astyanax aff. fasciatus. Foram comparadas as composições alimentares de espécimes de dois sítios (A e B) de um rio no sul do Brasil de acordo com o tamanho dos indivíduos e do período sazonal. As coletas foram realizadas mensalmente de março de 2005 a fevereiro de 2006, sendo o conteúdo estomacal de 290 exemplares analisado. A dieta de A. aff. fasciatus foi composta basicamente por plantas e insetos, especialmente fragmentos de folhas, sementes, frutos, algas filamentosas, insetos aquáticos e terrestres e fragmentos de insetos. No sítio A, os itens de maior importância foram fragmentos de insetos e plantas. Ao contrário no sítio B, fragmentos de plantas foram mais representativos. Em geral, todos os itens de origem animal apresentaram os maiores valores do índice alimentar no sítio A, enquanto que no sítio B detritos e gramíneas foram mais abundantes. A composição dos itens ingeridos variou sazonalmente, sendo a maior diversidade registrada durante o período da primavera para ambos os sítios. Indivíduos pequenos preferiram itens de origem animal enquanto que os maiores consumiram principalmente itens de origem vegetal. De acordo com seu tamanho A. aff. fasciatus neste estudo pode ser considerada uma espécie com tendências à insetivoria quando imaturo, ou à herbivoria quando adulto. No entanto, seu hábito alimentar pode ser flexível de acordo com a disponibilidade de recursos, mostrando ampla variação tanto ontogenética quanto espacial e temporal.

Plasticity in the diet of Astyanax taeniatus in a coastal stream from south-east Brazil

“…In the Mato Grosso stream Astyanax taeniatus had a varied diet. Distinct feeding behaviour with high plasticity has been previously described for this genus (Costa, 1987;Cassemiro et al, 2002;Gomiero and Braga, 2003;Borba et al, 2008;Wolff et al, 2009). In this study, and in another by Bennemann et al (2005), the diet of Astyanax species was found to consist primarily of allochthonous insects and terrestrial plant debris, and changes in the consumption of these resources were related to physical changes in the environment.…”

“…This is also seen in other species of the Characidae family (e.g. Barreto and Aranha, 2006;Wolff et al, 2009;Mazzoni et al, 2010a), indicating that the relationship between intestine length and the standard length of a species varies during the growth of an individual (Mazzoni et al, 2010a). The intestinal quotient (Qi) can be a useful tool for evaluating ontogenetic variations in the diet of fish (Zavala-Camim, 1996), and an increase in the intestinal quotient of adults may be associated with high plasticity, the capacity for food spectrum expansion (Andrian et al, 2001) and the utilization of less digestible (e.g.…”

Fish fauna in forested and rural streams from an ecoregion of high endemism, lower Iguaçu River basin, Brazil

“…This high similarity between local and broader spatial distributions could be explained by: i) lacking larger migratory species in Iguaçu River basin that are deeper channel dwellers in the Paraná River and others tributaries (Agostinho et al 2003(Agostinho et al , 2008; ii) the wide ability of the characins of genus Astyanax to colonize practically all environments of basin, including large and small inland water or even reservoirs. This genus present broad distribution in low Iguaçu River basin (Garavello & Sampaio 2010), pronounced trophic plasticity (Wolff et al 2009, and were captured here, with high abundances in all streams independently of physiographic features and land use.…”

Contrasting feeding habits of post-larval and adult Astyanax cavefish

“…Such is the case for surface Astyanax. A surface population studied by Wolff et al (2009) showed that in fish of less than 5 cm standard length, 75.8% of their diet by volume was made of animal items. In 5.1 to 7.5 cm long fish, animal content decreased to 28.6%, and when longer than 7.6 cm, its animal derived diet was reduced to 20.7% to the increase of plant items.…”