Efeitos da predação por larvas de Astyanax lacustris (Osteichthyes, Characiformes) em distintos estágios de desenvolvimento sobre as teias alimentares planctônicas.

Abstract

In ecological studies, knowledge of the main factors regulating the growth and survival of fish in early stages of development is essential for the conservation of fishery resources as well as for understanding their trophic relationships and the functioning of various aquatic ecosystems. Thus, studies that seek to understand the trophic interaction between fish larvae and their main prey, as well as their possible effects on the different components of planktonic food webs, especially in tropical environments, where such studies are still scarce, knowledge is incipient. Tested to evaluate the participation of ciliate protozoa, as a food item, in the different stages of development of larvae of Astyanax lacustris, when presented to a natural prey assembly. Thus, we tested the hypothesis that ciliate protozoa would be an important food resource for Astyanax larvae in the early stages of their development, becoming a supplementary resource in more advanced stages, where zooplankton organisms would be the main energy source. The results showed that the ciliates are an important item in the diet of Astyanax larvae, being fundamental for the survival of the larvae in early stages of development and becoming a supplementary resource in later stages when larger organisms such as adult copepods, they are the main resource used by them. The objective was to understand the direct and indirect effects of the predation of the different stages of development of Astyanax larvae on the different zooplanktonic groups, as well as on the structure of the microbial food webs. From this, we tested the hypothesis that larvae of different ages would structure the microbial communities in different ways. The results showed that the different larval ages of Astyanax caused in different configurations of the food webs, affecting strongly the abundance of the zooplankton groups and the flagellates and ciliates protozoa, but having weak effects on the heterotrophic bacterias and picocyanobacterias.