The importance of protists as a food resource for Astyanax lacustris (Osteichthyes, Characiformes) larvae at different stages of development

Investigating the main factors regulating the growth and survival of fish in early stages of development is essential for the understanding of their trophic relationships. Most fish larvae are active planktonic predators which feed on motile prey and their success in foraging is influenced by several factors, such as the availability of suitable prey. We aimed to investigate the role of ciliate protists as a food resource in the different stages of development of fish larvae of Astyanax lacustris , when presented to a natural prey assembly. Our results show, through an experimental approach, that ciliate protists are an important item in A. lacustris larvae diet, especially in the early stages of their development, becoming an additional resource in more advanced stages, when A. lacustris larvae change their food preference, selecting larger food items such as adult copepods.