Manipulação e interação parasitária em organismos aquáticos amazônicos: adaptações e estratégias

Abstract

Parasites exploit the host as a habitat or as a source of metabolic resources, depending on it to survive, imposing costs, causing damage, and using, in many cases, manipulative strategies to achieve their success. However, little is known about how parasitic infection/infestation interferes with the individual survival, fitness, and behavior of aquatic organisms in Central Amazonia. In this thesis, we investigated whether two parasites that have complex life cycles influence predator-prey interactions and the life history of their host, the piscivorous fish Acestrorhynchus falcirostris. We also evaluated whether a branchiuran ectoparasite interferes in the life history of tadpoles of Boana geographica, presenting specificity for this host. We performed host and parasite sampling over time, as well as food analysis, histology, fecundity, and energy allocation assessments to better understand the interaction of A. falcirostris with the trematodes Austrodiplostomum compactum and Bellumcorpus majus. Our results demonstrate that fish eyes suffer damage that, in some cases, results in retinal rupture and cataract, which do not interfere with the individuals' well-being; and that the presence of parasites or eye diseases do not interfere with the choice of prey by the fish. When present in the gonads of A. falcirostris, B. majus causes mechanical castration, maybe feeding directly on oocytes, but does not result in a significant decrease in fish fecundity. On the other hand, we performed experiments on survival and parasite specificity to understand the interaction between the tadpoles of B. geographica and the ectoparasite Argulus sp. We observed that Argulus sp. interferes with the life history of tadpoles, affecting growth, foraging, and survival, but not its schooling behaviour. We also found that the tadpoles of B. geographica are apparently the only hosts of Argulus sp. in its natural environment, but in a confined environment, they adhere to alternative hosts, migrating to B. geographica as the days go. We emphasize that the parasite-host interactions are complex, and their understanding can contribute to essential elements for elucidating evolutionary strategies that generate and maintain biodiversity in aquatic environments. However, the possible forms of parasitic manipulation remain poorly understood in the Amazon region, representing one of the greatest frontiers of exploring biological and ecological knowledge in the biome.