Influence of Trichodactylus fluviatilis on Leaf Breakdown in Streams: Understanding the Role of Freshwater Crabs in Detritus-based Food Webs.

Abstract

Larissa Costa, Walace Kiffer Jr., Cinthia Casotti, Juliana Rangel, and Marcelo Moretti (2016) Freshwater crabs can affect leaf breakdown by consuming leaves or invertebrate shredders. The aims of this study were to analyze the gut content of Trichodactylus fluviatilis and evaluate the influence of this macroconsumer on leaf breakdown. For this, we (i) performed gut analyses of 55 individuals of T. fluviatilis and (ii) determined leaf decay rates and FPOM production in laboratory trials containing crabs and the caddisfly shredder Triplectides sp., alone and together, and leaves differing in quality. We hypothesized that T. fluviatilis feeds both on leaves and Triplectides sp. and, consequently, leaf decay rates would be lower when these organisms were together. The main food categories in T. fluviatilis guts were algae and FPOM, while CPOM and animal tissue were rare. Leaf decay rates and FPOM production did not differ across shredder treatments or leaf species. However, the survival of Triplectides sp. was higher when alone. The results support the potential for participation of T. fluviatilis in leaf breakdown and demonstrated that, in spite of the high abundances of algae and FPOM in the gut content, adults of this species have the potential to feed both on leaf litter and larvae of Triplectides sp. However, the hypothesis of this study was only partially corroborated because decay rates did not change across treatments.