Feeding spectra and activity of the freshwater crab Trichodactylus kensleyi (Decapoda: Brachyura: Trichodactylidae) at La Plata basin

Verónica Williner,Debora Azevedo Carvalho,Pablo A Collins

doi:10.1186/s40555-014-0071-x

Abstract

BackgroundIn inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. The aim of this study is to analyze the natural diet of Trichodactylus kensleyi of subtropical rainforest streams and corroborate the temporal variation in the trophic activity during day hours.ResultsA total of 15 major taxonomic groups were recognized in gut contents. The index of relative importance identified the following main prey items in decreasing order of importance: vegetal remains, oligochaetes, chironomid larvae, and algae. A significant difference was found in the amount of full stomachs during day hours showing a less trophic activity at midday and afternoon. The index of relative importance values evidenced the consumption of different prey according to day moments. Results of the gut content indicate that T. kensleyi is an omnivorous crab like other trichodactylid species. Opportunistic behavior is revealed by the ingestion of organisms abundant in streams such as oligochaetes and chironomid larvae. The consumption of allochthonous plant debris shows the importance of this crab as shredder in subtropical streams. However, the effective assimilation of plant matter is yet unknown in trichodactylid crabs.ConclusionsThis research provides knowledge that complements previous studies about trophic relationships of trichodactylid crabs and supported the importance of T. kensleyi in the transference of energy and matter from benthic community and riparian sources to superior trophic levels using both macro- and microfauna.

Highlights

In inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments
Capture records of this freshwater crab in Argentina range from 200 to 600 m above sea level in streams of subtropical rainforest, where they can be trapped in the bottom under rocks, clay, and sand (Collins 2005)
Trophic ecology studies on trichodactylid crabs in Argentina have reported a variety of aquatic environments and feeding habits (Williner and Collins 2002; Collins et al 2006; Collins et al 2007; Williner and Collins 2013; Carvalho et al 2013a, 2013b)

Summary

Introduction

It is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. Trichodactylus kensleyi has a geographical distribution associated to the Paraná and Uruguay Rivers and restricted to the subtropical forest of Argentina, Paraguay, Brazil, and Uruguay (Magalhães 2003) Capture records of this freshwater crab in Argentina range from 200 to 600 m above sea level in streams of subtropical rainforest, where they can be trapped in the bottom under rocks, clay, and sand (Collins 2005). Trophic ecology studies (e.g., behavior, feeding habits) on trichodactylid crabs in Argentina have reported a variety of aquatic environments (e.g., in subtropical savannah and alluvial valley of template rivers) and feeding habits (Williner and Collins 2002; Collins et al 2006; Collins et al 2007; Williner and Collins 2013; Carvalho et al 2013a, 2013b) These crustaceans are omnivorous with a wide trophic spectrum that ranges from algae and plant remains to insect larvae and even vertebrates (Collins et al 2006). They are prey of many vertebrates like fishes, amphibians, reptiles, birds, and mammals (Bonetto et al 1963; Beltzer 1983; 1984; Beltzer and Paporello 1984; Lajmanovich and Beltzer 1993; Massoia 1976; Bianchini and Delupi 1993; López et al 2005), emphasizing the importance of this species in aquatic systems

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