Trophic diversity of idoteids (Crustacea, Isopoda) inhabiting the Posidonia oceanica litter

Abstract

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed that there were considerable inter-and intra-specific differences in diet composition. Diet differed between juveniles and adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the same biotope.

Seagrass organic matter transfer in Posidonia oceanica macrophytodetritus accumulations

“…second-order predators. Few species display a more plant-based diet such as the isopod Idotea balthica, in agreement with a previous study focusing on idoteids of P. oceanica litter(Sturaro et al, 2010). Nevertheless, this is one species whose gut contents and stable isotopes are not in agreement.…”

Meiofauna and harpacticoid copepods in different habitats of a Mediterranean seagrass meadow

“…These consumers are likely to be crucial for the degradation and transport of organic matter to higher trophic levels. For example, macrofauna (juvenile fish prey) is known to ingest detritus with their associated epiphytes and microbial communities (Romero et al , 1992; Vizzini et al , 2002; Mateo et al , 2003; Lepoint et al , 2006; Sturaro et al , 2010). As such, seagrass ecosystems hold a significant fraction of autotrophic biomass (Duarte et al , 2005) that is passed indirectly to higher trophic levels.…”

Decomposition rate and invertebrate colonization of seagrass detritus along a hydrodynamic gradient in a Mediterranean coastal basin: The Stagnone di Marsala (Italy) case study

“…Within the amphipods, the Gammarus genus is a highly opportunistic group (defined as a facultative shredder by Cummins & Klug, ), but with a certain degree of selectivity probably related to environmental characteristics (Friberg & Jacobsen, ; Mancinelli & Rossi, ). Based on stable isotope and/or gut content analysis, some species were reported to directly feed on P. oceanica leaf litter, among the others, the amphipods G. aequicauda and Gammarella fucicola (Remy et al, ) , but also isopods of the genera Idotea and Cleantis (Lepoint et al, ; Sturaro, Caut, Gobert, Bouquegneau, & Lepoint, ) and some echinoderms as the holothurian Holothuria tubulosa Gmelin (Costa, Mazzola, & Vizzini, ). In particular, G. aequicauda relied up to 80% of its diet on P. oceanica leaf detritus (Michel et al, ; Remy et al, ), highlighting the crucial role of this species not only during the fragmentation of the seagrass detritus but also in the transfer of detritus organic matter along the food chain.…”