Untitled

Abstract

The role of adult faeces in juvenile nutrition of two isopod species, Proasellus coxalis s.l. and Asellus aquaticus (L.), with similar trophic strategies and different reproductive output, has been studied in laboratory. Our aim was to consider the possible competitive mechanisms occurring at the beginning of the species coexistence using allopatric populations in single and mixed species experiments. Two series of competition experiments were performed. In the first, adult specimens were used for breeding and feeding trials. Both population dynamics and the percentage of ovigerous females and juveniles were evaluated during 10 months. Adult densities and juvenile percentage of A.aquaticus were lower in the presence of P. coxalis s.l. than when alone. At the end of the breeding experiments the dietary preferences of adults on a set of fungally conditioned leaf discs were not different among treatments. In the second series of experiments, the influence of coexistence on the feeding rates of young asellids and the relative importance of faeces and decaying plant material in their diet were investigated. Individual consumption by wild juveniles in multiple-choice laboratory experiments was measured by radioisotopes ( 32 P). Juveniles of P. coxalis s.l. showed the highest ingestion rates. In co-occurrence, contrary to A.aquaticus, they were able to further increase feeding on parental faeces. The role of parental faeces in the diet of the two species juveniles and the competitive dominance of P. coxalis s.l. are discussed.

The role of alien fish (the centrarchidMicropterus salmoides)in lake food webs highlighted by stable isotope analysis

“…The results are reported as g of ash-free dry organic matter per 100 g dry weight of sediment (AFDM%) and are considered indicative of the overall basal resource availability for detritivorous invertebrates Calizza et al, 2012;Costantini & Rossi, 1998;di Lascio et al, 2013;Rossi et al, 2015). In addition, the ash-free dry organic matter content in the first 10 cm of sediment was assessed after muffle combustion (5 hr at 500°C) .…”

“…In addition, the ash-free dry organic matter content in the first 10 cm of sediment was assessed after muffle combustion (5 hr at 500°C) . The results are reported as g of ash-free dry organic matter per 100 g dry weight of sediment (AFDM%) and are considered indicative of the overall basal resource availability for detritivorous invertebrates Calizza et al, 2012;Costantini & Rossi, 1998;di Lascio et al, 2013;Rossi et al, 2015).…”

Distribution, identification and range expansion of the common Asellidae in Northern Europe, featuring the first record of Proasellus meridianus in the Nordic countries

“…Fano (1974) added that in polluted waters the species P. coxalis probably had a greater adaptive capacity than A. aquaticus. Costantini & Rossi (1998) also found P. coxalis to be ecologically dominant under laboratory conditions. important role as vectors in their dispersal.…”

Combined effects of acidification and competition on the feeding preference of a freshwater macroinvertebrate, Asellus aquaticus (Crustacea:Isopoda): a laboratory experiment

“…The acute effects of low pH on juveniles and brooding females have been demonstrated in laboratory toxicity tests (Naylor et al 1990). It is also known in central Italy that A. aquaticus is affected by competition from Proasellus coxalis sensu lato, a closely related species, which reduces A. aquaticus recruitment (Rossi et al 1983a(Rossi et al , 1983bCostantini and Rossi 1998). Thus we designed a laboratory study to answer the following main questions: (1) does medium-term sublethal acidification affect the feeding rate and strategy of non-brooding A. aquaticus adults?…”