Effect of detritus quality and temperature on the activity of fragmentation Phylloicus sp.

Fernanda Keley Silva Pereira Navarro, José Francisco Gonçalves Júnior


Leaf decomposition in lotic ecosystems involves physical abrasion, microbial conditioning and fragmentation by invertebrate shredders. The attractiveness of a given leaf detritus to invertebrates depends on the chemical composition, physical structure, stage of microbial colonization and degradation level of the detritus. In addition to the quality of leaf debris, water temperature also affects organic matter cycling in aquatic environments. In this context, the objectives of this study were: i) to increase knowledge about the role of invertebrate shredders on fragmenting senescent, conditioned senescent and green leaves of Richeria grandis under gradual temperature rise and check the possible consequences on leaf mass loss; ii) to verify the preference of Phylloicus spn. for leaves for the production of larval case.The experiment I consisted of three treatments with different water temperatures: Treatment 1: 20oC, Treatment 2: 24oC, Treatment 3: 28oC. Each aquarium (60L) was provided with 20 leaf discs (10 discs of senescent leaves and 10 discs of conditioned senescent leaves) of R. grandis. In the experiment II, we added 10 discs of green leaves of R. grandis and 2 invertebrates (Phylloicus sp.) to each aquarium. Leaf mass loss in the presence or absence of fragmentation was not significantly influenced by the intraspecific quality of the detritus and temperature. Intraspecific quality of resources mixed with green leaves can lead to increased contact of phenolic content on senescent leaves, leading to a similarity in food exploitation by invertebrates. However, the production of larval cases by Phylloicus sp. seems to be dependent on the resistance presented by the resource rather than the phenolic content, thus leading shredders to use the senescent debris in greater amounts, regardless of temperature.

Iheringia Série Zoologia

Museu de Ciências Naturais, Fundação Zoobotânica do Rio Grande do Sul

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