Aggregation of Lepidostomatidae in small mesh size litter-bags: implication to the leaf litter decomposition process Aung Nanda Æ Takashi Asaeda Æ Takeshi Fujino Æ Kian Siong Æ Takashi Nakajima Received: 17 July 2008 / Accepted: 8 August 2008 / Published online: 24 August 2008 Ó Springer Science+Business Media B.V. 2008 Abstract Invertebrate colonization during leaf litter decomposition was studied at the 2nd order of Yanase River, Iruma city, Saitama, Japan from November 13, 2002 to May 20, 2003. Two different mesh sizes (1 and 5 mm) of litter-bags were used to evaluate the decom- position of leaf litter of Sakura (Prunus lannesiana), bags were placed equally in riffle (water flow velocity: 0.2–0.6 m s -1 ) and pool (water flow velocity: 0.04– 0.06 m s -1 ). Mass loss and invertebrates in the litter- bags were monitored at interval between 1 and 3 weeks, and the invertebrates were classified based on their functional feeding group. Among the inverte- brates found inside the litter-bags, the case-bearing shredder Lepidostomatidae was the most dominant invertebrates and they were the early colonizer that appeared about 3 months after the litter-bags immer- sion. In absence or low number of leaf-shredders, the decomposition rates in 1 and 5 mm litter mesh bags followed the exponential (or first-order) decay kinetic (R 2 : 0.72–0.92). However, the presence of a large number of leaf-shredders in 1 mm litter-bags caused an acceleration of decomposition process; that even resulted faster mass loss than the loss from the 5 mm mesh bags placed in riffle area (0.030 day -1 vs. 0.011 day -1 ). Our results shows the importance of using different mesh sizes of litter-bags in decompo- sition study, which is applicable to the experiment in lotic or lentic ecosystem. Using smaller mesh size of litter-bags can provide information on how significant the effect of detritus feeders on the decomposition process, while the bigger mesh size can represent better the natural decomposition process when a large number detritus feeders is present in the smaller mesh size of litter-bags. Keywords Detritivore Á Decomposition Á Litter-bag Á Lepidostomatidae Á Shredder assemblage Introduction The decomposition of detritus (i.e. leaves, twigs, and woody parts) plays important role in the processes of energy flow and nutrient cycling (Giller and Malmq- vist 1998). Litter-bag decomposition studies in lotic and lentic ecosystem usually employ mesh bags with 0.8–10 mm mesh size, the use of smaller-mesh bags universally results in reports of slower decomposition rates for the same material and this has been attributed both to exclusion of detritus feeders from the smaller mesh and to greater loss by fragmentation in larger-mesh bags (Brinson et al. 1981). Several ecologists have also used few mesh sizes of litter mesh bag in order to achieve their research objec- tives. For example, Watts et al. (2008) used 0.1 mm A. Nanda Á T. Asaeda (&) Á T. Fujino Á K. Siong Á T. Nakajima Department of Environmental Science, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama 338-8570, Japan e-mail: asaeda@mail.saitama-u.ac.jp 123 Wetlands Ecol Manage (2009) 17:417–421 DOI 10.1007/s11273-008-9114-6