Factors Affecting Leaf Litter Decomposition by Micropterna sequax (Trichoptera: Limnephilidae)

Abstract

Feeding behaviour and consumption rates of the caddisfly Micropterna sequax (Trichoptera: Limnephilidae) larvae were investigated under laboratory conditions. The consumption rates of M. sequax were measured at four temperatures (5.5, 9.5, 13 and 19 °C) and its feeding preferences among four leaf species (European beech, oak, chestnut and oriental plane) were studied. Furthermore, fresh and senescent conditioned or not beech leaves were offered to Micropterna larvae to assess the impact of the leaf age and conditioning on the larvae feeding rates. Temperature exerted a pronounced effect on the consumption rates of the larvae, the optimum temperature for feeding being 13 °C. In all the experiments, larvae showed a sound preference for chestnut leaves over the other leaves tested, with consumption rates of up to 0.55 mg leaf mg -1 animal d -1. Senescent beech leaves were clearly preferred against fresh ones, while no significant differences were recorded between the consumption rates of conditioned and non-conditioned plant material. The role of physical and chemical characteristics of the leaves possibly involved in the larvae selectivity is also discussed. IntroductionLeaf litter decomposition is a keystone biological process in mountainous streams, where autotrophic production is reduced due to shading and the main energy source for the stream biota and functioning is provided by the shed leaves of riparian trees (CUMMINS et al., 1989;WALLACE et al., 1999). Aquatic macroinvertebrate shredders play an essential role in the leaf litter breakdown in streams (WALLACE and WEBSTER, 1996;GRAÇA, 2001). Due to the feeding activities of shredders and the physical fragmentation of the leaves, the organic matter of the litter is incorporated into secondary production and large amounts of fine particulate organic matter are generated and consumed by other groups of aquatic organisms (COVICH et al., 1999;GESSNER et al., 1999;GRAÇA and CANHOTO, 2006).The litter input in mountainous streams primarily depends on the riparian vegetation and is composed from leaves from diverse plant species with different physical and chemical properties (KILLINGBECK, 1996). Many studies have shown that shredders prefer to feed on (NOLEN and PEARSON, 1993;FRIBERG and JACOBSEN, 1999;GRAÇA, 2001; RINCÓN and MARTINEZ, 2006). This selective feeding of shredders has been attributed to an array of factors including the nutrient content of the plant material (OSTROFSKY, 1997), its hardness (GRAÇA and ZIMMER, 2005) as well as the presence of plant secondary compounds that make the leaves more or less attractive (GRAÇA, 2001). Water temperature has been also shown to affect the feeding behaviour and the consumption rates of the shredders, as it is a significant determinant of their metabolism (BUZBY and PERRY, 2000;GONZÁLEZ and GRAÇA, 2003). Likewise, 'conditioning' is another important factor determining food preference patterns, with shredders usually showing preference for conditioned over non-conditioned leaves (GRAÇA, 1993;CHUNG and SUBERKRO...

Warming, and the presence of a dominant shredder, drive variation in decomposer communities in a mountain stream

“…displacement towards the poles or higher altitude; Parmesan and Yohe 2003;Walther 2010) and the physiology of individuals (e.g. increased metabolism; Brown et al 2004;Rumbos et al 2010). Such changes are likely to alter the strength and the type of species interactions (Gilman et al 2010): spatial mismatches between species (Stenseth and Mysterud 2002;Schweiger et al 2008), increases in predation rates in response to higher energy requirements (Gotthard 2000), increases in herbivory and pathogenicity (Roy et al 2004), changes in the size of food webs (Petchey et al 1999), and shifts in species dominance (Tylianakis et al 2008;Traill et al 2010) are some of the known consequences of global warming.…”

Biotic interactions enhance survival and fitness in the caddisfly Micropterna sequax (Trichoptera: Limnephilidae)

“…Even though both species appear to be very similar in their functional traits (Higler, 2005;Graf et al, 2015) they showed species-specific responses. It is known that M. sequax is a specialized species when it comes to substrate preference (Rumbos et al, 2010) but unfortunately there is no literature on preferred food particle size.…”

Effect of Bt toxin Cry1Ab on two freshwater caddisfly shredders – an attempt to establish dose-effect relationships through food-spiking

“…were employed as model species (supported by own yet unpublished data). Their selection is motivated by a wide distribution throughout Europe [14][15][16][17][18][19] and their contribution to leaf litter decomposition 20,21 . Mortality, consumption, growth (case width), and larval instars (head capsule width) were recorded as response variables over a study duration of up to 12 weeks.…”