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Reduced detrital resources limit Pycnopsyche gentilis (Trichoptera: Limnephilidae) production and growth

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Eggert, Susan L.; Wallace, J. Bruce

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Journal North American Benthol. Society 22(3): 388-400


Leaf inputs in temperate forest streams may limit caddisfly production because leaf detritus serves both as a food and case-material resource. We estimated Pycnopsyche gentilis produdion in a stream experimentally decoupled fmm its riparian habitat and a reference stream for 8 y in the southern Appalachians. We also examined laboratory survivorship, growth, and case-building activities of P. gentilis in substrate containing various quantities of leaf material. Pycnopsyche gentilis produdion declined to 0 within 3 y of the start of litter exclusion. Abundance, biomass, and production of P. gentilis were positively related to leaf litter standing naps. Maxixnum individual length, of P. gentilis was reduced when annual leaf standing crops fell below 25 to 50 g AFDM/m2. Observations of case construction for instars removed from their origninal leaf cases and kept in substrate with low leaf standing crop, showed that P. gentilis was capable of rebuilding a case of available substrate and surviving for 3 to 4 wk before dying of starvation Survivorship and growth were significantly greater for larvae reared at high and intermediate leaf standing crops, than at low leaf standing crop. Older instars had higher survivorship rates but lower growth rates than younger instars in the low litter substrates. Survivorship and growth rates were lower for some individuals forced to rebuild new cases, indicating an energetic cost associated with case-building activities. Our results demonsrate that the linkage between terrestrially derived organic matter and production of a caddisfly shredder was a consequence of food availability.


Case-building behavior; caddisfly; organic matter; macroinvertebrates; stream; resource limitation


Eggert, Susan L.; Wallace, J. Bruce. 2003. Reduced detrital resources limit Pycnopsyche gentilis (Trichoptera: Limnephilidae) production and growth. Journal North American Benthol. Society 22(3): 388-400

Last updated on: October 7, 2016