Food Related Adaptations in Stream Living Caddisfly Larvae Feeding on Leaves

Abstract

From the 9 most common caddisfly shredders [Sericostoma personatum, Limnephilus centralis, Potamophylax cingulatus, P. nigricornis, Micropterna lateralis, M. sequax, Halesus digitatus, H. radiatus and Chaetopteryx villosa] in a south Swedish stream, 5 were most abundant in the uppermost section. Here bottom surface available to the larvae per a 100 m stream section was about 80 m2 compared to 30 m2 further downstream. Input of allochthonous food material per surface unit was highest in the uppermost section, as was the retention capacity. Life cycle adaptations making effective use of the annual food supply in the form of relatively big larvae present during autumn were pronounced in the upper section. Probably this big best strategy together with very bad food conditions from winter selects for early flight periods. Burrowed pupae as a security to drought were common in the upstream species. Because of the low temperature regime in the uppermost section, food was more effectively used for growth here than further downstream. In lotic larvae a low propensity to leave a food patch as contrasted to lentic larvae was assumed to be due to long distances (high costs) between food patches in streams.