Original paper

Life history patterns and dietary changes of several caddisfly (Trichoptera) species in a northern Spain stream

Basaguren, A.; Riano, P.; Pozo, J.

Abstract

Life history patterns of Lepidostoma hirtum, Sericostoma selysii, Hydropsyche pellucidula and Hydropsyche siltalai were investigated for a year in the Agüera stream (northern Spain). All four species showed univoltine life cycles, low synchronisation of larval development, and extended periods of hatching and flight. Young larvae of all four species showed a quick development from summer to autumn probably due to favourable climatic and hydrological conditions. High flows in winter and spring reduced densities presumably by drift. Additionally, food habits of these species, plus those of large individuals of Potamophylax latipennis, Rhyacophila relicta, R. denticulata and R. eatoni were examined. Gut contents indicated changes in diets with development in the four species whose life history was determined. In general, fine detritus was the main food component for early instars, while other food types increased in importance in more developed instars. L. hirtum and S. selysii showed mainly a detritivorous trophic character, their diet shifting from fine detritus in early instars to coarse detritus in late ones. Coarse material in L. hirtum guts increased from 0 % at first to 74 % at IVth instar, and in S. selysii from 48 % at first to 95 % at VIIth instar. The hydropsychids H. pellucidula and H. siltalai showed a varied diet, dominated by fine detritus in early instars, but incorporating more than 25 % of animal material in late instars. Large individuals of P. latipennis fed mainly on coarse detritus (95.8 % of the diet). R. relicta and R. denticulata late instars showed a carnivorous diet, with up to 75 % of animal material. On the other hand, with 51.4 % of fine detritus, 30.8 % of animal material and 15 % of coarse plant detritus, R. eatoni seemed to be more omnivorous. Chironomids and baetids were the most frequent prey items in Hydropsyche and Rhyacophila guts. All these results indicate the generalist feature of most studied species from a trophic point of view.

Keywords

Caddisflies speciesHydropsychelife cyclegut contentsdiet shiftdevelopment