Growth of Two Stream Caddisflies (Trichoptera) on Leaves Colonized by Different Fungal Species

Abstract

We examined the food quality of different fungi by determining growth, consumption and survivorship of two caddisflies fed diets of aspen leaves colonized by single fungal species. Mid-to-late fifth instar larvae of Hesperophylax magnus grew better on leaves colonized by Alatospora acuminata, Flagellospora curvula or Tetracladium marchalianum than on leaves colonized by Lemonniera aquatica or on stream detritus, but differences in instantaneous growth rates on these diets were not statistically significant. For early fifth instar larvae of Psychoglypha sp., we detected statistically significant differences in instantaneous growth rates on the following diets: F. curvula = A. acuminata > Heliscus lugdunensis = Articulospora inflata > L. aquatica = stream detritus. Psychoglypha sp. larvae also exhibited high survivorship on these diets through 20 d, but experienced 100% mortality when fed leaves colonized by Filosporella annelidica or T. marchalianum. Psychoglypha sp. larvae grew significantly faster on aspen leaves fully conditioned (10 d and 20 d) by F. curvula and H. lugdunensis than on preconditioned leaves (4 d). For both caddisflies, consumption rates were higher on diets that supported higher growth rates. Food quality of all four fungi in the Hesperophylax experiment and four of the seven fungi in the Psychoglypha experiment corresponded well with caddisfly preferences we have previously determined. Food quality was affected by fungal species and conditioning time. However, even well-conditioned leaves did not support high growth rates in caddisflies if the leaves were colonized by low quality fungi.