Ingestion and utilization of wood by the larvae of two Trichoptera species, Lasiocephala basalis (Lepidostomatidae) and Lype phaeopa (Psychomyiidae)
Schulte, Ulf; Spänhoff, Bernd; Meyer, Elisabeth I.
published: Oct 24, 2003
ArtNo. ESP141015872002, Price: 29.00 €
Food-intake and digestion of Lasiocephala basalis and Lype phaeopa, both strongly associated with submerged wood, were investigated and compared. Gut-content composition of both taxa was analysed and their capability of digesting cellulose and fungal hyphae was measured by enzyme assays. Gut contents of Lype phaeopa consisted of a significantly higher proportion of wood (88.5% ± 5.8 SD) than those of Lasiocephala basalis (77.8% ± 8.2). The amount of amorphous detritus in the guts was significantly higher in Lasiocephala basalis (16.6% ± 6.9) compared to Lype phaeopa (7.5% ± 3.7). Algae, inorganic material and fungal hyphae were found in comparatively small amounts. Invertebrate remains were detected only in Lasiocephala basalis. To determine the activity of two cellulolytic enzymes, β-D-glucoside glucohydrolase and 1,4-β-D-glucan cellobiohydrolase, substrate-analogues covalently bound to the fluorochrome methylumbelliferyl were used. Cellulose digestion by means of the four mechanisms described by Martin (1991) can be precluded, as 1,4-β-D-glucan cellobiohydrolase was not traceable. Activity of chitobiase could be detected in both species. Therefore, chitin of fungal hyphae might be a potential food resource. Glucohydrolase and chitobiase showed a significantly lower turnover rate with a higher substrate affinity in Lype phaeopa than in Lasiocephala basalis. Different life patterns of the two species are discussed as a reason for these differences. Despite lacking a complete cellulase system in their guts, both taxa may be capable of utilizing cellulose preconditioned by microorganisms. This is supported by results of the gut-content analyses combined with conclusions drawn in a previous study (Schulte et al. 2002).