Poster Presentations

Session Title: The Animal Microbiome
Presentation Date: Monday, August 18, 2008
Poster Board Number: 0392

GUT BACTERIAL COMMUNITIES REFLECT THE FEEDING HABITS OF EARTHWORMS

D. Thakuria, D. Finan, O. Schmidt, D. Egan, F. M. Doohan
University College Dublin, UCD School of Biology and Environmental Science, Dublin, Ireland

Associations between the gut bacterial communities and earthworms (Lumbricidae) species are poorly understood. We assessed the gut bacterial communities of the earthworm species Aporrectodea caliginosa, A. longa, A. limicola, Lumbricus terrestris and L. friendi and soil samples collected from a permanent pasture-clover field and an adjacent conventional maize monocrop field. We determined bacterial community composition using automated ribosomal intergenic spacer analysis (ARISA) fingerprinting. Bacterial ribotype numbers and diversity (Margalef's richness, Pielou's evenness and Shannon's diversity) indices in soils were significantly higher than in the gut content of any of the earthworm species (P < 0.01, analysis of variance). Hierarchical clustering with group-average linking and non-metric multi-dimensional scaling ordination based on Bray-Curtis similarity matrices of bacterial ARISA (abundance) profiles revealed that the bacterial community compositions within soils and the gut contents of A. caliginosa and A. longa were significantly different from those within the gut contents of L. terrestris, L. friendi and A. limicola (Global R=0.994 and 0.953 for maize monocrop field and pasture-clover field, respectively; 999 permutations and P< 0.001, analysis of similarity). This study confirmed that the bacterial community composition of the soil-feeding (endogeic) A. caliginosa is more similar to soils than that of the litter-feeding (anecic) L. terrestris and L. friendi. The ecological grouping of A. longa is not well-defined, but our results support the theory that this species exhibits an endogeic feeding behaviour.