1. Introduction
Earthworms represent an appropriate model for the study of the
immune system of invertebrates. Earthworms, like other invertebrates,
rely generally on the innate immune system, including
both cell-mediated and humoral mechanisms (Cooper et al., 2002).
The body plan of the earthworm is based on a tube-within-tube
concept, with the true coelomic cavity surrounding the gut.
Earthworms are cosmopolitan and can be found in all types of soil
habitats (Edwards and Bohlen, 1996). From the immunological
perspective, soils are perhaps the most complex microbial habitats
comprising the broad spectrum of soil bacteria, algae, fungi and
protists that exhibit almost endless variations in potential