Amino acid contents were studied in eight earthworm species (Lumbricus rubellus, L. terrestris, Nicodrilus roseus, N. caliginosus, Dendrobaena octaedra, Eisenia nordenskioldi, Octolasium lacteum, Drawida ghilarovi), plant litter and soil. There are considerable differences in the content of essential amino acids between earthworms and their food (for most amino acids, one order of magnitude; for methionine, up to two orders of magnitude). Methionine stores in litter are lower than in earthworm biomass. Flows of essential amino acids through earthworm populations with consumed plant residues and soil are only three times higher than their content in the biomass, except methionine. The flow of methionine is only half its content in the biomass. There are no additional amino acid sources for earthworms but other soil animals and microorganisms. It is difficult to imagine that earthworms are carnivorous in temperate zone soils but with litter and soil they do consume microorganisms and small animals. Bacteria and protozoa, fungi and mesofauna dwell in other ecosystems than earthworms. Bacteria, Protozoa, Rotatoria, Tardigrada, and nematodes form ecosystems connected with water films in soil. Fungi, microarthropods and other small animals form ecosystems of soil and litter pores and gaps. Earthworms dwell in soil as a whole ecosystem. When they consume soil and litter they consume small ecosystems. Consumed bacterial populations also develop in their gut and are among the main sources of essential amino acids for earthworms. These bacteria form the gut ecosystem too. Hence earthworms are ecosystemivorous not saprovorous animals. (C) 1997 Elsevier Science Ltd.
