Diet of an anecic earthworms from the Colombian savannas: a question about ecological categories

An ecological classification based on a set of morphological characters may be used to describe earthworm functions in soil. However these relationships have been seldom verified. Gizzards of the earthworm Martiodrilus carimaguensis (Glossoscolecidae) were studied to find out if its anecic morphology was in agreement with its diet (shallow litter remains and deep organo-mineral material). By direct observation of 13 adults` gizzard. contents with a dissecting and a phase contrast microscope, the volumetric percentage of plant fragments, roots, amorphous organic matter, and mineral particles reached, respectively, 5.5%, 6.3%, 5%, and 35% V/V. Eighty percent of plant fragments were microscopic, and mostly incorporated into the organo-mineral earthworm casts well preserved in the gizzard. Coprophagy and necro-rhizophagy were the dominant feature of M. carimaguensis diet. Yet, the casts produced revealed a high variability in its diet, what could be related to transitional adoption of a typical anecic diet during some periods.