Résumé
Diplopods play a crucial role in litter decomposition via their transformation into fecal pellets, a process that contributes to the physical and chemical breakdown of organic matter. At the same time, different diplopod species may exhibit contrasting consumption strategies depending on the quality of the litter but also on the amount of soil ingested. Most of the experiments were conducted on a limited number of model species and without soil, which strongly limits our understanding of this process. Although geophagy is considered uncommon in diplopods, some studies show that diplopods can consume large amounts of soil. The objective of this study was to investigate the importance of geophagy in diplopods and its consequences on the feeding strategy of diplopods the main decomposer in the banana agroecosystems of Martinique. To this end, we conducted two different monospecific experiments in microcosm with 10 diplopod species from the island of Martinique, representing the three most common morphotypes (glomeroid, polydesmoid and juloid). In the first experiment, assimilation efficiency and specific litter consumption rate were measured in the absence of soil. In the second experiment, the proportion of soil in the diplopod diet (percentage of geophagy) and specific litter consumption in the presence of soil were measured. Our results showed a significant relationship between specific litter consumption and fresh biomass of diplopods in the absence of soil but no significant relationship in the presence of soil, showing the importance of considering soil in estimating litter consumption. We also found that decomposer macrofauna compensate for their consumption by having a higher specific litter consumption when soil is not available. This suggests an important nutritional role of soil in the diet of diplopods. In addition, we found that the proportion of soil in the diet ranged from 38% to 96% (66% on average for all species), higher rates than previously assumed. These results suggest that diplopods may have a generally important effect on soil processes such as soil structuring and bioturbation and that they are not only “litter transformer” but may also act as “soil engineers” to some extent