Influence of different food substrates on growth and reproduction of two tropical earthworm species ( Pontoscolex corethrurus and Amynthas corticis) : The 7th international symposium on earthworm ecology · Cardiff · Wales · 2002

Abstract

In order to evaluate the effect of different plant residues on growth and reproduction of two ecologically different tropical earthworms, cultures of the endogeic Pontoscolex corethrurus and the epigeic Amynthas corticis were maintained in microcosm laboratory experiments. Fresh leaves of mucuna (Mucuna pruriens) and cacahuatillo (Araquis pintoi), litter of macadamia (Macadamia tetraphyla) and sawdust (Pinus patula), considered respectively as high, medium and low quality residues were tested in six different mixtures that included mineral soil as the main substrate. For each earthworm species one individual per pot (three replicates) was inoculated (in a completely randomized experimental design) in the following treatments: soil-mucuna (28:1), soil-sawdust-mucuna (21:7:1), soil-macadamia (28:1), soil-sawdust-macadamia (21:7:1), soil-cacahuatillo (28:1) and soil-sawdust-cacahuatillo (21:7:1). Weight and cocoon production were recorded each 12 days. Maximal weight for the endogeic P. corethrurus was observed in soil-mucuna-sawdust whereas minimal weights were obtained in all cacahuatillo treatments. Growth rates varied from 13.6 mg day−1 (soil-sawdust-mucuna) to –1.2 mg day−1 (soil-cacahuatillo). P. corethrurus reproduced in all treatments except those in which cacahuatillo was included. Lower and higher fecundity rates were observed in, respectively, soil-sawdust-mucuna (average 23.9 cocoons year−1) and soil-sawdust-macadamia (average 56.5 cocoons year−1). Biomass of the epigeic A. corticis was higher in soil-sawdust-mucuna and lower in soil-cacahuatillo treatments. Growth rates varied from 7.4 mg day−1 (soil- sawdust-macadamia) to 0.33 mg day−1 (soil-cacahuatillo). A. corticis reproduced mainly in treatments that included sawdust. Highest fecundity rates were found in soil-sawdust-mucuna (233.6 cocoons year−1) and lower in soil-mucuna treatments (31.1 cocoons year−1). We conclude that in order to maintain successful field populations of endogeic and epiendogeic species, it is necessary to add mixtures of high and low quality organic residues.