Original article Enhancement of growth and reproduction of the tropical earthworm Polypheretima elongata (Megascolecidae) by addition of Zea mays and Mucuna pruriens var. utilis litter to the soil E. Huerta a, *, C. Fragoso b , I. Barois b , P. Lavelle c a El Colegio de la Frontera Sur Unidad Villahermosa, Km 15.5 Carretera Villahermosa-Reforma, Ranchería Guineo 2a Sección, Villahermosa Tabasco, Mexico b Laboratoire d’Ecologie des Sols Tropicaux, Institut de Recherche pour le Développement (IRD), 32Av. Henri Varagnat, 93143 Bondy cedex, France c Departamento de Biología de Suelos, Instituto de Ecología A.C., A.P. 63 Xalapa, Ver. c.p. 91000, Mexico Received 10 January 2004; accepted 28 January 2005 Available online 08 June 2005 Abstract The effect of light fractions of organic matter of different origin, on the growth and reproduction of the mesohumic endogeic earthworm Polypheretima elongata, has been tested in laboratory cultures. Earthworms were fed with savannah soil from “La Mancha”Veracruz (Mexico), added with different amounts of fresh or composted Mucuna pruriens var. utilis (Leguminosae), or Zea mays (Graminaceae) leaf material. Earthworm cultures were performed under controlled conditions of temperature (27 °C) and humidity (33% on a dry weight basis) during 63 days for the growth study and 98 days for the reproduction study. The highest individual fresh weight (5.8 ± 0.7 g after 63 days) and the highest cocoon production (33 ± 8.4 cocoons ind -1 in 98 days) were obtained when litter of M. pruriens var. utilis was added to the soil. Mucuna leaf material was more efficient when fresh, whereas maize litter gave higher growth and fecundity rates when composted for 6 weeks. The addition of organic matter from the light fraction of the soil did not improve earthworm growth. © 2005 Elsevier SAS. All rights reserved. Keywords: Polypheretima elongata; Organic matter; Light fraction; Mucuna pruriens var. utilis; Zea mays 1. Introduction The tropical peregrine or cosmopolitan earthworm Polypheretima elongata (Perrier, 1872) [12–14] has been found widely distributed in Southeast Mexico [12]. It is an endogeic geophagous mesohumic species that can reach quite a large weight—up to 6 g fresh biomass after 100–120 days of growth—, and a high annual cocoon production of 40– 60 year –1 after 150 days [2]. According to the soil ecosystem engineer concept [17,20], this species influences the soil struc- ture [5–7], efficiently digests organic matter in mutualistic association with soil microflora [25], contributes to nutrient release [8], and provides favourable microenvironments for smaller decomposers [26]. Previous studies with Millsonia anomala and Pontoscolex corethrurus have shown that these beneficial effects may result in significant improvement of plant production when the average biomass of their popula- tions is greater than 30 g fresh weight per m 2 [9]. An addition of fresh or a bit decomposed leaf material can help increase earthworm biomass and growth in field conditions, as has been shown with M. anomala in African’s poor savannah soil [24]. In another study, Lavelle et al. [23] observed a two to three- fold increase in earthworm assimilation efficiency when fresh plant material, instead of humified, was added to the soil. The aim of this study was to identify ways to increase the * Corresponding author. E-mail address: ehuerta@vhs.ecosur.mx (E. Huerta). European Journal of Soil Biology 41 (2005) 45–53 www.elsevier.com/locate/ejsobi 1164-5563/$ - see front matter © 2005 Elsevier SAS. All rights reserved. doi:10.1016/j.ejsobi.2005.01.002