03449naa a2200157 a 450000100080000000500110000800800410001910000180006024501380007826000090021652026970022570000150292270000150293770000180295277303210297013150222008-10-03       2008    bl uuuu     u00u1 u    #d1 aLÓPEZ, M. G.  aTHE EFFECT OF THE EARTHWORM Hormogaster elisae ON THE ABUNDANCE OF THE COLLEMBOLA Heteromurus nitidus IN SOIL FROM EL MOLAR (MADRID).  c2008  aSeveral authors (Maraun et al. 2001, 2003; Migge, 2001) have reported the negative influence of earthworms on the communities of microarthropods. The same trend has been reported for the endogeic Hormogaster elisae at El Molar (Madrid, Spain) by Gutiérrez et al., 2003. Other studies showed the favourable impact of earthworms on several arthropods species (Loranger et al 1998, Salmon and Ponge, 1999). The collembolan Heteromurus nitidus was reported to be more abundant in soils with the anecic earthworms Aporrectodea giardi and Lumbricus terrestris (Salmon and Ponge, 1999; Salmon, 2004; Salmon et al., 2005). The objective of the present study was to know if H. elisae (previously proved to negatively affect the microarthropod densities) produce attractive galleries for H. nitidus (usually attracted to earthworms galleries) or whether this collembolan species is also repelled by the soil disturbance generated by H. elisae. Six microcosms (plastic boxes of 18x12x6.5 cm) divided in two compartments with a 2mm pore-size mesh in the middle, were used. The mesh allowed H. nitidus to move around freely, from one compartment to another, but prevented the motion of earthworms. The microcosms were filled with soil from El Molar (Madrid) (400g in each compartment), and maintained at 15ºC and 20% humidity for 15 days. Two worms were placed in one of the compartments from each microcosm and 28 H. nitidus (14 in each compartment) were introduced in each microcosm. Another six control microcosms were set up with the same structure but without earthworms. After the 15 days had elapsed, the microcosms were disassembled and the Collembola occurring in the soil from the both compartments were extracted separately with the Berlese- Tulgren method. They were then counted under a stereomicroscope, distinguishing adult and juvenile individuals. A paired t-test was performed to compare the mean number of Collembola in each compartment. No significant differences were observed between the soil with or without earthworm, nor in adult H. nitidus, nor in juveniles. Two hypotheses may explain this result: (1) H. elisae has actually no influence on the behaviour and the survival of H. nitidus or (2) the positive effects would be counterbalanced by the negative ones, leading to the absence of visible effects of this earthworm specie on the collembolan H. nitidus. In fact, H. nitidus could have been attracted to the casts, mucus and urine from H. elisae, as it was to A. giardi excreta (Salmon and Ponge, 2001), and, in the same time, disturbed by the physical movement of the earthworm, or by a competition for food resources as it has been suggested in Gutiérrez et al. (2006).1 aSALMON, S.1 aAZA, D. T.1 aFERNANDEZ, R.  tIn: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.