04411naa a2200157 a 450000100080000000500110000800800410001910000150006024500910007526000090016652037050017570000180388070000200389870000140391877303210393213150212008-10-03       2008    bl uuuu     u00u1 u    #d1 aRAMAJO, M.  aFeeding behaviour of Hormogaster elisae in three types of soil of laboratory cultures.  c2008  aDpto. Zoología y Antropología Física, Facultad de Biología, Universidad Complutense. 28040 Madrid (Spain) In a plot in El Molar (Madrid, Spain) three areas (A, B and C) with slightly different physicalchemical soil properties have been observed. Hernández et al. (2003) demonstrated that H. elisae is present mainly in zone A, whereas Ramajo (inedit) observed that the growth of this species in laboratory cultures is higher using zone C soil, reaching the highest growth using zone B soil. Ruiz et al. (2006) demonstrated that H. elisae in zone A seems to fragment the coarsest particles, becoming therefore a part of fine textural fractions, which are selected, on the other hand, by this species as these fractions are enriched with organic matter. The objective of the present study is to elucidate if the same feeding pattern is mantained in the three types of soil. Microcosms were prepared with each type of soil (A, B and C) sieved (4mm) and moistured reaching 20% humidity. One earthworm was introduced in each experimental microcosm, which was mantained during 7 days at 18ºC. Casts on the surface were separated daily and were frozen until their use. Physical-chemical fractionation of organic matter was studied with the obtained samples, being carbon separated and analysed in each of the fractions: free organic matter, free fulvics acids, humic acids, fulvic acids and humin. Mineral and organic fractions of the following particle sizes were separated: 2000 - 250 µm, 250 - 50 µm and 50 - 20 µm, and mineral-organic fraction 20 - 2 µm and &lt 2 µm, being carbon of the organic fraction analysed. The soil of zone A is poor in organic matter and presents a coarse texture, whereas B and C soils are comparatively richer in organic matter and their texture is finer. Chemical fractionation of organic matter shows that in B and C soils casts properties are significantly different from control soil in all the fractions. However, those differences were not observed in the soil of zone A. Casts of H. elisae are enriched in fulvic acids in soil of zones B and C; in zone B, more humificated fractions are less abundant in casts than in soil, obtaining oppossite results in zone C. The results of the physical fractionation of casts and soil in the three zones show that this species does not select the coarsest particles, but is capable of grinding some of them, or H. elisae is capable of breaking the aggregates, converting them, as a result, into the immediate lowersized fraction. This ability might be possible because of the existence of three gizzards in the digestive system of H. elisae. Contents in carbon and nitrogen of each of the fractions obtained in the physical fragmentation of casts is lower in zone A than in soil, while in the other two zones casts result enriched in carbon and nitrogen in fractions over 20 µm. With the obtained results, it can be concluded that in its own soil, H. elisae hardly modifyes the content in carbon and nitrogen in casts, but when this species is maintained in the other types of soil, besides increasing its weight, the content in organic matter of casts results different from the soil of the culture. In soil of zone B, casts present a higher content in carbon than soil in the least humificated fractions, whereas in soil C this increase occurs in all fractions. These results could point out that H. elisae when living in very poor soils, as it does in El Molar, takes advantage of all the available resources. Nevertheless, when it is mantained in richer soils in laboratory cultures, it ingests all the available food, but as this species does not manage to use it all, a part of it returns to the soil with casts.1 aJESÚS, J. B.1 aGUITIÉRREZ, M.1 aTRIGO, D.  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.