CHANGES IN RESPIRATION RATE AND SOME PHYSICOCHEMICAL PROPERTIES OF SOIL DURING GUT TRANSIT THROUGH ALLOLOBOPHORA-MOLLERI (LUMBRICIDAE, OLIGOCHAETA)

Some physicochemical and biological measurements were carried out on t he gut content and casts of Allolobophora molleri, an earthworm which lives in humid soils of Northern Spain. In the anterior part of the gu t, water (22% of moist weight of soil) and soluble organic matter (27. 4%) had been added to the ingested soil and pH had increased from 5.75 to 7.0. The amount of water-soluble compounds decreased sharply in th e middle and posterior parts of the gut and were hardly detectable in control soil or casts. The average O2 consumption, measured at 28-degr ees- and 21-degrees-C, indicated respectively 2.75- to 12-fold increas es in microbial respiration in the gut content compared to the non-ing ested soil. These results extend the hypothesis of a mutualistic diges tion in earthworms previously proposed for tropical endogeic species.