RESEARCH ON THE ECOLOGY OF ASTACOPSIDRILUS-NACERI GIANI AND MARTIN, 1995 (PHREODRILIDAE, OLIGOCHAETA) FROM THE GROUNDWATERS OF MOROCCO

An ecological approach to the distribution of Astacopsidrilus naceri i n wells and hyporheic zone of rivers in the western High Atlas (Morocc o) has enabled us to categorise this n. species as a member of stygofa una and demonstrate its preference for hyporheic biotopes and sandy se diments, as well as the preponderant role of granulometric factors in its distribution. The gut content of two taxa, Astacopsidrilus and Tri chodrilus, cohabiting and predominating the oligochaete fauna in the u nderflow of Oued Makhfaman, a tributary of Oued N'Fis (High Atlas, nea r Marrakech), could be characterized by the amount and size of the ing ested sandy particles. This analysis showed a greater absorbency of th e digestive system of Astacopsidrilus naceri, in comparison with to th e genus Trichodrilus which is strictly limivorous. This suggests a com petitiveness between these two taxa.