Biometric relationships in earthworms (Oligochaeta)

Digging and hand-sorting of soil blocks is a very widespread method in the study of earthworm communities. One disadvantage of this method is that it is very time consuming and often many earthworms are incomplete because the y were cut by the digging tools. When authors report earthworm biomass, no mention is made of the assessment of any relationship between the mass of t hose cut earthworms and their overall weight. In such cases, biomass is gen erally underestimated. In this paper, our objective was to propose a new me thod to estimate the weight of incomplete earthworms on the basis of precli tellar diameter and its usefulness for studying the dynamics of earthworm p opulations. Complete earthworms were collected from samplings performed in native savannahs and man made pastures of the eastern plains of Colombia an d from a poplar grove (Populus sp.) in Central Spain. A strong correlation between the preserved fresh weight and the maximum preclitellar diameter wa s found for all the species studied. Three types of models have provided a convenient method to estimate earthworm biomass: (i) linear for almost all the species; (ii) exponential for a large Neotropical anecic species, Marti odrilus carimaguensis (Glossoscolecidae); and (iii) second degree polynomic equation. (C) 2000 Editions scientifiques et medicales Elsevier SAS.