Growth of the Earthworm <i>Millsonia omodeoi</i> and Its Capacity to Accumulate Five Heavy Metals (HM) in Soils along a Toll Highway in Côte d’Ivoire

Abstract

The roads in correlation with the traffic linked to their existences are at the origin of the emission of numerous polluting substances likely to induce disturbances of the growth and the behavioral changes in the organisms living in their vicinities. The purpose of this study is to analyze the growth and capacity accumulation of a common earthworm species ( Millsonia omodeoi ) in Cu, Cr, Ni, Pb and Zn in soils along a main road called “Autoroute du Nord” in C ? te d’Ivoire. Thus, the earthworms were harvested in soils from a distance of 0 m (just after the sidewalk) to a distance of 200 m from the toll highway and in a control soil sampled in Lamto reserve (C ? te d’Ivoire). The study was carried out in the soil laboratory at the ecological station of Lamto reserve. The Ford-Walford technique was used to determine the model and parameters most appropriated for describing the growth of earthworms. A pairwise comparison of the growth parameters was carried out using the Kruskal-Wallis test with the STATISTICA 7.1 software. The heavy metals contained in the cultivated soils and earthworms were detected and quantified using a Scanning Electron Micro-scope (MEB FEG Supra 40 VP Zeiss) and an Atomic Absorption Spectrometer SPECTRA 110 (VARIAN). The capacity accumulation of heavy metals in earthworm was determined by the bioaccumulation factor (BAF) calculation. The results of this study showed that Gompertz is the most appropriated model to describe the growth of M. omodeoi . The life cycle of M. omodeoi shows that this earthworm adopts a K type demographic strategy. Cu is the most accumulated heavy metals in M. omodeoi , when Cr is the least accumulated. Concerning heavy metal content in the earthworms, it decreases while moving away from the pavement. These results highlight a possibility of choice of M. omodeoi as 1) indicators of heavy metals pollution and 2) target of biological organisms for environmental impact studies.