Effect of heavy metal exposure on blood haemoglobin concentration and methemoglobin percentage in Lumbricus terrestris

Abstract

The earthworm haemoglobin (Hb) is a large extracellular hemoprotein flowing in a closed circulatory system. In spite of the fundamental role of this respiratory pigment in earthworm physiology, little is known about its sensitivity to environmental pollutants. The aim of the present work was to investigate the possible effect of heavy metal (cadmium, copper, mercury) exposure on Hb concentration and oxidation state (methemoglobin formation) in the earthworm Lumbricus terrestris. In addition, the tissue concentration of metallothioneins, a well-known biomarker of heavy metal exposure, was determined as an indicator of metal uptake. The animals were exposed to increasing concentrations of Cd, Cu and Hg utilizing the standard acute toxicity test, "Filter paper test" for 48 h. Exposure to heavy metals (10(-5)-10(-3) M for Cd, 10(-4)-10(-3) M for Hg, and 10(-4)-10(-2) M for Cu) was found to increase haemoglobin concentration in L. terrestris, although the magnitude of such an increase was dependent on the metal. In addition, metal exposure led to the formation of methemoglobin. Compared to other known biological responses to heavy metals, such as metallothionein induction, methemoglobin increase showed a higher sensitivity and a higher percentage variation in exposed organisms, showing to be a possible suitable biomarker of exposure/effect to be included in a multi biomarker strategy in earthworm in soil monitoring assessment.

Metallothionein Induction in the Coelomic Fluid of the EarthwormLumbricus terrestrisfollowing Heavy Metal Exposure: A Short Report

“…They were divided into five subgroups: the first ( n = 30) was utilized as initial control (at time 0), the second ( n = 20) was exposed to copper sulphate, the third ( n = 20) was exposed to cadmium chloride, the fourth ( n = 20) was exposed to a mixture of the two metals, and the fifth was utilized as final control to be analyzed at the end of the exposure experiment. The exposure time was 72 h. As previously demonstrated [35], this time is sufficient to induce a significant response to heavy metal exposure in L. terrestris . The toxicant concentrations utilized were 45 mg/kg of soil for copper sulphate and 1 mg/kg of soil for cadmium chloride, respectively.…”

“…Previous studies demonstrated a significant induction of Mt proteins in different earthworm species such as Lumbricus rubellus , Eisenia fetida , and Eisenia andrei exposed to cadmium [31–33] or in Lumbricus mauritii exposed to Pb and Zn contaminated soil [27] and in Lumbricus terrestris exposed to cadmium, copper, and mercury [30, 34, 35]. Morgan et al [8] previously described the immunoperoxidase localization of Mt in the major organs and tissues of the earthworm Lumbricus rubellus sampled from a mine soil heavily polluted with Pb, Zn, and Cd.…”

Earthworm Biomarkers as Tools for Soil Pollution Assessment

“…Induction of MTs by metal exposure has been detected in a wide variety of organisms including earthworms (Stürzenbaum et al, 2001). For example a significant induction of MT proteins was observed in different earthworm species such as Lumbricus rubellus, Eisenia fetida, Eisenia andrei exposed to cadmium (Calisi et al, 2009;Demuynck et al, 2006;Ndayibagira et al, 2007;Brulle et al, 2007), or in Lumbricus mauritii exposed to Pb and Zn contaminated soil (Maity et al, 2011) and in Lumbriucus terrestris exposed to cadmium, copper and mercury (Calisi et al, 2011a). It is known that earthworms share a high tolerance to heavy metal exposure (Stürzenbaum et al, 1998) also thanks to the fundamental contribution of these metalbinding proteins.…”

“…In spite of the fundamental role of this respiratory pigment in earthworm physiology, little is known about its sensitivity to environmental pollutants. Recently Calisi et al (2011a) demonstrated heavy metal (cadmium, copper, mercury) exposure to significantly induce changes in either Hb concentration or its oxidation state in the earthworm Lumbricus terrestris. Exposure to heavy metals (10 -5 -10 -3 M for Cd, 10 -4 -10 -3 M for Hg, and 10 -4 -10 -2 M for Cu) was found to increase blood Hb concentration.…”

Effects of mercury on the life table demography of the rotifer Brachionus calyciflorus under different algal food (Scenedesmus obliquus) densities

“…Because of its environmental persistence and ability to be incorporated into food chains, the mercury accumulation in water might be magnified within ecosystems and be potentially hazard to invertebrates and fishes and ultimately jeopardize human health [9,10]. Therefore, knowledge of the toxicity of mercury to aquatic biota is of great importance.…”