Biomarkers In Earthworms Research Articles

A review of lysosomal membrane stability measured by neutral red retention: is it a workable earthworm biomarker?

The ability of biomarkers to integrate effects of chemicals on biota has lead to increased calls for their application in assessing the status of polluted ecosystems. In tandem there has been an increase in our knowledge of the ecophysiological responses of keystone species to pollutants, which has allowed the development of a number of promising methods. In contrast to the number of biomarker development studies, the number of biomarker validation studies has remained limited. This paper redresses this imbalance by drawing together data from studies that have used the earthworm lysosomal membrane stability response (measured using the neutral red retention assay). This review first gives a short history of the biomarker's development. Second, it sets published applications of the technique against established criteria for a “good” biomarker (i.e., dose–response relationship, sensitivity, ecological relevance, confounding factors, chemical specificity, species differences, time–response relationship, methodological concerns, and overall public/regulator confidence, and acceptance). Discussion of the biomarker's suitability to each criterion is followed by an overall evaluation of its workability for routine soil quality assessment and caveats for its use.

Use of biomarkers in earthworms to detect use and abuse of field applications of a model organophosphate pesticide.

Use of biomarkers in earthworms to detect use and abuse of field applications of a model organophosphate pesticide.

Use of Biomarkers in Earthworms to Detect Use and Abuse of Field Applications of a Model Organophosphate Pesticide

Use of Biomarkers in Earthworms to Detect Use and Abuse of Field Applications of a Model Organophosphate Pesticide

Biomarkers in earthworms.

Earthworms are believed to be so-called key species within ecosystems and are often exposed to a wide range of anthropogenic compounds released to the terrestrial environment. As a consequence, they may suffer from the toxicity of these compounds. For these and other reasons, earthworms have been used extensively in ecotoxicological studies. In recent years the use of other biological responses (biomarkers) to estimate either exposure or resultant effects of chemicals has received increased attention. Biomarkers address the question of bioavailability by only responding to the bioactive fraction. They may incorporate effects following exposure to a mixture of chemicals. Biomarkers may also reduce extrapolation of results from the laboratory to the field, as they may be applicable under both conditions. The present review has drawn together current knowledge on potential biomarkers in earthworms and appraised them in relation to basic requirements needed for supplying information relevant to devising satisfactory risk assessment. A wide range of potential biomarkers have been measured in earthworms, including DNA alteration, induction of metal-binding proteins (MTs and MBP), depression of ChE activity and other enzymatic responses, energy reserve responses, responses in neural impulse conductivity, lysosomal membrane stability, immunological responses, changes in sperm numbers, histopathological changes, and behavioral changes. Both organic and inorganic compounds have been included; however, for each biomarker the main emphasis historically has been placed on only a few chemicals. Dose-response relationships were in some cases observed. Little information is available on the linkage of the biomarker response to effects at population or community levels. The influence of other factors, biotic and abiotic, on the biomarker responses and their temporal duration have been only sporadically reported.

Toxicity of nickel to the earthworm and the applicability of the neutral red retention assay

The toxic effects of nickel on survival, growth, and reproduction of Eisenia veneta were investigated following 4 weeks of exposure to a nickel-chloride spiked loamy sand soil. The ability of a simple earthworm biomarker, the lysosomal membrane stability of coelomocytes, to reflect nickel exposure was also studied. Nickel caused a significant toxic effect on E.veneta at soil concentrations above 85 mg Ni/kg. Reproduction (cocoon production) was the most sensitive parameter being reduced at soil concentrations above 85 mg Ni/kg (EC10 = 85 mg Ni/kg). Survival of adults was only reduced at concentrations above 245 mg Ni/kg, while adult and cocoon wet weight were not affected by soil nickel concentrations up to 700 mg Ni/kg. The lysosomal membrane stability, measured as neutral-red retention time, was reduced at soil nickel concentrations similar to those that reduced reproduction, and demonstrated a dose-response relationship. The neutral-red retention time showed large individual variation for the earthworms within each exposure concentration. It was concluded that the lysosomal membrane stability, measured as neutral red retention time, has a potential role in risk assessment, but care should be taken conducting this test.

Relevance and Applicability of a Simple Earthworm Biomarker of Copper Exposure. II. Validation and Applicability under Field Conditions in a Mesocosm Experiment withLumbricus rubellus

EarthwormsLumbricus rubelluswere exposed to a range of increasing soil copper concentrations in a mesocosm experiment for 17, 40, 70, and 110 days, respectively. Neutral-red retention times were measured along with earthworm tissue copper residues and earthworm growth and survival. The neutral-red retention assay demonstrated a clear dose–response threshold preceding a copper exposure value where increased regulatory activity had resulted in the copper bioconcentration factor (BCF) decreasing from 1 to 0.5. Effects on earthworm growth and survival occurred only at soil copper concentrations where the earthworm BCFs were lowered to ca. 0.5. Thus, the position of the neutral-red threshold could potentially make it possible to differentiate between copper exposure and actual toxicity. In terms of field applicability it was demonstrated that natural and seasonal variations in climatic parameters had little or no effect on the neutral-red response. Neutral-red retention assay has a potential role in environmental risk assessment and routine monitoring, as it is likely to provide a sufficiently accurate warning of impending ecological damage at a level below that found to cause actual physiological damage to the earthworms.

Relevance and Applicability of a Simple Earthworm Biomarker of Copper Exposure. I. Links to Ecological Effects in a Laboratory Study withEisenia andrei

A simple earthworm biomarker, neutral-red retention by coelomocyte lysosomes, was measured concurrently with ecological parameters in order to link effects at different levels of biological organization in a laboratory study. Exposure of the earthwormEisenia andreito an increasing range of soil copper concentrations in the laboratory indicated a threshold range for the neutral-red assay at soil copper concentrations between 40 and 80 mg Cu kg−1. This threshold coincided with the soil to worm copper bioconcentration factor decreasing from 1 to 0.3 and thus an apparent onset of a copper regulatory mechanism. Effects at the individual and population levels only occurred at soil copper concentrations beyond that of the biomarker threshold. Thus, it was possible to differentiate between exposure and toxicity. It was therefore possible to conclude that the neutral-red assay has great potential and relevance in earthworm ecotoxicity studies. The assay provides an early warning that can be linked directly to important physiological changes that were observed to precede adverse effects on individuals or populations in this laboratory study.