as implementing equally informative conservative techniques that do not require
sacrifice or preliminary screening in vitro tools are encouraged. A detailed description on the most commonly used biomarkers in earthworm studies addressing soil
pollution monitoring is given in a former and fairly recent book chapter [12]. However, in this issue, the most recent genomic and metabolomics applications in
earthworm studies as promising biomarker molecular tools will be included.
The biomarkers considered here will refer mostly to sub-individual responses
adopted in earthworm studies for the last 5 years on chemical toxicity assessment in
laboratory exposures either using the filter paper contact tests or using spiked
artificial or natural soils or even those conducted under realistic field conditions
(mostly at a mesoscale). These studies embrace biomarkers informing on changes on
enzyme activities and/or gene expression and endogenous metabolite composition,
but also on the occurrence of damage to biomolecules such as DNA, proteins and
lipids and alterations in lysosomal membrane stability, in immunology defences and
in histological features caused by a range of anthropogenic chemicals acting either
alone or in combination. A comprehensive table gathering many of these studies was
already presented in the Pelosi et al. [4] review mostly in relation to pesticide
exposures. Here a selection of more recent work (>2014) using earthworm biomarkers in relation to metal and pesticide exposures in agricultural soil relevant
species will be considered, and emphasis will be placed on the toxicity studies
addressing chemicals of more recent environmental concern known as emerging
contaminants. As anticipated, studies screening for the toxicity associated with novel
contaminants have mostly been based on the model earthworms (Eisenia spp.)
adopted in soil ecotoxicology testing. Even though a larger body of literature
correspond to this group, it is important to highlight the fact that a few research
studies include more ecologically relevant species such as L. terrestris.
2 Ecotoxicological Biomarkers: An Overview
The biomarkers most frequently applied in earthworm studies are either those
responsive to a particular type of chemical or those informative of a general stress
status. For instance, metallothionein content specifically responds to metal exposures, but it has also been seen to be affected by other chemical stressors and given a
protection role in invertebrates. Cholinesterases and in particular acetylcholinesterase (AChE) and carboxylesterase (CE) activities specifically respond to pesticides.
While inhibition of AChE activity is considered a sign of neurotoxicity, the inhibition of CEs by pesticides (through stoichiometric binding) is considered a protective
mechanism towards preventing neurotoxicity (AChE inhibition) under pesticide
exposures. However, CEs also play a key role in endogenous as well as xenobiotic
metabolism (phase I hydrolysis); thus, their modulation could compromise physiological and detoxication processes [13]. Other phase I oxidoreduction reactions such
as those involving cytochrome P450 and its associated enzymatic activities
(e.g. ethoxyresorufin-O-deethylase (EROD)) are present but less represented and
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M. Solé
sacrifice or preliminary screening in vitro tools are encouraged. A detailed description on the most commonly used biomarkers in earthworm studies addressing soil
pollution monitoring is given in a former and fairly recent book chapter [12]. However, in this issue, the most recent genomic and metabolomics applications in
earthworm studies as promising biomarker molecular tools will be included.
The biomarkers considered here will refer mostly to sub-individual responses
adopted in earthworm studies for the last 5 years on chemical toxicity assessment in
laboratory exposures either using the filter paper contact tests or using spiked
artificial or natural soils or even those conducted under realistic field conditions
(mostly at a mesoscale). These studies embrace biomarkers informing on changes on
enzyme activities and/or gene expression and endogenous metabolite composition,
but also on the occurrence of damage to biomolecules such as DNA, proteins and
lipids and alterations in lysosomal membrane stability, in immunology defences and
in histological features caused by a range of anthropogenic chemicals acting either
alone or in combination. A comprehensive table gathering many of these studies was
already presented in the Pelosi et al. [4] review mostly in relation to pesticide
exposures. Here a selection of more recent work (>2014) using earthworm biomarkers in relation to metal and pesticide exposures in agricultural soil relevant
species will be considered, and emphasis will be placed on the toxicity studies
addressing chemicals of more recent environmental concern known as emerging
contaminants. As anticipated, studies screening for the toxicity associated with novel
contaminants have mostly been based on the model earthworms (Eisenia spp.)
adopted in soil ecotoxicology testing. Even though a larger body of literature
correspond to this group, it is important to highlight the fact that a few research
studies include more ecologically relevant species such as L. terrestris.
2 Ecotoxicological Biomarkers: An Overview
The biomarkers most frequently applied in earthworm studies are either those
responsive to a particular type of chemical or those informative of a general stress
status. For instance, metallothionein content specifically responds to metal exposures, but it has also been seen to be affected by other chemical stressors and given a
protection role in invertebrates. Cholinesterases and in particular acetylcholinesterase (AChE) and carboxylesterase (CE) activities specifically respond to pesticides.
While inhibition of AChE activity is considered a sign of neurotoxicity, the inhibition of CEs by pesticides (through stoichiometric binding) is considered a protective
mechanism towards preventing neurotoxicity (AChE inhibition) under pesticide
exposures. However, CEs also play a key role in endogenous as well as xenobiotic
metabolism (phase I hydrolysis); thus, their modulation could compromise physiological and detoxication processes [13]. Other phase I oxidoreduction reactions such
as those involving cytochrome P450 and its associated enzymatic activities
(e.g. ethoxyresorufin-O-deethylase (EROD)) are present but less represented and
314
M. Solé