phosphate (TPhP) toxicity was addressed under acute filter paper contact test and
chronic soil exposures in the epigeic earthworm P. excavatus using a metabolomics
and metabolite identification approach [70]. About ten endogenous metabolites and
seven phospholipids were modified as seen by GC-MS and LC-QTOF methodologies due to TPhP.
Ionic liquids (ILs) are chemicals largely used in electric battery applications due
to their chemical and thermodynamic stability and have been proposed as “green
alternatives” to traditional solvents. However, their increasing use in technological,
industrial and more recently scientific and medical applications could constitute a
threat to biota present in soils contaminated with e-waste residues [71]. So far, all the
studies conducted on assessing their toxicity have been based on E. fetida as the
model. The potential toxicity of the imidazole-based IL, 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim]BF4), was evaluated in earthworms
inhabiting artificial and natural contaminated soils in experiments for up to 28 days
with greater toxicity observed in the earthworms from fluvo-aquic natural soils
[72]. Another similar study but with the imidazole-based IL, 1-octyl-3methylimidazolium hexafluorophosphate ([omim]PF6), was conducted in the same
species under laboratory soil conditions for the same time period and with coincident
endpoints [73]. Maximal ROS production and LPO occurrence were observed at
concentrations of 40 mg kg
À1 after 28 days. Likewise, DNA damage (using comet
assay) was revealed as the most sensitive endpoint which increased over time and
dose. The toxicity associated with two ILs, [Omim]BF4 and [Omim]Br, was
contrasted under similar soil conditions, and the targeted endpoints revealed a
negative impact time- and dose-dependent on DNA damage (measured as olive
tail moment) even though antioxidant defences were also enhanced [74]. The influence of the length chain of the IL, 1-alkyl-3-methyl imidazole bromide ionic
[C n mim]Br, from n ¼ 2, 4, 6, 10 and 12 was also tested in a sub chronic toxicity
text in E. fetida in the conditions described above, but in this case the endpoints were
measured only after 14- and 28-day soil exposures [75]. Their conclusions revealed
that toxicity increased with length chain but decreased after C 10 . The same experimental design and endpoints were applied to a chloride-derived IL, 1-octyl-3methylimidazolium chloride ([C8mim]Cl), in E. fetida [76]. In this case, biochemical modifications of antioxidant defences did not prevent occurrence of damage
(increased LPO and DNA levels) in a dose- and time-dependent fashion.
9 Earthworm Metabolism and Metabolite Identification
Metabolism may play a significant role in toxicity by two mechanisms: (1) it affects
the bioaccumulation of chemicals and (2) it can originate metabolites with enhanced
toxicity in respect to the parent compound. A comprehensive review on the earthworm’s metabolism was published in 2015 by Katagi and Ose [77], but it was
centred mostly on pesticide exposures. Depending on the chemical’s nature, metabolism can lead to the formation of more reactive metabolites such is the case of OP
Biomarkers in Earthworms
331
chronic soil exposures in the epigeic earthworm P. excavatus using a metabolomics
and metabolite identification approach [70]. About ten endogenous metabolites and
seven phospholipids were modified as seen by GC-MS and LC-QTOF methodologies due to TPhP.
Ionic liquids (ILs) are chemicals largely used in electric battery applications due
to their chemical and thermodynamic stability and have been proposed as “green
alternatives” to traditional solvents. However, their increasing use in technological,
industrial and more recently scientific and medical applications could constitute a
threat to biota present in soils contaminated with e-waste residues [71]. So far, all the
studies conducted on assessing their toxicity have been based on E. fetida as the
model. The potential toxicity of the imidazole-based IL, 1-butyl-3methylimidazolium tetrafluoroborate ([Bmim]BF4), was evaluated in earthworms
inhabiting artificial and natural contaminated soils in experiments for up to 28 days
with greater toxicity observed in the earthworms from fluvo-aquic natural soils
[72]. Another similar study but with the imidazole-based IL, 1-octyl-3methylimidazolium hexafluorophosphate ([omim]PF6), was conducted in the same
species under laboratory soil conditions for the same time period and with coincident
endpoints [73]. Maximal ROS production and LPO occurrence were observed at
concentrations of 40 mg kg
À1 after 28 days. Likewise, DNA damage (using comet
assay) was revealed as the most sensitive endpoint which increased over time and
dose. The toxicity associated with two ILs, [Omim]BF4 and [Omim]Br, was
contrasted under similar soil conditions, and the targeted endpoints revealed a
negative impact time- and dose-dependent on DNA damage (measured as olive
tail moment) even though antioxidant defences were also enhanced [74]. The influence of the length chain of the IL, 1-alkyl-3-methyl imidazole bromide ionic
[C n mim]Br, from n ¼ 2, 4, 6, 10 and 12 was also tested in a sub chronic toxicity
text in E. fetida in the conditions described above, but in this case the endpoints were
measured only after 14- and 28-day soil exposures [75]. Their conclusions revealed
that toxicity increased with length chain but decreased after C 10 . The same experimental design and endpoints were applied to a chloride-derived IL, 1-octyl-3methylimidazolium chloride ([C8mim]Cl), in E. fetida [76]. In this case, biochemical modifications of antioxidant defences did not prevent occurrence of damage
(increased LPO and DNA levels) in a dose- and time-dependent fashion.
9 Earthworm Metabolism and Metabolite Identification
Metabolism may play a significant role in toxicity by two mechanisms: (1) it affects
the bioaccumulation of chemicals and (2) it can originate metabolites with enhanced
toxicity in respect to the parent compound. A comprehensive review on the earthworm’s metabolism was published in 2015 by Katagi and Ose [77], but it was
centred mostly on pesticide exposures. Depending on the chemical’s nature, metabolism can lead to the formation of more reactive metabolites such is the case of OP
Biomarkers in Earthworms
331