However, not affect E. fetida as they affect

However, in the present study, new analyses with FTIR-ATR and
NMR also were carried out to verify these same molecular changes in the exposed
individuals of E. fetida. Unlike with
E. andrei, it was not possible to
identify the same underlying molecular responses to exposure to the same
concentrations of MPs. As indicated in Table 2 and Figure 3, no apparent differences between treatments were detected with FTIR-ATR analyses. Regarding
NMR analyses, a clear difference for 62.5 mg kg-1 was detected (Table 3).An
explanation to these results could be that
microplastics do not affect E. fetida
as they affect E. andrei. Biochemical
differences may be evaluated through
stress biomarkers (Figure 1 and 2), but these differences were not
“quantifiable” when resorting to FTIR-ATR analyses (Tables 2 and 3, Figure 3). As
indicated by Dominguez and Edwards (2001), both
species have similar ecological and physiological characteristics, although can
also exhibit several differences, such as growth rates and cocoon production,
which are slightly higher in E. andrei.
Additionally, it has been demonstrated that it is not always possible to assume
an equal response to the same contaminant (Reinecke and Viljoen, 1991; Albani
et al., 2003; Domínguez et al., 2005; Pelosi et al., 2013) and, therefore, their
response to stress factors may be different (Domínguez et al., 2005).In this sense, Bundy et al.
(2002) showed that Eisenia species
differ markedly in their biochemical profiles through NMR analyses. Also,
Albani et al. (2003) showed, by a fluorescent
fingerprinting technique, that E.
andrei and E. fetida do not metabolise the same type of molecules and for
these reasons, can be differentiated at
the molecular level. These authors explained that “both species have a
different molecular composition in their coelomic fluid and thus have different
metabolisms”. As a result, these authors also indicated, “interpretations of
immunological studies obtained on earthworms could be significantly different
depending upon the differences in species”. In
addition, a later review of Pelosi et al. (2013) showed that E. fetida is less sensitive to
pesticides than species found in cultivated fields (e.g. E. andrei). Thus
such differences in sensitivity could be extended to many other contaminants.Finally, a cluster analysis
was performed to integrate all biomarkers data, FTIR-ATR areas for each wavenumber
interval (cm-1) and NMR analyses, allow identifying two groups differentiated
by the concentrations of MPs above 250 mg kg-1 (Figure 4). In a previous paper, histopathological changes were recorded for concentrations above 125 mg
kg-1 that reinforce our idea over a lower sensitivity of E. fetida than E. andrei to the same
pollutant. Nevertheless, Further studies should be
carried out to confirm this hypothesis.