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al. 2005). In addition to mortality and reproduction, as typical high-level endpoints, con-
siderable attention has been focused on evaluating more sensitive physiological changes
induced by bioavailable toxic chemicals (Scott-Fordsmand and Weeks 2000). Lysosomal
membrane stability is one of the most commonly used biomarkers on earthworms. This
parameter has shown to be highly sensitive and able to detect the effects of minimal
amounts of toxic chemicals, in both laboratory and field conditions (Svendsen et al. 1996;
Weeks and Svendsen 1996; Rocco et al. 2011; Sforzini et al. 2011a). A reduction of lysosomal
membrane stability is often associated with an increase in the lysosome/cytoplasm vol-
ume ratio, a parameter indicating an unphysiological level of cell catabolism (Moore and
Viarengo 1987; Moore et al. 2008).
Recently, a battery of biomarkers suitable for proving pollutant-induced physiologi-
cal changes at different levels of functional complexity has been developed on
Eisenia
andrei
(Caselli et al. 2006; Gastaldi et al. 2007; Sforzini et al. 2011a, b), one of the most
commonly used earthworm species in ecotoxicology (OECD 1984, 2004; van Gestel et al.
1993; Saint-Denis et al. 1998; Robidoux et al. 2000). The set of physiological parameters
includes, among others, different lysosomal parameters at cellular level (i.e., lysosomal
membrane stability, lipofuscin, and neutral lipid lysosomal content) as well as tissue
damage (i.e., lysosome/cytoplasm volume ratio). Following an approach similar to that
used for the mussels (Dagnino et al. 2007), an expert system for biomarker data manage-
ment to evaluate the health status of the earthworms has been developed (Sforzini et al.
2011a). In the expert system procedures, lysosomal membrane stability and lysosome/
cytoplasm ratio are of particular relevance since they help to provide a reliable interpre-
tation of the physiological meaning in the changes observed in bell-shaped biomarkers
responses/reactions (such as enzymatic activities) that may give false negative results.
In particular, only when relevant alterations of both parameters are observed, does the
environmental expert system interpret the data of bell-shaped biomarkers as lying in
the decreasing part of the response curve. In these conditions, the results indicate an
augmented autophagic sequestration of cellular components, a process that may lead to
severe damage of cells and of tissue functions.
The successful transfer and application of lysosomal biomarker methodology to protis-
tans and earthworms underline the ubiquity of lysosomal responses and reactions to envi-
ronmental stressors. It further indicates that these biomarkers will probably have utility in
marine and estuarine protistans and annelids.
In the framework of OSPAR (2011), lysosomal stability has been proposed as a global
health status indicator in biomonitoring. This recommendation is based on the fact that
lysosomal membrane stability (LMS) appears to be largely independent of taxon, so “the
absolute values for measurement of lysosomal stability (NRR and cytochemical method)
are directly comparable. Furthermore, measurements of this biomarker in animals from
climatically and physically diverse terrestrial and aquatic ecosystems also indicate that it
is potentially a universal indicator of health status.”
5.6 Conclusions
There is overwhelming evidence that the lysosomal-autophagic system is ancient in evo-
lutionary terms and intimately tied in to the overall economy of eukaryotic cells. This sys-
tem can, therefore, be considered in a relatively generic manner across the phyletic range.
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