Agriculture Reference
In-Depth Information
3.1 Terrestrial invertebrates
Terrestrial arthropods of the saprophagous fauna such as, Isopoda, Collembola and
Diplopoda are among the most appropriate organisms to evaluate the effects of the
accumulation of toxic substances present in the soil, due to their direct contact with
contaminants present in it (Gräff et al., 1997; Hopkin et al., 1989). Annelids, in special the
Oligochaeta, are also frequently used in toxicity tests. These invertebrates get in contact with
a great variety of pollutants present in this compartment by their movement and ingestion
of contaminated soil or leaf litter (Spadotto et al.
2004).
Oligochaeta are considered one of most important representatives of the edaphic macro-
fauna (Kale, 1988). Several factors make earthworms excellent bioindicators of the toxicity of
chemical substances in the soil, such as the knowledge already accumulated on their
habitats and important trophic position of these invertebrates, which are situated in the
lowest levels of the terrestrial food webs, serving as food for several animals and route of
transference and biomagnification of contaminants along these webs (Andréa, 2010).
Due to their great importance in the soil, their wide distribution and all the reasons
previously cited, earthworms, mainly the species
Eisenia fetida
(figure 1) and
E. andrei
were
chosen for several toxicity tests for registration of agrochemicals in the regulatory agencies
of several countries, including Brazil (Andréa, 2010). Other species such as
Lumbricus
terrestris
and
L. rubellus
have been widely used in studies of bioaccumulation of metals
(Amaral & Rodrigues, 2005; Veltman et al., 2007).
Fig. 1. Earthworm
Eisenia fetida.
(Photo: Raphael Bastão de Souza and Larissa Rosa Nogarol)
Collembola are among the most important members of the soil meso-fauna involved in the
decomposition process and are vulnerable to the effects of its contamination (Bengtsson &
Rundgren, 1984). Greensdale (2007) lists some favourable points in choosing Collembola as
bioindicators, such as presence in all ecosystems, abundance and ease of collection in
sufficient number to allow statistical analyses. Moreover, they have short life cycle, making
that they respond quickly to environmental changes and, as they are in direct contact with
the soil, they are more sensitive to some type of stress applied in the ecosystem.
Several studies point out this organism as bioindicator, applying different methodologies
and evaluation parameter. Tests of reproduction associated to survival rates (Pedersen et al.,
2009; Sverdrup et al., 2010;) and evaluation of abundance and/or diversity of species in
areas that suffer some type of degradation (Sousa et al., 2004) are the most used
methodologies.
Another taxonomic group used in toxicological analyses is Isopoda, one of the largest orders
of crustaceans with approximately 10,000 thousand described species, mostly marine
