1 Introduction
Freshwater Gammarids are common leaf-shredding detritivores, and they usually
feed on naturally conditioned organic material, in other words leaf litter that is
characterised by an increased palatability, due to the action and presence of microorganisms (Chaumot et al. 2015; Cummins 1974: Maltby et al. 2002). Gammarus
spp. are biologically omnivorous organisms, so they are involved in shredding leaf
litter and are also prone to cannibalism, predation behaviour (Kelly et al. 2002) and
coprophagy when juveniles (McCahon and Pascoe 1988). Gammarus spp. is a
keystone species (Woodward et al. 2008), and it plays an important role in the
decomposition of organic matter (Alonso et al. 2009; Bundschuh et al. 2013) and is
also a noteworthy prey for fish and birds (Andrén and Eriksson Wiklund 2013;
Blarer and Burkhardt-Holm 2016). Gammarids are considered to be fairly sensitive
to different contaminants (Ashauer et al. 2010; Bloor et al. 2005; Felten et al. 2008a;
Lahive et al. 2015; Kunz et al. 2010); in fact Amphipods have been reported to be
one of the most sensitive orders to metals and organic compounds (Wogram and
Liess 2001), which makes them representative test organisms for ecotoxicological
studies and valid sentinel species for assessing water quality status (Garcia-Galan
et al. 2017).
Since Gammarids play an important role in the breakdown of organic matter in
freshwater environments, it is understandable that their feeding behaviour is often
used as a sublethal endpoint, to investigate water quality status and the effects of
different contaminant types (Crane and Maltby 1991). Gammarid feeding activity
could be altered by the presence of contaminants in the water, which could potentially alter their food source, influence the organism’s biological function and cause
abnormal behavioural responses. These types of feeding investigation have been
carried out as in situ (i.e. directly in the environment) and ex situ (i.e. in the
laboratory) studies (Bundschuh et al. 2011b; Dedourge-Geffard et al. 2009; Maltby
et al. 2002; Zubrod et al. 2015). It has been demonstrated that feeding assays using
Gammarids are representative of natural leaf decomposition in the environment
(Maltby et al. 2002) and could be used to assess the effects of chemical contaminants
and also understand the consequences of new-generation contaminants, such as
plastic debris in freshwater environments (Blarer and Burkhardt-Holm 2016;
Weber et al. 2018). Even though feeding behaviour studies have been carried out
for almost half a century, there is a lack of standardisation for both ex situ and in situ
methods. Without standardisation, there is a risk that the effects of a test substance
could be under- or overestimated during in situ and ex situ approaches, which could
reduce their usefulness in environmental biomonitoring programs. This paper aims
to review the literature on feeding as an endpoint for amphipod ecotoxicology, by
highlighting disparities in the published methodologies, and to help develop
standardised protocols. Peer-reviewed literature was accessed through search
engines, databases and library archives. In general, most feeding studies have
reported four main stages: (1) acclimation period, (2) food preparation, (3) exposure
and (4) end of the experiment and feeding rate calculation. The aforementioned four
2
G. Consolandi et al.
Freshwater Gammarids are common leaf-shredding detritivores, and they usually
feed on naturally conditioned organic material, in other words leaf litter that is
characterised by an increased palatability, due to the action and presence of microorganisms (Chaumot et al. 2015; Cummins 1974: Maltby et al. 2002). Gammarus
spp. are biologically omnivorous organisms, so they are involved in shredding leaf
litter and are also prone to cannibalism, predation behaviour (Kelly et al. 2002) and
coprophagy when juveniles (McCahon and Pascoe 1988). Gammarus spp. is a
keystone species (Woodward et al. 2008), and it plays an important role in the
decomposition of organic matter (Alonso et al. 2009; Bundschuh et al. 2013) and is
also a noteworthy prey for fish and birds (Andrén and Eriksson Wiklund 2013;
Blarer and Burkhardt-Holm 2016). Gammarids are considered to be fairly sensitive
to different contaminants (Ashauer et al. 2010; Bloor et al. 2005; Felten et al. 2008a;
Lahive et al. 2015; Kunz et al. 2010); in fact Amphipods have been reported to be
one of the most sensitive orders to metals and organic compounds (Wogram and
Liess 2001), which makes them representative test organisms for ecotoxicological
studies and valid sentinel species for assessing water quality status (Garcia-Galan
et al. 2017).
Since Gammarids play an important role in the breakdown of organic matter in
freshwater environments, it is understandable that their feeding behaviour is often
used as a sublethal endpoint, to investigate water quality status and the effects of
different contaminant types (Crane and Maltby 1991). Gammarid feeding activity
could be altered by the presence of contaminants in the water, which could potentially alter their food source, influence the organism’s biological function and cause
abnormal behavioural responses. These types of feeding investigation have been
carried out as in situ (i.e. directly in the environment) and ex situ (i.e. in the
laboratory) studies (Bundschuh et al. 2011b; Dedourge-Geffard et al. 2009; Maltby
et al. 2002; Zubrod et al. 2015). It has been demonstrated that feeding assays using
Gammarids are representative of natural leaf decomposition in the environment
(Maltby et al. 2002) and could be used to assess the effects of chemical contaminants
and also understand the consequences of new-generation contaminants, such as
plastic debris in freshwater environments (Blarer and Burkhardt-Holm 2016;
Weber et al. 2018). Even though feeding behaviour studies have been carried out
for almost half a century, there is a lack of standardisation for both ex situ and in situ
methods. Without standardisation, there is a risk that the effects of a test substance
could be under- or overestimated during in situ and ex situ approaches, which could
reduce their usefulness in environmental biomonitoring programs. This paper aims
to review the literature on feeding as an endpoint for amphipod ecotoxicology, by
highlighting disparities in the published methodologies, and to help develop
standardised protocols. Peer-reviewed literature was accessed through search
engines, databases and library archives. In general, most feeding studies have
reported four main stages: (1) acclimation period, (2) food preparation, (3) exposure
and (4) end of the experiment and feeding rate calculation. The aforementioned four
2
G. Consolandi et al.