In feeding assays, there are several options when considering a food source. The
most common choice is to provide the Gammarids with conditioned organic material. Depending on the study, the adopted leaf species may be different. The most
commonly used leaves are alder (Alnus spp.), elm (Ulmus spp.), horse chestnut
(Aesculus spp.), maple (Acer spp.), poplar (Populus spp.) and oak (Quercus spp.)
(see Table 2). In some cases, the Gammarids’ diet is enriched with Tubifex worms
(Coulaud et al. 2011; Dedourge-Geffard et al. 2009; Geffard et al. 2010; Xuereb
et al. 2009). Occasionally, they are provided with other types of food, such as
alimentary chips (Novo Crabs®, JBL GmbH & Co., Germany) (Foucreau et al.
2014), Chironomidae (Gergs and Rothhaupt 2008), Artemia salina’s eggs
(Blockwell et al. 1998; Pascoe et al. 1995; Taylor et al. 1993), industrial shrimp
food (Henry et al. 2017), fish food (Semsar-kazerouni and Verberk 2018) or ground
and tropical fish food mix (Blockwell et al. 1996).
During the acclimation period, organisms are normally fed ad libitum with
pre-prepared conditioned leaves (Blarer and Burkhardt-Holm 2016; Blockwell
et al. 1998; Bloor 2010; Bundschuh et al. 2011b; Crane and Maltby 1991;
Dedourge-Geffard et al. 2009; Geffard et al. 2010; Naylor et al. 1989; Newton
et al. 2018; Xuereb et al. 2009; Zubrod et al. 2015). The conditioning process can
vary, and the differences between the techniques can be found in Table 2.
In behavioural studies, food is supplied to the organism during the testing regime
and is usually the same food type as provided during the acclimation period. The
type of food used in a study could influence the feeding activity, especially if the
organisms are fed on leaves that are not palatable or with leaves that have dissimilar
energy budgets (e.g. Agatz and Brown 2014).
Sometimes leaves are collected at the beginning or during fall, specifically
handpicked senescent Alnus glutinosa leaves that are not decomposed (Bundschuh
et al. 2009, 2017), whereas in other studies, the leaves are specifically collected after
they had abscised (Hargeby and Petersen 1988). After collection the leaves are either
used straight away or stored for later use (see Table 2). Storage methods vary
throughout the literature, for example, Bundschuh et al. (2009, 2011a, b, 2013,
2017) froze their leaves at À20
C, but this methodology ultimately alters the
structure of the leaves (Burke et al. 1976). More commonly, the leaves are dried at
room temperature and stored in the dark until needed (e.g. Naylor et al. 1989) (see
Table 2). However, Gessner et al. (1999) highlighted that drying leaves in an oven or
at room temperature ultimately ruins the leaf tissue. In the natural environment,
leaves usually reach water bodies soon after abscission (Fisher 1977). Consequently,
storing leaves for later use does not mimic the natural chain of events, and storing
will ultimately disrupt their structure. Gessner and Schwoerbel (1989) demonstrated
that freezing or drying leaves increases mass loss in the first few days when in water,
and this accelerates the conditioning process, which is usually statistically delayed in
fresh leaves (Bärlocher 1992).
The conditioning process involves soaking the leaves in water and mixing them
with an unknown fungi species (Nilsson 1974) or by inoculating the leaves with a
specific fungi species (Naylor et al. 1989). In the first instance, river water might be
used in the laboratory to condition the leaves, and it is usually inoculated with
12
G. Consolandi et al.
most common choice is to provide the Gammarids with conditioned organic material. Depending on the study, the adopted leaf species may be different. The most
commonly used leaves are alder (Alnus spp.), elm (Ulmus spp.), horse chestnut
(Aesculus spp.), maple (Acer spp.), poplar (Populus spp.) and oak (Quercus spp.)
(see Table 2). In some cases, the Gammarids’ diet is enriched with Tubifex worms
(Coulaud et al. 2011; Dedourge-Geffard et al. 2009; Geffard et al. 2010; Xuereb
et al. 2009). Occasionally, they are provided with other types of food, such as
alimentary chips (Novo Crabs®, JBL GmbH & Co., Germany) (Foucreau et al.
2014), Chironomidae (Gergs and Rothhaupt 2008), Artemia salina’s eggs
(Blockwell et al. 1998; Pascoe et al. 1995; Taylor et al. 1993), industrial shrimp
food (Henry et al. 2017), fish food (Semsar-kazerouni and Verberk 2018) or ground
and tropical fish food mix (Blockwell et al. 1996).
During the acclimation period, organisms are normally fed ad libitum with
pre-prepared conditioned leaves (Blarer and Burkhardt-Holm 2016; Blockwell
et al. 1998; Bloor 2010; Bundschuh et al. 2011b; Crane and Maltby 1991;
Dedourge-Geffard et al. 2009; Geffard et al. 2010; Naylor et al. 1989; Newton
et al. 2018; Xuereb et al. 2009; Zubrod et al. 2015). The conditioning process can
vary, and the differences between the techniques can be found in Table 2.
In behavioural studies, food is supplied to the organism during the testing regime
and is usually the same food type as provided during the acclimation period. The
type of food used in a study could influence the feeding activity, especially if the
organisms are fed on leaves that are not palatable or with leaves that have dissimilar
energy budgets (e.g. Agatz and Brown 2014).
Sometimes leaves are collected at the beginning or during fall, specifically
handpicked senescent Alnus glutinosa leaves that are not decomposed (Bundschuh
et al. 2009, 2017), whereas in other studies, the leaves are specifically collected after
they had abscised (Hargeby and Petersen 1988). After collection the leaves are either
used straight away or stored for later use (see Table 2). Storage methods vary
throughout the literature, for example, Bundschuh et al. (2009, 2011a, b, 2013,
2017) froze their leaves at À20
C, but this methodology ultimately alters the
structure of the leaves (Burke et al. 1976). More commonly, the leaves are dried at
room temperature and stored in the dark until needed (e.g. Naylor et al. 1989) (see
Table 2). However, Gessner et al. (1999) highlighted that drying leaves in an oven or
at room temperature ultimately ruins the leaf tissue. In the natural environment,
leaves usually reach water bodies soon after abscission (Fisher 1977). Consequently,
storing leaves for later use does not mimic the natural chain of events, and storing
will ultimately disrupt their structure. Gessner and Schwoerbel (1989) demonstrated
that freezing or drying leaves increases mass loss in the first few days when in water,
and this accelerates the conditioning process, which is usually statistically delayed in
fresh leaves (Bärlocher 1992).
The conditioning process involves soaking the leaves in water and mixing them
with an unknown fungi species (Nilsson 1974) or by inoculating the leaves with a
specific fungi species (Naylor et al. 1989). In the first instance, river water might be
used in the laboratory to condition the leaves, and it is usually inoculated with
12
G. Consolandi et al.