with a light/dark cycle of 16:8 h (Weber et al. 2018) or autumn with a cycle of
10:14 h (Garcia-Galan et al. 2017) (see Table 1). Adopting different light/dark cycles
could make the comparison between studies challenging, since light could influence
the organisms’ physiological processes and behaviour (Perrot-Minnot et al. 2013).
2.4 Media Selection
The type of media selected for an experiment is another factor that could have an
impact on the outcome of a study. Some researchers prefer to use an artificial
medium (see Table 1) that guarantees standardisation (Agatz et al. 2014; Maltby
et al. 2002), and in other studies, river water is sometimes used as a medium.
However, river water might be contaminated, and this could therefore interfere
with the organisms’ cleansing process during their acclimation period, which
makes it a peculiar choice of test media. Numerous studies have also used river
water or a mixture (Alonso et al. 2009; Blarer and Burkhardt-Holm 2016;
Bundschuh et al. 2009, 2017; De Castro-Català et al. 2017; Dedourge-Geffard
et al. 2009; Gergs and Rothhaupt 2008; Iltis et al. 2017; Maul et al. 2006; Zubrod
et al. 2015) (see Table 1). For example, Bundschuh et al. (2017) combined river
water with tap water, which also has limitations as the tap water could be contaminated (Magi et al. 2018). Potentially, any type of water could be contaminated,
which is why the authors recommend that researchers should report the chemical
breakdown (i.e. presence of contaminants) of their chosen water media along with
their study findings so that any contamination is transparent.
Gammarus pulex allocates up to 11% of its energy supply to osmotic regulation
(Sutcliffe 1984), and Gammarids have been proven to be acid-sensitive (Gammarus
fossarum; Felten and Guerold 2001; Gammarus pulex, Sutcliffe and Carrick 1973).
In fact, acidic conditions induce a range of physiological and behavioural alterations,
such as a reduction in the ventilation activity of Gammarus pulex (Felten et al.
2008b). These findings highlight the importance of measuring pH, as a shift in pH
might influence the outcome of an experiment and prevent comparisons between
studies. pH is rarely reported and presumably not measured in the environment
during the collection process, the acclimation period or the experiment. Along with
the chemical parameters of the acclimation media, the authors also recommend that
pH is another factor that should be measured during the acclimation period, to ensure
that accurate baseline data is recorded.
2.5 Characteristics of the Test Organism
Another important factor that plays a fundamental role in the reproducibility of a
feeding experiment is the organism itself. Organisms of different age and sex may
behave or respond differently to contaminants. For example, juveniles are more
Feeding Behavioural Studies with Freshwater Gammarus spp.: The. . .
9
10:14 h (Garcia-Galan et al. 2017) (see Table 1). Adopting different light/dark cycles
could make the comparison between studies challenging, since light could influence
the organisms’ physiological processes and behaviour (Perrot-Minnot et al. 2013).
2.4 Media Selection
The type of media selected for an experiment is another factor that could have an
impact on the outcome of a study. Some researchers prefer to use an artificial
medium (see Table 1) that guarantees standardisation (Agatz et al. 2014; Maltby
et al. 2002), and in other studies, river water is sometimes used as a medium.
However, river water might be contaminated, and this could therefore interfere
with the organisms’ cleansing process during their acclimation period, which
makes it a peculiar choice of test media. Numerous studies have also used river
water or a mixture (Alonso et al. 2009; Blarer and Burkhardt-Holm 2016;
Bundschuh et al. 2009, 2017; De Castro-Català et al. 2017; Dedourge-Geffard
et al. 2009; Gergs and Rothhaupt 2008; Iltis et al. 2017; Maul et al. 2006; Zubrod
et al. 2015) (see Table 1). For example, Bundschuh et al. (2017) combined river
water with tap water, which also has limitations as the tap water could be contaminated (Magi et al. 2018). Potentially, any type of water could be contaminated,
which is why the authors recommend that researchers should report the chemical
breakdown (i.e. presence of contaminants) of their chosen water media along with
their study findings so that any contamination is transparent.
Gammarus pulex allocates up to 11% of its energy supply to osmotic regulation
(Sutcliffe 1984), and Gammarids have been proven to be acid-sensitive (Gammarus
fossarum; Felten and Guerold 2001; Gammarus pulex, Sutcliffe and Carrick 1973).
In fact, acidic conditions induce a range of physiological and behavioural alterations,
such as a reduction in the ventilation activity of Gammarus pulex (Felten et al.
2008b). These findings highlight the importance of measuring pH, as a shift in pH
might influence the outcome of an experiment and prevent comparisons between
studies. pH is rarely reported and presumably not measured in the environment
during the collection process, the acclimation period or the experiment. Along with
the chemical parameters of the acclimation media, the authors also recommend that
pH is another factor that should be measured during the acclimation period, to ensure
that accurate baseline data is recorded.
2.5 Characteristics of the Test Organism
Another important factor that plays a fundamental role in the reproducibility of a
feeding experiment is the organism itself. Organisms of different age and sex may
behave or respond differently to contaminants. For example, juveniles are more
Feeding Behavioural Studies with Freshwater Gammarus spp.: The. . .
9