The influence of insecticide exposure and environmental stimuli on the movement behaviour and dispersal of a freshwater isopod
Ecotoxicology
The influence of insecticide exposure and environmental stimuli on the movement behaviour and dispersal of a freshwater isopod
Jacqueline Augusiak 0 1
Paul J. Van den Brink 0 1
0 Alterra, Wageningen University and Research centre , P.O. Box 47, 6700 AA Wageningen , The Netherlands
1 Aquatic Ecology and Water Quality Management Group, Wageningen University and Research centre , P.O. Box 47, 6700 AA Wageningen , The Netherlands
Behaviour links physiological function with ecological processes and can be very sensitive towards environmental stimuli and chemical exposure. As such, behavioural indicators of toxicity are well suited for assessing impacts of pesticides at sublethal concentrations found in the environment. Recent developments in videotracking technologies offer the possibility of quantifying behavioural patterns, particularly locomotion, which in general has not been studied and understood very well for aquatic macroinvertebrates to date. In this study, we aim to determine the potential effects of exposure to two neurotoxic pesticides with different modes of action at different concentrations (chlorpyrifos and imidacloprid) on the locomotion behaviour of the water louse Asellus aquaticus. We compare the effects of the different exposure regimes on the behaviour of Asellus with the effects that the presence of food and shelter exhibit to estimate the ecological relevance of behavioural changes. We found that sublethal pesticide exposure reduced dispersal distances compared to controls, whereby exposure to chlorpyrifos affected not only animal activity but also step lengths while imidacloprid only slightly affected step lengths. The presence of natural cues such as food or shelter induced only minor
Locomotion; Dispersal; Automated video tracking; Aquatic macroinvertebrates
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& Jacqueline Augusiak
changes in behaviour, which hardly translated to changes in
dispersal potential. These findings illustrate that behaviour
can serve as a sensitive endpoint in toxicity assessments.
However, under natural conditions, depending on the
exposure concentration, the actual impacts might be
outweighed by environmental conditions that an organism is
subjected to. It is, therefore, of importance that the
assessment of toxicity on behaviour is done under relevant
environmental conditions.
Arthropod populations form an integral part of freshwater
ecosystems and are, as such, often exposed to chemical and
physical disturbances such as nutrients, pollutants, habitat
destruction and flow alterations (Dudgeon et al. 2006). In
agro-ecosystems, pesticides used for plant protection in
particular can enter surface waters through spray drift, run
off, and draining, and affect non-target animal populations.
Hence, environmental risk assessments are required for
pesticides to minimize undesired side effects. Standard
tests comprise a battery of mortality, immobilization and
reproduction studies on single species in the lower tiers of
the assessment process. In the higher tiers, micro- and
mesocosms may be employed to evaluate ecological
community responses to different exposure concentrations
(Brock et al. 2006).
To improve the determination of ecologically relevant
risk levels, behavioural endpoints are increasingly
investigated in ecotoxicological studies (Rodrigues et al. 2016).
They have been shown to be relevant and useful in acute
and chronic environmental risk assessments because they
link physiological functions with ecological processes.
Behavioural endpoints are also very sensitive towards
environmental stimuli and chemical exposure (Dell?Omo
2002), and several studies assessing the environmental
risks of pesticides reported behavioural effects at
concentrations significantly below those causing mortality (for
examples see Bo?ttger et al. 2013; Agatz et al. 2014).
Locomotor behaviour is particularly vital to animal life as
it facilitates feeding, predator avoidance, reproduction, or
migration, and thus may link the effects of individual stress
to the population level (Bayley et al. 1997). This type of
behaviour can be studied easily via video tracking
(Augusiak and Van den Brink 2015; Rodrigues et al. 2016).
In aquatic environments, relocating macroinvertebrates
are likely to encounter contaminated stretches with residue
concentrations of pesticides. Depending on the mode of
action and concentration of the encountered pesticide,
travelling animals may be affected and their movement
behaviour may be likely to change under such conditions.
Especially neurotoxic substances might adversely affect
orientation and activity. The observed alterations in activity,
furthermore, correlated with the measured contamination
gradient. Baatrup and Bayley (1993) showed that
cypermethrin exposure disrupted the general movement pattern and
activity of the Wolf Spider Pardosa amentata. However,
studies on the behavioural effect of toxicants on aquatic
crustaceans, so far mainly focused on feeding responses
(Bo? (...truncated)