Combined exposure to parasite and pesticide causes increased mortality in the water flea Daphnia

Abstract

Organisms are exposed to multiple biotic and abiotic environmental stressors, which can influence the dynamics of individual populations and communities. Populations may also genetically adapt to both natural (e.g. disease) and anthropogenic (e.g. chemical pollution) stress. In the present study, we studied fitness consequences of exposure to both a parasite (i.e. biotic) and a pesticide (i.e. abiotic) for the water flea Daphnia. In addition, we investigated whether these fitness consequences change through time as a population evolves. Thus, we exposed Daphnia magna clones, hatched from dormant eggs isolated from different time layers of a natural dormant egg bank, to the parasite Pasteuria ramosa and the insecticide diazinon in a multifactorial experiment. While our experimental treatments for unknown reasons failed to induce disease symptoms in the Daphnia, we did observe a reduced survival of D. magna when simultaneously exposed to both the parasite and the pesticide. No increased mortality upon exposure to individual stressors was observed. We did not observe an evolutionary change in fitness response of the Daphnia clones hatched from different time horizons upon exposure to stressors.

Interplay between fungicides and parasites: Tebuconazole, but not copper, suppresses infection in a Daphnia-Metschnikowia experimental model

“…However, standard ecotoxicity tests determine the effects of single contaminants only, and may thus under- or overestimate hazards if interactive scenarios with other stress factors are not considered [ 2 , 4 ]. Contaminants that have no impact on organisms individually may be harmful when other stressors are present [ 4 , 5 ]. For instance, the sensitivity of organisms may be altered when they are simultaneously exposed to environmental changes [ 2 ], such as temperature increase [ 3 , 6 , 7 ] or reduced food availability [ 8 , 9 ].…”

“…Host-parasite relationships are strongly dependent on environmental context [ 22 ], and their outcome can be altered by the presence of natural and anthropogenic stressors, including pesticides [ 2 , 23 ]. Interactive scenarios between parasites and pesticide exposure have been shown to be mostly synergistic, causing exacerbated impacts on the host´s sensitivity to the pollutant [ 5 , 24 ] or on their susceptibility to infection [ 25 , 26 ]. However, this may not always be the case [ 27 , 28 ].…”

Temperature modulates the interaction between fungicide pollution and disease: evidence from a Daphnia-microparasitic yeast model

“…Agents of disease (parasites and pathogens) are important and ubiquitous biotic factors, playing an important role in natural populations by regulating host population dynamics, maintaining host genetic diversity and modulating other trophic interactions (Jokela et al 2009; Hall et al 2011; Agha et al 2016). Parasites can affect their host directly – for example through reduced fecundity, increased mortality and/or altered behaviour (Hall et al 2011; Kekäläinen et al 2014) – and indirectly – by inducing changes in the host's response to other stress factors, such as contaminants (Kelly et al 2010; Buser et al 2012 a ; Hanlon et al 2015). Research on the interactive effects of parasitism and contamination (reviewed by Marcogliese and Pietrock, 2011) has produced contrasting evidence, with the outcome of the interaction being favourable either to the host (Blanar et al 2010; Hanlon et al 2012) or to the parasite (Johnson et al 2007; Coors et al 2008).…”

Disease and pollution alter Daphnia taxonomic and clonal structure in experimental assemblages

“…Hanazato & Dodson, 1995;Folt et al, 1999;Sih, Bell & Kerby, 2004;Buser et al, 2012). The effect of multiple stressors has been investigated for many taxa across the plant and animal kingdom using different approaches: from studying the effect of stressors on single individuals and then extrapolating these findings to the community level, through mesocosms and field surveys.…”

“…It has been shown that a combination of abiotic and biotic stressors is often more harmful than either stressor alone (e.g. Hanazato & Dodson, 1995;Folt et al, 1999;Sih, Bell & Kerby, 2004;Buser et al, 2012).…”