Timing of sub-lethal insecticide exposure determines parasite establishment success in an insect-helminth model

Dhakal, Suraj; Meyling, Nicolai V.; Pedersen, Kathrine Eggers; Cedergreen, Nina; Fredensborg, Brian L.

doi:10.1017/s0031182019001331

Cited by 4 publications

(4 citation statements)

References 36 publications

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“…Implications for Risk Assessment under Global Warming. Despite increasing indications that the exposure order may play an important role in ecotoxicology, this has been mainly limited to studies combining toxicants (e.g., ref 7, but see ref 63), and never for the studies combining toxicants with the many and widespread abiotic natural stressors. We here provide the first evidence at the interplay of ecotoxicology and global change biology that the exposure order can strongly change how an important climate change factor magnifies the toxicity of a pesticide, and how the pesticide reduces the heat tolerance.…”

Section: ■ Discussionmentioning

confidence: 99%

The Exposure Order Strongly Modifies How a Heat Spike Increases Pesticide Toxicity

Meng

Delnat

Stoks

2020

Environ. Sci. Technol.

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The exposure order may strongly affect the impact of stressors, yet is largely ignored for the frequently occurring combinations of toxicants with natural stressors. We tested how exposure order shaped the interactive effects of serial exposure to the pesticide chlorpyrifos and to a heat spike in the larvae of the mosquito Culex pipiens. Notably, the chlorpyrifos-induced mortality was much more magnified by the heat spike and a synergism was already detected at the low concentration when exposure to chlorpyrifos followed the heat spike. This suggests that the preceding heat spike weakened the larvae as reflected in their lower net energy budget, moreover the chlorpyrifos-induced inhibition of its target enzyme (acetylcholinesterase) was only magnified by the heat spike when it was the first stressor. Also the chlorpyrifos-induced reduction in heat tolerance was stronger when the pesticide pulse followed the heat spike, and was buffered by the heat spike when this was the second stressor. Our results provide the first evidence that the exposure order can strongly change the magnifying effect of an important climate change factor on the toxicity of a pesticide. This highlights the importance of exposure order in ecological risk assessment of toxicants under realistic combinations with natural stressors.

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Section: ■ Discussionmentioning

confidence: 99%

The Exposure Order Strongly Modifies How a Heat Spike Increases Pesticide Toxicity

Meng

Delnat

Stoks

2020

Environ. Sci. Technol.

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“…A higher gut parasite load by Nosema spp. has been detected in honeybees exposed to imidacloprid (Pettis et al 2012 ), and likewise, more tapeworms ( Hymenolepis diminuta ) were found in mealworm beetles ( Tenebrio molitor ) following pyrethroid exposure (Dhakal et al 2020 ) compared to insects without insecticide exposure. Other studies suggest that the gregarine-infection level plays a crucial role in the effect of gregarines on their hosts, with higher loads causing obviously negative effects (Sulaiman 1992 ; Field and Michiels 2005 ).…”

Section: Discussionmentioning

confidence: 99%

Gregarines modulate insect responses to sublethal insecticide residues

et al. 2021

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Throughout their lifetime, insects face multiple environmental challenges that influence their performance. Gregarines are prevalent endoparasites in most invertebrates that affect the fitness of their hosts, but are often overlooked in ecological studies. Next to such biotic factors, a current common challenge is anthropogenic pollution with pesticides, which causes a major threat to non-target organisms that are readily exposed to lethal or sublethal concentrations. In a laboratory study, we investigated whether the presence of gregarines modulates the food consumption and life history traits of a (non-target) leaf beetle species, Phaedon cochleariae, in response to sublethal insecticide exposure. We show that the larval food consumption of the herbivore was neither affected by gregarine infection nor sublethal insecticide exposure. Nevertheless, infection with gregarines led to a delayed development, while insecticide exposure resulted in a lower body mass of adult males and a reduced reproduction of females. Individuals exposed to both challenges suffered most, as they had the lowest survival probability. This indicates detrimental effects on the population dynamics of non-target insects infected with naturally occurring gregarines that face additional stress from agrochemical pollution. Moreover, we found that the infection load with gregarines was higher in individuals exposed to sublethal insecticide concentrations compared to unexposed individuals. To counteract the global decline of insects, the potential of natural parasite infections in modulating insect responses to anthropogenic and non-anthropogenic environmental factors should be considered in ecological risk assessment.

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“…The impacts of pollutants' bioaccumulation on parasites appear to be complex and contextdependent (Rohr et al, 2008). For instance, in a terrestrial hostparasite system, the establishment of the tapeworm Hymenolepis diminuta in beetles was either increased or reduced by the exposure to an insecticide depending on the timing of the contamination (Dhakal et al, 2020).…”

Section: Costs and Benefits For Parasites In Polluted Environmentsmentioning

confidence: 99%

Benefits of Parasitism in Polluted Environments: A Review and Perspectives

Goutte

Molbert

2022

Front. Ecol. Evol.

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The frequency and strength of biotic interactions are thought to be shaped by environmental conditions. In this study, we reviewed and discussed the potential effects of toxic chemicals in driving shifts along the parasite-mutualist continuum. Some parasites have the astonishing capacity to accumulate trace metals and organic pollutants from various taxa within freshwater, marine, and terrestrial ecosystems. Recent studies have provided evidence of clear benefits for the host: when exposed to contaminants, infected organisms exhibited reduced contamination levels, less severe oxidative stress, and histological alterations, as well as higher body condition and survival rate compared with their uninfected conspecifics. Such effects might arise when the costs of parasitism are lower than their benefits in specific environmental conditions. Assessing the potential outcomes for parasites exploiting contaminated hosts is a crucial but neglected issue, since ecotoxicological effects on parasites may alter interspecific relationships. We identified possible avenues for future research using innovative tools and long-term experimental manipulations of both parasitism and pollution to better understand how toxic chemicals can modulate the strength and direction of host-parasite interactions.

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Timing of sub-lethal insecticide exposure determines parasite establishment success in an insect-helminth model

Cited by 4 publications

References 36 publications

The Exposure Order Strongly Modifies How a Heat Spike Increases Pesticide Toxicity

The Exposure Order Strongly Modifies How a Heat Spike Increases Pesticide Toxicity

Gregarines modulate insect responses to sublethal insecticide residues

Benefits of Parasitism in Polluted Environments: A Review and Perspectives

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