Long-term effects of insecticides on environmental health: How does exposure of a female egg-laying insect to an insecticide affect subsequent generations?

Since early crop domestication, there has been an arms race by humans vying for optimal crop yields and quality, while insect pests continued to cause damage through feeding. Insecticides are a prominent class of pesticides, developed for the purpose of killing and dissuading insects from feeding on target crops. Despite abundant research on the effects of insecticides on various aspects of the (target) insect life cycle, we know surprisingly little about any possible transgenerational effects, especially in beneficial non-targets. Such effects could be of concern in an environmental and conservation context, whereby non-target insects could pass exposure-effects on to subsequent generations. Therefore, in this study we have investigated the effects of exposure to sub-lethal doses of widely used pyrethroid and neonicotinoid insecticides in an egg-laying butterfly; not only to her directly, but also the offspring’s development, survival, and host plant detection ability. In Bicyclus anynana (a popular butterfly model system), we have shown that LC50 doses varied greatly depending on the pyrethroid (deltamethrin, cypermethrin) and neonicotinoid (thiacloprid, imidacloprid, thiamethoxam) they were topically exposed to, and that sublethal doses may take time to have an effect. Furthermore, males appeared to be more sensitive, with reduced lifespans, which could affect those species that display protandry. We found that of all the insecticides tested, only deltamethrin significantly decreased female longevity. Additionally deltamethrin and thiacloprid also limited the number of eggs laid due to a shortened laying-period, however reproductive rate did not differ among all treatment groups. A transgenerational effect was observed, as offspring from thiamethoxam exposed females had a delayed development time, with offspring from deltamethrin and imidacloprid treated females having significantly reduced hatching success. All offspring from insecticide-treated females (except imidacloprid) were not effective at locating a hostplant. These results showed that whilst some effects could be observed after initial direct exposure to females (namely from deltamethrin), the most substantial sublethal effects were actually transgenerational rather than direct. Overall, sublethal doses of insecticides mostly did not seem to affect the females themselves in terms of longevity and egg-production, yet their offspring did appear to display consequences to their long-term fitness. Given that Lepidoptera inhabit a broad range of habitats, a substantial decline in population from a heterogeneous ecosystem could theoretically result in habitat degradations, due to the reduction of ecosystem services.

Grantor dc:publisher

Oxford Brookes University

Year dc:date

2023

Author dc:creator

• Hands, Jay Joseph S.

Contributors dc:contributor

• Breuker, Casper J
• Jones, Andrew K.
• Gibbs, Melanie

Statement dc:rights

• All rights reserved

Language dc:language

en

DOI dc:identifier

https://doi.org/10.24384/nf6w-f607

OAI identifier oai:identifier

tle:0cd6cc47-7eb7-42fb-ae42-4df765606331:d6bd9758-527a-46cd-bfe2-c433766e8fca:1