Scientists conducted research using a library of over 1,000 chemicals to explore the effects of agrochemicals on insect populations. Their findings indicated that non-lethal levels of 57% of the chemicals influenced the behavior of fruit fly larvae, while elevated concentrations adversely affected their long-term survival following brief exposure. These effects intensified when the surrounding temperature was raised by four degrees.
While many people consider stink bugs, mosquitoes, and boll weevils unwelcome, these insects are vital for the ecological balance of our planet. The distinguished biologist E. O. Wilson famously stated that if insects were to disappear, our ecosystem would face collapse.
Researchers have observed shifts in insect behavior and a decline in their populations, averaging a decrease of 2-3% annually. This trend has prompted investigations into potential causes, including habitat destruction from overdevelopment, climate change, and the use of chemicals.
Recently, EMBL researchers and their partners studied the impact of pesticides, herbicides, and other agrochemicals on insect populations. They systematically exposed fruit fly larvae to a range of over 1,000 compounds found in EMBL’s unique chemical library, designed for large-scale testing of agrochemicals.
The larvae used in the study were sourced from various locations, and researchers examined their developmental stages, behavior, and long-term survival throughout their lifecycle. The study revealed that 57% of the chemicals tested caused significant behavioral changes in the larvae, even at non-toxic levels. Conversely, exposure to higher levels negatively affected the flies’ long-term survival.
“We discovered that even minimal doses of chemicals led to extensive changes in crucial physiological processes that influence development and behavior,” remarked Lautaro Gandara, the paper’s lead author and a postdoctoral fellow in EMBL’s Crocker research group. “The effects intensified when we raised the temperature in the growth chambers by four degrees, reflecting the increase in global temperatures and their potential influence on how pesticides impact larvae.”
The researchers initially increased the growing environment’s temperature by two degrees (from 25°C/77°F to 27°C/80.6°F). After observing little variation, they raised it again to 29°C/84.2°F, which remains within typical summer temperatures for many regions. At this temperature, they noted a significant effect.
“Additionally, we combined some commonly detected airborne chemicals at ecologically relevant doses and exposed fruit flies from the moment they hatched. This resulted in an even more pronounced impact,” stated Justin Crocker, EMBL Group Leader and senior author of the recent study. “We recorded a 60% decrease in egg-laying rates, indicating a potential population decline along with other changes in behavior, such as increased instances of hunching, a behavior rarely seen in unexposed groups.”
‘Hunching’ refers to the exaggeration of the larvae’s body position, which can indicate stress or distress and might signal underlying issues like toxicity, neurological disruption, or other physiological disturbances.
“Although hunching may appear trivial, even small behavioral shifts can influence fitness levels, particularly in areas like feeding, mating, and movement,” Crocker added. “It’s crucial for scientists to comprehend how animals interact with each other and their ecosystems to predict the consequences of changes such as habitat loss or climate fluctuations.”
The researchers noted they still do not understand whether hunching relates to other behavioral changes observed, such as the drop in egg-laying rates. However, it’s probable that larvae spending excessive time hunching instead of feeding will not thrive in their natural habitats.
Gandara and Crocker collaborated with other scientists on this project. Jean-Baptiste Masson and François Laurent from the Pasteur Institute, along with Christian Tischer’s team at EMBL, contributed AI-driven methods to analyze behavioral effects with high statistical accuracy. Other collaborators from EMBL included the Zimmermann Group, which provided the chemical library, the Savitski Group for proteomics expertise, and the Zimmermann-Kogadeeva group for computational biology.
Collaborators Vicky Ingham, a group leader at Heidelberg University Hospital, and Arnaud Martin, an associate professor in Biology at George Washington University, assisted EMBL researchers in broadening their studies to include mosquitoes and Painted Lady butterflies, where they found similar trends validating their experimental approach and findings.
“Insects, even those seen as nuisances, are indispensable to our planet. They pollinate our crops and are a fundamental part of the food chain,” remarked Gandara. “For years, many have speculated about the various factors influencing insect behavior changes, but this research highlights a significant contributing factor. A key takeaway from this study is that even small quantities of specific chemicals can have considerable effects.”
Insect behavior plays a vital role in sustaining the balance of ecosystems. Furthermore, as insect numbers decrease, genetic diversity also diminishes, which is essential for species to adapt to current and future environmental changes.
“The positive aspect of this study is that we have gained insights into which chemicals induce certain molecular and behavioral changes,” Crocker stated. “By providing information about the effects and toxicity of these chemicals, our findings could inform regulatory and industrial practices that more effectively safeguard human health and the environment.”
